Layered Turning Manual

WOOD TURNING

Raymond Molinari

Translated from French by Robert Mari (Nice – France 2016)

Layered Turning Manual Contents

1 Whetting your appetite 5 2 Choice and wedding of the woods. Aesthetic research 14 3 Sketch drawing of the planned piece. How to choose the kinds of layers 1 A drawing is unavoidable 17 2 Tiered sketch drawing 19 3 Truncated cone shape (“trunconic”) sketch drawing 28 4 Pyramidal sketch drawing 39 5 Mixing of several kinds of layers in the same piece 47

4 Machining the basis units, the segments 1 Equipment and common points 50 2 Circular segment with band saw or scroll saw 64 3 Trapezoidal segment with circular table saw 66 4 Trapezoidal segment with miter saw 76 5 Pyramidal segment 81 6 Specific segments and « triangulettes » 89 7 Composite segment

5 Machining rings from discs. 1 How assembly the discs in order to cut them 107 2 Cutting rings with band saw 113 3 Cutting rings on the lathe. The « Troncoline » 121 4 Cutting rings with a scroll saw 140 5 Cutting trunconic grouped merlons. Cutting mixed discs 142

6 Assembling elements and layers 1 Gluing and clamping 148 2 Ring sprung from isolated segments or from blocks sprung from discs 149 3 First lathe mounting 156 4 Full or mixed layer 161 5 The open layer. The « guillotine » 167

7 Machining of the piece and its completion 1 Inner profiling or « hollowing» 179 2 Outside profiling of the wholly assembled piece 184 3 Sanding and finishing 188

8 Examples of realizations 1 And now let’s go ! 196 2 « L’Ecossaise (Scottish) » 197 3 « Les Deux Amar » (Two « amar ») 201 4 « Riemann » 205 5 « Méandros » 211 6 « Tête Bêche » ( Head to foot ) 215 7 « Quintette » (Quintet) 219 8 « Extra » and « Intro » vases 221

9 Appendix 1 Explanations about some words and abbreviations 226 2 Bibliography. Internet 227

1. Whetting your appetite

According to the dictionary, to layer means arrange in layers. You can tell, it does not get us very far. But yes, yes! We shall put together the layers (climb the stairs step by step, without getting breathless I hope).

Which wood turner did not dream to make a high vase with a narrow neck? Yes, but a big piece of a pretty wood with no cracks, is uncommon. Yes, but deeply hollowing gets very hard. It’s breaking your back. You can find really clever (and expensive) accessories to succeed in that, but the purists are reluctant to use them. And the purists are numerous.

Who has never craved, imagining bowls or vases, for assembling different woods, worrying about aesthetics?

How can you be deprived of the pleasure to decorate a piece with gaps, while harmonizing rare (and expensive) woods? And how to spare beautiful and rare woods while making great pieces?

THE SOLUTION: layered turning, you understood!

From my first steps in wood turning, I hoped to make an open work piece, and I made it, inventing a method combining piling segments and positioning them thanks to a jig (which I later named « marguerite »).

After a break of several years, I got a craving at the same time as I discovered out of English books (see chapter 9), wonderful items made in accordance with the technique of the layered turning, the principle of which is easy to define.

It consists in piling layers of wood, gluing and turning them gradually or eventually at the end of the gluing.

I came to find that the instructions in the above books were Incomplete.

I felt the need to go ahead in theoretical studies, and then imagine and create techniques of machining and assembling different elements which compose an item.

I am not pretending to teach you how to make beautiful layered items Through this manual, I should want simply to share with you my experiments and avoid you needless tests and make easier your work..

You may criticize my solutions, make them better, and... find other ones! We cannot test everything in a while. As for me, I followed my way successively from open working of circular segments to trunconic ones, then trapezoidal, and at last to pyramid shaped. It is your choice to go for the process that suits you the most.

Photos and figures are of my own, excepted the ones of Barnabé Ferré (BF), Claude Gaury (CG), François Delay (FD), Gérard Bidou (GB), Michel Havard (MH). All of them members of the Association « Autour du Bois ». I thank them heartedly. Gérard Bidou the first, for their friendly participation.

Which methods do you have in regards to layered turning?

The first one, rustic, not sparing with wood, consists in stacking slices, cut from a planed plank, slices drilled or not, matching or not different woods, and hollowing through or not these slices with a big bit on a column drill before sticking them, to make easier the centring when sticking, and then grinding. (Photography’s 1.1 & 1.2). I will not linger.

Photo 1.1

Photo 1.2

You can see underneath the flat view of such a slice. Nothing’s simpler.

Fig. 1.3

The circumference can be sawed or simply hewed. The lathe will do the remnants. The central hole, hollowed with a Forstner kind bit, makes the hollowing easier and allows the centring of the layers in regard to one another. We, have the double advantage of making an item as high as we want while using simple planks? We don’t need complicated jigs.

But if you want to work at the best the advantages of the layered turning method, you must stack as little wide as possible segments. Every set of segments arranged as a crown becomes a layer.

We shall write « full layer » when you can see no gap. The locution “open layer” means a succession of full spaces and empty ones. At last, a “mixed layer” is a double layer with a full layer and an open one. The word “ring” is reserved to full layer.

The layers can be straight or trunconic:

Straight layer section Trunconic layer section

(As depicted the inside and outer sawing slopes may be different)

Fig. 1.4

In the same piece we can find a composition of layers of several kinds, the choice resulting from the shape of the piece (see chapter “drawing”), from the aesthetics you look for and from the machining kind. Two kinds of machining are possible to create the layers: either by assembling segments (we could have used the word “prism” instead of “segment”) cut one by one, to use a French easily adapted to English (Diagrams hereunder A and B), or either cutting discs (diagram C)

The corresponding simplified flat views are the following ones: 7

A Full layers (crowns with butt-jointed segments)

Trapezoidal segments Circular segments

Fig. 1.5

B. Open layers (crenels and merlons)

Trapezoidal segments Circular segments

Fig. 1.6

About open layers, the name of the full part is « merlon », the name of the empty part is crenel, like at the top of a fortified castle... The presence of crenels allows creativity as to the shape of the merlons, the radial sides of which are possibly not straight or radial (brought into line with the center), as showed on the diagrams (see ch. 4.6 the example of such openwork item with S shaped merlons you can see from the top of it). You can make one by one straight segments, trapezoidal or circular ones (diagram A) with small planks or battens. This often happens when putting isolated full layers into an openwork item. The crown gluing then requires a great accuracy and skill. But the layers are much easier and quick to make if one cuts them in the discs as the following ones:

C. Discs allowing layers cuttings (straight or trunconic)

C 1 Triangles made discs C 2 Small planks made discs

Fig. 1.7

Please note that you can easily make isolated segments by dividing a layer from a C1 kind disc.

You can easily imagine all the opportunities of the layered turning method, considering only the different machining methods and compositions of the layers, but also thanks to the wedding of wood species and open working. Yet we shall take one more step forward while combining full layers and open layers to make mixed items.

In this manual, I shall not address the question of the “orange segment” or “(false) staves” assembling, despite very similar to the trapezoidal segments one. The flat sight of A kind in the figure 1.5 above is identical. The theory is the same one. But, on the other hand, the height of the layers is much higher with “orange segments”, often roughly estimated as the diameter or the height of the item. The ensuing segments cutting techniques are a little different. We work with the slant of the blade, but not with the slant of the plank regarding the blade. The thickness of the used woods also is different, more important. The « orange segments » assembling has only very often one layer of that kind. For these reasons, I quoted only this assembly which presents great possibilities as regards creation, as is showed below in the photography.

Photo 1.8 (CG) Example of an « orange segment » item. Walnut and hornbeam woods. 25cm high, 28 cm diameter.

In order to sharpen your appetite, please find here a few simple examples of layered turning achievements. Apart of the ones which are in the different following chapters, you can find many other ones, more difficult to make, more beautiful, more … everything... through internet (see chapter 9.2).

Photo 1.9 Simple stacking of thick planks cut discs. Maple and mahogany woods. 48 cm high.

Photo 1.10 « Diabolo » pieces of furniture. Wild cherry wood. Trunconic crowns and holed discs. Tops made with spindle (Also see photos 1.1 and 1.2)

Photo 1.11 Beech wood and amaranthine openwork. Separated straight circular segments and full layers “Daisy” kind positioning. 9 branches (see photo 6.5.6). 42 cm high.

Photo 1.12

Openwork 5 woods. Trunconic segments from a disc made with triangles glued on a martyr disc with intermediate paper. ”Guillotine” positioning (see chapter 6.5). The top crown with cocobolo segments. 27 cm diameter.

Photo 1.13 Two mixed cherry and rosewood (palissander) layers, and cherry full ring made of circular segments with a 45° angle to the center. One used the leftovers of the “intro” workpiece in the chapter 8.8.

Photo 1.14 (CG) Trunconic rings bowl. Cade and wenge. 26 cm diameter, 12 cm high Disc of planks. Variable conicalness.

Photo 1.15 (BF) Trunconic openwork layers bowl. Constant conicalness. Framire, niangon, walnut. 16 cm high, 36 cm diameter. 30 segments rings.

Photography 1.16. The « Esses » bowl. Example of curved open “triangulettes” (see chapter 4.6)

Photo 1.17. Two « Daisies » From only one “ triangulettes” disc.

I hope this manual will be your starting point to the creativeness or the link to the layered turning and to the wonderful achievements it makes possible and which are still to discover, in spite of the research work already performed by the “aficionados” all over the world.

2. Choice and wedding of the woods.

Aesthetic research.

The number of segments in a layered item may be very large, until several hundred (it is the case of an eight layers item, 40 segments a ring). This technique allows, thereby, woods associations and permits graphic or polychromatic different arrangements, juxtapositions, alternations, gradations, spirals, contrasts, geometrical patterns in accordance with your tastes, imagination, and a few.. know-how. Associations are well-chosen, other ones not..

Anyway, you must use perfectly dry woods, if possible kept before cutting, in a habitable room during about one month, as do the cabinet-makers.

Using woods of not very different (of a similar enough) technical performances is to be preferred: under the gouge, when sanding, when sticking, under finishing agents.

In other words, a good preliminary knowledge of the used woods is advisable. Your skill to handle the gouge or to sharpen it will not be enough perhaps to solve all the problems of coexistence between the woods. In the same spirit, you will avoid to work end grain and against the grain (see about this topic the opportunities given by the “triangoline”, chapter 4)

Go around your workshop, your shed, your mates’ stock, and plane a plank of each wood you have. Maybe apply a finishing agent in order to stand out better the tinge. You can so compare them, choose the ones you like and make up a diagram of the affinities (and more if as in some spots) you will find again to plan other items.

Here is, as an example, first the display on your workbench of available woods

Photo 2.1

Then, the list of your preferences, in order to carry out a vessel combining 5 or 6 different woods. Every line is a possible combination, with the positioning order. The last one was chosen (wenge, laburnum, cocobolo, maple, walnut):

wenge maple cocobolo wild juniper laburnum oak walnut amaranth padauk Olive cherry 1 2 3 4 5 6 1 5 4 2 3 6 1 5 4 2 3 6 1 5 3 6 4 2 3 6 4 2 5 1 1 4 3 2 5

Chart 2.2

A graphic composition such as a frieze will get an advantage from appearing over a contrasted background, for instance ebony over sycamore. Elsewhere, well matching tones assembling asks a more subtle research. Or the successive layers of a slender work piece, changing gradually from dark to light colors, stress the dynamics.

We must moreover take notice of the action of time and light and consider their long- range effects over the appearance of the wood. Many woods become darker while ageing. The most typical example is the one of the padouk, color-red when worked, getting gradually dark brown.

The aesthetics of the piece, besides its general structure, depends also to a large extent, on the quality of the finishing.

In the case of openwork design, which is a distinctiveness of the layered turning, we shall take notice, right from the conception, of the sanding difficulties. If the outside shape may generally be sanded on a moving lathe while setting the sanding strip on the piece, without damaging too much the ends of the segments which are apart a gap, the things are very different as to the inner shape. You will have to be experienced to the sanding techniques “lathe off”, which inner shape and curvature could be. Still in the case of openwork, you must think very early of the difficulties of sanding and applying a finishing coat on the sides of the out-of-reach segments which are lining the gap. Kinds of small tunnels. Shall we spray varnish, apply any product with a brush very patiently, or prevent the difficulty while finishing the “sides” when assembling the layers?

Another specificity of the layered turning: the choice of the height of the layers. With a general shape given, we can make use of few very high layers or many low layers. You will have to make a choice. You are alone in front of future work.

An indication, nevertheless. When we look for a special design stemming from the colors of different woods, small sized segments seem to be necessary. It is specifically true when one wants design a spiral running round the piece. It is true also to get diamonds or triangles.

And what about thinking of the link between diameter and height of a layer in one piece? Must we respect the absolute proportions (I double the diameter, I double the height), another rule (why not the square root of the diameters ratio) or no rule at all. With the experience, we can only conserve the third proposal «freedom, dear freedom..! ».

The application of a proportions rule between diameter and height of the layers may even be disastrous when a sudden change of the curvature of the piece outline occurs. Let us note that on the technical level, it would complicate the matters (needlessly), but would not be insuperable. We might, for instance, even when «trunconic» working, which is not appropriate for it, (see ch. 3.3), reduce with a gauge on the lathe the height of the layer we just glued, and so forth, as we have a maximum limit, the one of the initial disc.

Let us end by the layout of the joints between the segments, from a layer to another one. Must we bring them into line in accordance with a meridian of the piece or contradict them? Aligning is in theory possible, but very difficult to be respected when making. There is no point to consider the matter if the crowns are glued separately. And even in the case of trunconic works, where the basic technique is very favorable, there is little chance you will succeed. The slightest difference when building the upper side of the previous layer, or the slightest difference while centring each crown to another one, and you can forget it! The sturdiness of the piece is the winning argument, under machining, or finished. The space between the joints makes up as many small «bridges» which maintain the mechanical continuity between the layers. And, anyway, you will have no choice if you decide to make an open piece. So, no continuity of the joints from a layer to the next one, unless absolutely and exceptionally necessary as regards aesthetics. ;

3. Sketch drawing of the planned piece How to choose the kinds of layers

3.1 A drawing is unavoidable

Regarding “monoxyle”(single wood) pieces, made of a one wood block only, some turners spare themselves from a preparatory drawing. They have everything «in their mind», and do not compel themselves to follow an accurate plan. Very often the wood and its flaws command, when it is not a thoughtless gesture, not to write clumsy. We could name that method a «natural» turning, «by the feeling». Others are easily satisfied with a rapid sketch, a simple front elevation or a brief perspective, no precise scale respected.

But as soon as the piece becomes more complicated, for instance a bowl to become a box, a precise drawing is necessary. This drawing is the sketch of the completed piece, the whole of the different views (elevation, faces and sections) which make possible to describe it, unequivocally, with its shapes, its colors. That way of doing is far more simple, accurate and practical than drawing a complete perspective view according to the rules of the book, rules which are very complicated. Here the concerned sketch is a little different. It is the one coming just before the turning, the drawing of the sketch ensuing from the gluing of the different geometrically simple units. We could name it also «assembly sketch»

That sketch may make possible for you to know accurately, in the same time through the drawing and through the indication of the dimensions, the height of each layer and the rough diameters (before turning) of the crown relative to this layer, the detail of the composition of each layer with its own parameters (segments number N in a ring, open working, colors…) the exact dimensions and angles of the different segments. You will find later in this manual the examination of the machining of all those units, but it affects surely your aesthetic choices. That’s wholly indissociable. You can always do some cursory perspective sketches, even partial ones in order to visualize the completed piece.

The difference between the so defined both stages (rough sketch and completed piece) is so marked that one can, especially when making «pyramidal» works, turn two very different pieces from a same sketch drawing.

There is a mathematic rule shared by every sketch you should not forget: «homothecy (change of scale) preserves the angles». What does it mean and of use is it? The result is, in our case, the possibility of changing the scale of a drawing without altering the different angles we try to visualize, then reproduce, be affected by this change of scale. The scale 2 drawing, for instance, is homothetic with the one of the scale 1. The different angles which are between the straight lines are the same,

17 even though the length of the segments was multiplied by 2. The reduction makes possible to draw a large piece with a drawing board and a standard sheet. The enlargement makes possible winning accuracy either over the angles or the dimensions, the thickness of the pencil line does not depends on the chosen scale.

Good drawing needs good equipment. We shall heartily recommend for you to use a drawing board available to receive A3 sheets at least, if possible with a swiveling square you will appreciate in the event of «trunconic» pieces (see chapter 3.3). Here is a sample:

Photo 3.1.1

We shall consider one after the other, in the ascending order of difficulties of the drawings, the case of tiered layers, and then the one of trunconic layers. And later, the pyramidal layers. We shall write at last a few words about the mixed layers and the repercussion of the choice of the different kinds over the design of the completed piece before the final turning.

It is not forbidden, quite the reverse, to mix in one piece, open layers, full layers, and trunconic, tiered, pyramid shaped, mixed ones. Once you are given the basic techniques of making each kind of layer, the dialogue will be established by itself between creation and execution. And you will realize that the possibilities are unlimited, at the scale of your imagination and the one… of your lathe! You will not forget, reading the following chapter, that the drawing in question is the one of the piece sketch before the different turnings, including intermediate turnings under gluing.

3.2 Tiered sketch drawing

We have described in the chapter 1 what a ring made of trapezoidal segments is (fig. 1.5).

Let us pile that kind of rings in some layers one on top of the other, while changing the different parameters: we get a sketch shaped like successive bleachers, «step- like ». Under some conditions, we can insert in that sketch the design of a piece of a wider range of outlines, which is specific in that turning technique, unlike the trunconic technique. Here is a sample:

Fig. 3.2.1 (GB)

This example is doubly interesting, for it shows we can face up to sudden changes of curvature and we can decide a variation of the height of the layers within a great extent. As a matter of fact, we begin to draw the inside and outside outlines of the planed piece, then we look for the best as possible arrangements of the bleachers, while considering in the same time the aesthetics, the wood at our disposal, the technical constraints. This example shows a sudden curvature change is very logically linked with a gluing plan between layers.

The basic constituent element is the trapezoidal segment the flat view and the askew section of which along the median axis are as follows:

Fig. 3.2.2

You can read the following notations: - α is the half «angle in the centre», the angle from which we can see the trapezoid from the center. - N is the number of trapezoids, or segments, in a full ring - R is the maximum outside radius of the ring and r is the minimum inside radius, both after the making circle turning of the bleachers of the outline - B is the size of the large base of the trapezoid - l is the width of the ring before profiling measured in a horizontal position - L is the width of the batten (or small plank) in which the trapezoids are cut.

The dimmed parts vanish when turning, which converts the trapezoidal segment into a circular segment, then into a trunconic one, and then ….

On the left A figure, the L width plank in which we cut the segment is horizontal. On the right B figure, it is vertical, and this segment merges with a pyramidal segment the splay angle «i» of which would be null, or with an “orange segment”.

The case « A » is the most common. The «B» one is for instance convenient to make the median layer of a full piece while joining two flared shapes derived from «trunconic» method.

Let us now go one after the other through the different parameters which describe every segment, being confined to the general case « A ».

The layer height «h» raises only one problem: the limits of the machine at our disposal. 20

In the general case, the angle from the center written «2 α» is the outcome of an aesthetic and practical choice at the same time, the one of a whole number of segments in a ring; noted «N». All the segments of a crown being in a full ring, the relationship between α and N, is very simple: α = 180°/N. (The half angle in the centre α is very useful, when machining, hence the choice of that notation). he things become a little more complicated when we match segments of different angles in the centre; but not very much. Each group will have its own angle in the centre, and we will have to respect the same rule: while matching the groups we must have a total of 360°.

Are we free to choose the whole number N? Yes, theoretically, but no practically. Suppose N large enough (aesthetic choice), 25 for instance. Every segment has two radial faces (radiant, directed towards the centre) we will have to cut according to the angle α. A 1/10th mistake is not very much, and then as we have to make 50 cuts according to the same adjustments on the machine, so if you do not balance the mistakes, the error piled up in a ring is 50 times 1/10th of a degree , that is 5°. It is very too much to be made up by trimming 2 only segments to find again 360°.

So, we are brought, for machining reasons, to choose N in a first time among the even numbers, multiples of 2 (4 faces to be caught up). Yet, this way compels for us to test and adjust half rings, and it is still overall more practical to make it over quarters of rings, which makes possible to share the total error among 8 faces. That is to say, in the above case, 5 times 1/8th of a degree a face, this may be acceptable without damaging the aesthetics of the ring. So, we shall prefer N multiple of 4: 8, 12, 16, 24…This instruction is still even more valid in the case of pyramidal piece.

Things being what they are, we are not at all forced to keep N from a layer to another. A top ring « N8 »can for instance bring to an end an « N24 » piece or more.

Let us go on with the examination of the parameters of segments sizing and go to the width L of the plank, or the batten in which we will cut the trapezoids of a same ring. The drawing and only the drawing includes the changes of the profile along the height of the considered layer and gives us the minimal width « l » before turning (fig.3.2.1). We must add the width «d» of the figure 3.2.2. Actually, the turning of the inner profile erodes the width L, and especially as N is small. The value d is unimportant when N is more than 16. A few millimeters more will be sufficient then, without questioning too much, but without any exaggeration not to use wood needlessly. When N is less than 16, we can either draw a segment (a great precision is unimportant if we have taken notice of a narrow margin of error, very useful when turning), or apply the exact general formula: d = r (1-cos α) in which « r » is the inner imposed radius measured out of the drawing.

So your batten must be systemically wider than your ring, hence the interest to know « d » in advance, before cutting the batten, chiefly when working with precious woods. Actually, the error margin or safety margin of the turning is the most important in most cases to decide on the width L of the batten from the width “l”. Increasing this width allows us to respect more easily the chosen R in the end.

You will have sometimes to increase N (thus reduce α) for your ring to be fitted into the batten at your disposal. (When N is getting bigger, the chord moves closer to the arc of the circle and there is less wood lost when turning. Write a drawing, you will realize)

Let us end by the width B of the segment base. This is a main machining data. You need to know the B value accurately for you to carry out a set of N segments, which, after being fitted together, form a ring keeping to the required outer radius R. This preciseness must be especially great as N is big. This value can be directly measured out of a drawing of the following kind; you will have to make for every layer:

Fig.3.2.3 (GB)

Note, we can show in the same drawing practically every layer of the workpiece, provided that N does not change. One segment a cell and a layer. Radius change, but not angle from the center.

We increase the precision by increasing the drawing scale, multiplying the measures and working out the average. But that is long and boring. Better is (one occasion makes no custom) for us to trust the math brains and calculate B. The formula is very simple: B = 2 R tg α

Supposing we know how to use it, we have not always closed at hand a calculator for applying this formula. Yet you must peremptorily have in your workshop an ordinary pocket calculator to make « basic »calculations: +, - , : , x, should be only to add or deduct measurements.

It is then possible to work out B with no difficulty (plain multiplication) from this same formula written as follows: B = b R as the coefficient b (equal to 2 tg α) is given wholly ready in the following table:

Trapezoidal segments Table of the values of « b » enabling the calculation of the large base B of the trapezoid from R, outer radius of the ring and N, segments number in a ring B = bR

N 2α α b

Segments Angle in the centre Half angle in the centre multiplier number in a (B= b R) ring 6 60° 30° 1,155 8 45° 22,5° 0,828 10 36° 18° 0,650 12 30° 15° 0,536 16 22,5° 11,25° 0,398 20 18° 9° 0,317 24 15° 7,5° 0,263 28 12,86° 6,43° 0,225 32 11,25° 5,63° 0,197 36 10° 5° 0,175 40 9° 4,5° 0,157 44 8,18° 4,09° 0,143 48 7,5° 3,75° 0,131 52 6,92° 3,46° 0,121 60 6° 3° 0,105

Tableau 3.2.4 (RM)

When N is great, it is possible to find an approximate enough value of B while dividing by N the perimeter 2 πR (you can check it as N is 36 and over).

You have now a sufficient knowledge to build easily a draw of a tiered sketch and above all to size the segments of the different rings.

But the layout of the tiered trapezoidal segments is also and over all the mosaic art. You can have tremendous fun; you can increase as you want the layers, the number of segments in a ring, the colors of the woods. The combinations are unlimited, chiefly if you insert here and there composite segments or crenels (read further).

In order to check the intended effects, you may make the colored drawing of the finished piece. Here is a sample:

Fig. 3.2.5 (GB)

Fig. 3.2.6 (GB)

This kind of drawing is by itself a work of art, as we take care of the coloring. Drawing it asks for skill, preciseness, patience. Almost as much than building the piece, with some little exaggeration! Something to dissuade you from using this technique.

You will get almost the same result while making an extremely simpler, stylized drawing allowing for you to foresee with not much imagination the effects of the colors, spirals, diamonds, friezes… and amend them at leisure in a short while. Better it is to waste paper than one’s time or wood. 24

To depict the developed area of the piece, one shall agree to give the same diameter to every layer, we get a rectangle. This rectangle is crisscrossed. All the layers are as high as one another. Every layer is divided up into as much segments as included. One chooses a vertical line, a departure meridian, the beginning or the middle of the pattern. This grid is supposed to show the stylized piece. Every square receives a color corresponding to the chosen wood, and so we get the following drawing which makes possible to determine the different segments of each wood, layer after layer.

Fig. 3.2.7 (GB)

Addition of a plank between the segments

What happens when we add a small plank of any unchanging thickness "p" ("p" as plank, but the small plank may be very thick) between the radial segments?

Nothing as regards the angle α which is preserved (the edges of the plank are parallel to the edges of the trapezoidal segments fitting around them). On the over hand, this makes a ∆R increasing of the ring radius

We have two manners to look at the layout of this drawing: - Either we add a full small plank on one side only of the base trapezoidal segment, and we get a real dissymmetrical composite segment (fig. 3.2.8) which does not keep to the rotational symmetry - Or we add a half plank on every side of the trapezoidal base segment and we get a symmetrical fictitious composite segment. (fig.3.2.9)

Fig. 3.2.8 Real composite segment « trapezoid + 1 plank»

Fig. 3.2.9 Fictitious composite segment «trapezoid + 2 half planks»

To avoid confusion, the notation R is kept to the radius concerning the base segment.

We notice that the isosceles triangles O1 A C (fig.3.2.8) and O2 D E (fig.3.2.9) have the same vertex angle 2 α and their bases are as long. So they are identical and so have the same height, which is the radius corresponding to the two composite segments, R + ∆R.

Both presentations have their advantages as we will see. You have to choose between them in accordance with the problem you are setting. Do you want for instance for you to know ΔR from p, or the inverse? We shall find that the fictitious segment is better than the real one when we work open layers because it is radial.

When we make rings from composite segments «plate (small plank) + trapezoidal segment» (fig.3.2.8), we must take care of the space between the different segments when gluing, otherwise we lose the rotation symmetry and this may be embarrassing if at the edge of a piece. To avoid this, the easiest is inserting a trapezoidal segment between two «plate + trapezoidal segment + plate», and chiefly gluing while keeping to the ring sketch (see ch. 6.2).

The drawing is very well as α and p are great, it becomes promptly inadequate and inaccurate when they are reduced. The calculation comes to your help. If you do not fear the calculator, it is actually as easy and more precise to anticipate by the calculation the increase of the radius corresponding to the addition of a plate, for it is easily proved that ΔR = p /2 sin α The most common practice consists in fixing the value of the base B of the trapezoidal base segment, red in the figures, while the parameters α (or N), p and (R + ΔR) were chosen.

If the calculation is chosen, we begin by ΔR while applying the above relation, then R equal to (R + ΔR) – ΔR through a simple subtraction. And we finish by B=2R tg α. It is rapid and efficient !

If you choose the drawing, you will get a better precision by increasing the scale, scale 2 for instance.

We begin drawing the circle the radius of which is R + ΔR measured on the drawing (vertical section of the sketch), then we draw two radiuses of the same circle at an angle of 2 α. We draw the base AC of the composite segment, then the small plate at a chosen breadth by drawing a parallel line to one of the sides of the segment and we get directly the sought width, measuring AB without getting through the value of R. In this case, the presentation is the most practical.

This same figure 3.2.8 shows nevertheless, if we draw the next segment, that there is a trap. Rather than a long speech, better it is to watch what happens at the point C. To get from a composite segment to the next one, we cannot trust the angles of the base of the successive trapezoidal segments. There is actually a gap ε notice of

27 which we must take, by extending in your mind the base of the trapezoidal segment «through» the plate. (The value of ε is obvious in the figure: ε = p tg α. ε is to be neglected in practice only if a thin veneer is inserted between the trapezoidal segments).

We should so provide a little longer board; otherwise the point C would be in «an empty space».

The solution is giving up the figure 3.2.8 to the benefit of the layout 3.2.9 without drawing it. So the board will be as long as the side of the trapezoidal segment. The angles of the composite segments will be perfectly equivalent, which will make easier their assemblage, and then the assembling of the ring which will keep its rotation symmetry. Assimilating the layouts of the figures 3.2.8 and 3.2.9, which are complementary, is very useful.

When N is great, α is small. The increasing of the radius ΔR become very big, even for adding a thin board, and we must take care, as soon as at the time of the sketch, not to trust one’s intuition. That high increasing is not surprising: we add many boards, and the perimeter is getting noticeably bigger. Hence the interest of ∆R.calculation.

Here now you are well equipped to plan a tiered piece. If impatient, you may leave the remainder of the chapter 3, but that would be a real shame. You would deny additional extra dice to acquire complementary and not opponent techniques.

3.3 Truncated cone shape (“trunconic”)sketch drawing

You could surely go on to the truncated cone shape (I name “trunconic”, translating from French) technique and leave this chapter, but I don’t recommend it. A minimum theoretical knowledge will spare you quite a lot of disappointments and avoid for you to follow dead ends. The manufacturing of a trunconic piece is not at all instinctive.

But in fact, what is a trunconic ring? It is the volume included between two parallel planes and two revolution cones of same axis perpendicular to both planes. In practice, it amounts to cutting a ring in a board, splaying the cutting lines. If we pile such rings, we get either a higher truncated cone, or a succession of truncated cones in which we can include a curved shape. Theoretically, we can get so any shape, but the process is limited, if we want to keep the whole further listed advantages.

Here is a sample of drawing. In this example, one disc is cut, and the thickness of the rings, ensuing from this process, remains unchanged. We see further, it’s possible to make it vary, but it makes the drawing a little more intricate. On purpose, the drawing was much uncluttered, in order to keep only the basic essentials, common to all the drawings, even for the most complicated pieces. 28

Fig. 3.3.1

A layer forces the next one, and we choose the direction of the sketch construction, «rising up», in the present case.

Here, the splay angle becomes smaller and the piece is «closing». In practice, you would be well-advised to arrange the layers from bottom to top (as in a building, here from «a» to «g») which is corresponding to the inverse of the sawing sequence, which begins from the greatest diameter to the smallest one. This is also the assembling progression of the piece, as you will read further, and that convention is perfectly convenient.

The sawing «O» is unnecessary. The rim of the top edge can be worked with the lathe and this increases flaring possibilities. The sawing «1» gives the ring «g» The awing «2» gives the ring «f» and so forth.

We note at once that the raw thickness of the piece, before turning, is not unchanging all along the profile of the sketch. We can make thinner the transverse thickness of some rings, hoping spare a little wood, but test it, and you will be disappointed.

This manner to draw up a drawing offers numerous advantages: graphic simplicity, optimization of the gluing area before turning, continuity of the shape so much inside as outside, a larger freedom for you to choose the profile when turning the volume between those two surfaces, or to make up an unlucky gouge stroke.

The unchanged thickness of the sketch can only match with a straight profile. We notice also then the juxtaposition of perfect diamonds ensuing from the keeping of the cutting angle from a layer to the direct next one, the outer line becoming the inner line, and vice versa.

Laws commanding the lay-out of such a drawing are unavoidable.

1° First, the law stemming from the most frequent use of the table saw to cut the discs. The device diagram is the following one:.

Fig. 3.3.2

It is advisable to understand that the angle between the machine table and the horizontal, the splay «i» of this table (fig.3.3.2) is equivalent to the angle between the saw blade and the perpendicular to the disc to be cut, that we shall name the splay angle. The more this angle is large, the more the piece is splayed.

The band saw tables leaning to more than 45° are rare, and the drawing of the piece is due to be drawn consequently. From 0° to 45° all the angles are possible. Beyond, you will have to change the device, either by leaning the bogus saw table in regard with the machine table (so adding the splay angles), or by making a specific

30 table, after dismantling the original one. The practical limit is given by the height of the saw passage. This makes possible theoretically to think of bowl shaped pieces of the following kind:

Fig. 3.3.3

Supposing solved all the sawing problems under those extreme conditions, the aesthetic qualities of such a piece are not obvious. The much splayed layers are revealing large even wooden areas. And chiefly, the smallest flaw in assembling and/or gluing a layer to the next one, or a mere sanding too heavy in places, will become exaggerated, and the meeting line will be rapidly far away from the perfect circle. According to all these reasons, we will deal in what is coming afterwards only with a maximum splay angle of 45°.

Let us close the brackets and come back to the above figure 3.3.1. We may, as noticed, change the angle from a ring to another one, and it is the only manner (limited anyway) to follow the curvature of the hoped profile of the piece without resorting to rings not derived from the disc we are cutting.

No need to limit ourselves to notable angles (15°, 20°, 30°…). No need to know now the value (degrees or grades) of the adjustment angle of the table. This angle is transferred directly from the sketch to the machine with a simple flanged bevel square, as we will see furthermore. It is an obtuse angle, included in a range of angles from 90° (straight cut, perpendicular to the disc, splay angle 0) and 135° (splay angle 45°). Memorize the First law: the splay angle is limited to 45° on purpose, and it may be varying along the profile.

2° To be able to keep the center of a disc from a sawing to the next one, we must begin cutting the larger diameter layer and go on, without leaving any layer up to the smaller ring. Second law: the sawing radiuses are getting smaller when cutting the disc.

3° An axis of the piece was drawn in the figure 3.3.1. From that axis, we will measure the sawing radiuses. We can work on the aesthetics of the piece, while keeping the same profile, by moving the axis of the sketch.

But we need to keep to a minimal radius, which is dependent on the sawing technique. In the almost general case of a band saw, it is difficult to work under 2.5 or 3 cm with a 6 mm blade. It is greatly sufficient; the lathe can take off the surplus if we want a very small base. The scroll saw makes possible surely to still shorten this radius the blade being very narrow. We have too that freedom with the «troncoline» (see ch.5.3).

The sawing radius is taken directly on the drawing with a straightedge, a caliper, or a simply compass. You have so to draw carefully with thin lines. A little mistake over the radius may be corrected by increasing or decreasing the next layer, but it is necessary to remain within reasonable limits, in the region of the millimeter. Third law: given a profile, the axis position must keep to a minimal radius.

4° Let us come up to the crucial point, a forth law, after some more explanations.

It is imperative for each layer to fit in the disc stemming from the cutting of the former layer and the gluing area must be large enough.. This is possible only within the splay limit shared by all the «trunconic» drawings which are ensuing from the combination of three elements:

- The already mentioned need of making possible to cut the next ring in the remaining disc, which must not be too small (but can be larger than strictly necessary)

-The raw thickness of the piece before turning and sanding (thickness measured perpendicularly to the profile, and not horizontally). This thickness is fixing in the same time as the gluing width (which is greater than it or at least equal), the resistance of the piece when turning, and the sturdiness of the piece when finished. - The height of the considered layer.

The outcome of this factors combination is the minimal splay angle imin we must peremptorily keep when passing from a layer to the adjoining one. (Except when working over 2 discs or more)

The most general drawing is the following one:

Fig. 3.3.4

The splay angles 1, 2 and 3 are different on purpose. The sawing C 2 is corresponding obviously in the same time to the inside face of the layer 2 and to the outside face of the layer 1. Don’t ever forget, even if obvious!

As written before, the sawing order is decreasing, and the order of the layers is increasing. It is a mere convention which is convenient when making the layers and when assembling the piece.

A gap, theoretically allowed, was drawn on purpose between C3 and superior C2. If we cancel the right side, the left one will be cancelled out of making, and the gluing area then merges with the upper side of the lower ring and the lower side of the upper ring, which are corresponding exactly, but for the sawing line. It is advisable for you to keep this layout which was chosen for the sketch 3.3.1.

Let’s go to the next step. (Fig.3.3.5) Now, let’s allow ourselves a layer height, say comfortable enough, 24 mm and we choose an 8 mm raw thickness. Let us change the splay angle decreasing it, from the maximum of 45° (left drawing).

As for this maximum splay angle, the lower ring juts out from what’s absolutely necessary to cover the lower layer. Consequently, this makes a gap between he points A and B. While decreasing the splay (central drawing) this gap is decreasing. At a moment this gap is cancelled out. We are in the right sketch. The points A and B are merging. We have then reached the minimum limit splay angle imin, and in the same time, we reached the best use of the disc.

Fig. 3.3.5

For the initiated, the mathematical translation of the general limit case is very simple – see the right drawing: sin imin = e/h (Read «sinus I minimal is equal to e divided by h». From the value of the sinus, we can infer the angle value thanks to a trigonometrical table).

So only the raw thickness of the piece and the layer height, both chosen by the wood turner, come to fix this limit angle.

For a minimal thickness, set for instance newly at 8 mm, a graphical illustration of the relation between the three variables e, h and imin is the following one:

Fig. 3.3.6 34

If we choose a different thickness e, we have to move the straight line E into a parallel to the vertical axis the origin of which is the point O. Respect carefully the same scale for e and h, otherwise the angle imin between the line P (P as «p»rofile) and the vertical axis would be wrong. If we look for more precision or a bigger easiness to note the limit angle, one can increase the scale of e and h.

If you choose to take a working thickness shared by all the pieces, one diagram is sufficient for all the drawings you will draw.

If you aim at one splay angle, the diagram gives you easily the minimal layer height to be respected in order to reach it (you have merely to draw the line P at the chosen splay angle. It cuts the line E at a point the distance of which to the point O can be measured. This distance is the sought layer height).

One may see at once thanks to this very simple geometrical construction that higher the layer is, the more it will be possible to get a slender work piece, while keeping the opportunity to splay it to 45°.

The lay-out of the work piece profile becomes freer when h is getting bigger.

The amateur in «trunconic» work pieces may also refer to the following chart, which is only a variant presentation of the basic trigonometric equation (sin imin = e/h)

Fig. 3.3.7

This chart allows you in a way to visualize the traps which you must not fall into when you plan a piece.

We can see immediately that the "allowed area" is not as big as hoped, that this area is cutting down when the layer height is decreasing, essential parameter; that it is a little increasing when reducing the decided limit thickness, with the known drawbacks.

Conversely, we can see that a reasonable layer height, smaller than 70 mm (this is not huge as regards mixed layers, for instance) allows very slim pieces. At last, if one brings this chart closer to the previous geometric construction (fig.3.3.6), we can see a last notion appearing, the one of the minimum height under which every drawing attempt is doomed to fail. This limit layer height is ensuing from the decided minimum thickness and from the 45° maximum splay angle enforced by the commercialized machines, and other constraints as written previously.

We can easily work out this minimum height: hmin = 0,707 e that is to have an idea, an 8, 5 mm layer height for a 6 mm thickness. Underneath, we fall into the field of the miniature pieces or into the one of the very thin pieces, which have their supporters.

We can so express the

Fourth law: there is a minimum splay angle imin to be respected peremptorily. Consequently, there is a minimum layer height hmin under which we fail utterly.

Let’s go on with the theoretical examination of the process.

According to the profile of the planned piece, you may have to use more than one trunconic cut disc. Wood saving is less impressive, but the other advantages of this process remain. Matching two discs made of different woods permits to make two pieces the alternation of which is inverted …etc.

A closed shape is given by assembling two open shapes, which makes easier the" hollowing" and requires at least 2 discs, and more generally a joining ring.

In fact, we observe that the minimal layer height is about 12 mm. Underneath this height, the raw thickness of the piece becomes very small and the gluing area much reduced. That’s convenient, for less than 12 mm thick planks are not qualitatively perfect. They often become distorted. The one who looks for an aesthetical result which needs very small segment heights, can resort to the composite discs technique ensuing from gluing of thin discs one on top of the other. In the same time, so we free the shape of the piece, which is not that

36 bad. Otherwise, we have to keep to a 45 °neighboring splay angle. At the end, we get tired, even if the drawing in the different colors is particularly successful.

Here you have another simple example (fig. 3.3.8), «clarified», of a simple shape drawing the lay-out of which was led unlike to the one of the above figure 3.3.1, «getting down the layers» to a splay angle which increases toward the top. The starting disc is strictly the same in both cases, and the shapes utterly different.

We note the jut of the upper ring can greatly free the shape of the upper edge and still increase the splay of the piece.

Fig. 3.3.8

And, to finish, what we can get from evenly thick discs (in this case squares) while simply playing with the splay angle.

Photo 3.3.9 (MH)

Anyway the «trunconic» technique is very attractive. Its advantages add to most of segmented turning ones.

- We are very much saving wood. We can, for example, make a 1 meter high vase with only one 85 mm thick and a 30 cm diameter disc!!

- We can match different woods without altering them and get notable effects. It is of course an advantage common to all the layered pieces, bur the trunconic cone technique brings an «asset» from a lonely composite disc including 24 half diamonds, we make in only one sawing operation, all at once, the cutting AND primary gluing of 192 segments, if the piece is eight layers high, and 576 segments if they are ensuing from a 3 layers composite disc!!!

But, what is the flaw of this process, which seems to have only advantages? The drawback is, when we look for a special chart, the repetition of the colours arrangement and of the proportions of the segments broadness from a layer to another one.

We can get the much liked effect as spiral or zigzag, while applying a rotation discrepancy from a layer to another one, but the chart freedom is much lesser than with layers made of trapezoidal separately assembled segments.

3.4 Pyramidal sketch drawing

Ever higher, ever stronger, ever slimmer, more…difficult ! But also freer as to the shape you want to make from simple wood off cuts. There is in fact another manner to come closer to the final shape of the turned volume which consists in making N facets (sides) hollow pyramidal trunconic layers, still from small planks, holding the already written advantages of wood saving and mixing of woods. In English, we use the word “stave”, “douve” in French, to name this kind of segment. Truly, it is near to a stave of a cask which would have been cut from top to bottom. But the pyramidal segment is plane when raw, while the stave of a cask is curved. Here the relationship comes to an end. The pyramidal segment becomes a part of a cask stave only after turning. The “pyramidal” processing is more complex than the “trapezoidal” one. In both cases, the small plank is worked flat. It remains in this position when glued during the trapezoidal processing, but on the other hand, slopes during the pyramidal processing to make a facet. In one figure, you can see two examples of pyramidal workable profiles. The blue profile of the work piece no more becomes integrated into a succession of tiered piled rectangles, but into a succession of slopping trapezoids, very close to the final shape.

Fig. 3.4.1

As a rule the wood worker, in order to regulate his machine, has not to know the numerical value, either of the angles, neither of the lengths he transfers directly with a bevel square or a caliper from the drawing of what he is making. The reason is very simple: getting as much as possible rid of sources of errors

Applying this rule to the «pyramidal technique» would only lead to disappointments, even if drawing very carefully all the details of a segment in every ring. The machining preciseness would not be sufficient enough for a ring to close accurately, unless an exceptional stroke of luck.

I cannot spare you now some mathematical explanatory expositions, being worried to close this chapter with a table of numerical values, and avoid you to resort to trigonometry.

The drawing of a pyramidal segment is not obvious, and the approach of the different parameters of the machine adjustments, can ensue only from several views, front view, on one side, in profile such as for instance, the following ones;

Fig. 3.4.2

The sketch of the piece having one or several pyramidal layers does not offer special difficulty. You will choose as you like while drawing it up: the layer height h, the thickness e, the increasing of which allows a greater shape freedom and the minimal value of which depends notably on the number N of segments in a ring, the radius R of the great layer base.

The pyramid axis, by agreement vertical, is common with the one of the planed piece.

The two sections which fix the «trunk» are horizontal, perpendicular to the axis, and separated by the layer height «h» measured on the axis. Three basis data derived from the plan itself are common with the «trapezoidal technique»: - layer height «h» - segments number in a ring «N» - maximal outside radius «R» of the ring.

The following data come to be added to those three base ones - Minimal thickness «e» of the plank in which the elements are cut. Unlike the trapezoidal technique, e cannot merge with h. Determining «e» is the same as «L» in the trapezoidal technique, and I’ll not come back over it. My advice: don’t be sparing too much wood! - Vertex half angle «i» of the pyramid which is equivalent to the average splay angle of the piece in the considered layer. From I, R and h, the small base radius stems from, but knowing it shows no interest at all as regards the machining.

Other parameters, connected to the previous ones, demand a notation. -The width «L» of the master plank in which the segments of a same ring are cut. This width is measured in accordance with the slope, and not anyway as per the horizontal.

-At last, the main feature of the «the pyramidal technique», which makes every difficulty: the machining of the segment demands knowing a couple of angle values, different from the alone angle α of the trapezoidal technique. According to the transfer process of the cutting angles on the machine, we will appeal to the couple (β, γ) (advisable) or to the couple (β, φ). The angle α remains useful, but is only an auxiliary parameter, not useful directly to the adjustments.

An explanation is necessary about the difference between the angles γ and φ. In order to understand this distinction, you must anticipate the machining of the segments (see ch.4). One of the two angles makes possible the splay adjustment of the blade in regard with the supporting table. That’s real as well with the table saw than the miter saw.

In order to make this adjustment, we transfer the angle measured on the sketch, or the angle calculated, with a mechanical or a numerical «bevel square». One leg leans against the table the other one against the blade. Moreover, the two legs must be located in a plane perpendicular to the table, which makes necessary an additional adjustment.

Yes, but what a solution to choose? Make the experience: if, when keeping the bevel square in a plane perpendicular to the table, you turn the leg sticking to the table, the other leg makes a variable angle to the blade. This angle is minimal when the vertical plane formed with the two legs of the bevel square is perpendicular to the blade plane. This is the angle φ, or «dihedral angle» of the mathematicians.

But don’t forget we are cutting a board leaning against a guide. And leaning a leg of the bevel square against this guide built vertically is much easier: it avoids looking for the perpendicular to the blade not materialized on the machine. If we lean against this guide, the adjustment angle is γ. In the practice of the pyramidal segment, all of us prefer it to the angle φ, whatever the math brains may think!

The notations have been purposely chosen similar to the ones of the trapezoidal segment, but let there be no misunderstanding about that! There are basic differences which make everything much complicated: the angle of each lateral side of the sketch with the plane of the segment (the one of the master board), the angle between the bases with the same plane, complementary to the previous one, the angle formed in twos by the edges of the lateral sides, the existence of two radiuses, one for each base are connected to the taper (or the splay as you want).

The views B of the above figure 3.4.2 make possible to know β and B, but give no information over γ (or φ). As regards the former adjustment angle γ, we have to draw up the following sketch, which is obvious enough I hope not to need lengthy explanations over its construction:

Fig. 3.4.3 42

The views of the figure 3.4.3 are less «speaking» by themselves than those of 3.4.2, but give us everything is necessary: β, γ, B and L. As to the angle φ, a specific sketch would be necessary (see fig. 3.4.4). A handwritten formula on this figure gives the theoretical value of L: L = h/cosi + (e-2ε) tgi

The presence of the small ε thick flat surface is ensuing from a convenient machining constraint. It is not necessary in theory (see chapter 4.5)

A last figure (next page), now in the space, makes possible to visualize correctly any pyramidal segment. The trigonometric relations (sine, cosine, tangent) between the different angles are given and explained in one page. They are outstandingly simple and very easy to use with a «basic» pocket calculator.

Like the trapezoidal technique, B = 2R tgα (hence the importance of coherent notations).

The direct application of these formulas makes you free of every constraint as to the choice of the basic parameters i and N. Nevertheless, as to machining and assembling considerations, the choice of N as a multiple of 4 is a good choice, even a very good choice.

Moreover, flared angle values i increasing by a 2,5° step make possible coming close enough to every drawing shape. So, if you’re totally impervious to the above trigonometric relations in spite of their simplicity (I ram home the point) the way of the pyramidal technique is not close. The below two entries table gives you at simple reading, for a couple (i, N), the values of « b », hence B = bR by a simple multiplication and the couple (β, γ) or (β, φ) you need to adjust your machine.

Let us take a concrete example by referring in advance to the chapter 4.5: Suppose your scheme has a 24 segment layer (N) with a 42,5 splay angle (i) and a 80 mm outside radius (R) for the big base of the pyramid trunk (see figure 3.4.3)

You can read on the table, as regards these parameter values, the adjustment following values, in the right process order.

1° ß = 5.08°,which allows to know the rotation angle between guide and blade, that is 90.00 -5.08 = 84.92° (see position F, figure 4.5.1). The hundredth of degree is not strictly necessary, but gives a tendency as regards the accurate adjustment direction.

2° γ = 5.54° ; This allows the splay adjustment of the blade, on its left side, at the angle 90.00-5.54 = 84.46°

3° b = 0.263 ; This makes possible the calculation of the width of segment great base. So B= 80x0.263= 21 mm. Then, we can adjust the position of the width stop, after making on the test small plank a first slanting cut with the 1° and 2° checked adjustments.

Fig. 3.4.4 44

Table 3.4.4 (1) (MH et RM)

N 8 12 16 20 24 28 32 36 40 44 48  22,50 15,00 11,25 9,00 7,50 6,43 5,63 5,00 4,50 4,09 3,75 b 0,828 0,536 0,398 0,317 0,263 0,225 0,197 0,175 0,157 0,143 0,131 i  2,07 1,34 0,99 0,79 0,66 0,56 0,49 0,44 0,39 0,36 0,33 5,00  22,42 14,95 11,21 8,97 7,47 6,40 5,60 4,98 4,48 4,08 3,74  22,41 14,94 11,21 8,97 7,47 6,40 5,60 4,98 4,48 4,08 3,74

 3,09 2,00 1,49 1,18 0,98 0,84 0,74 0,65 0,59 0,53 0,49 7,50  22,33 14,88 11,16 8,92 7,44 6,37 5,58 4,96 4,46 4,06 3,72  22,30 14,87 11,15 8,92 7,44 6,37 5,58 4,96 4,46 4,06 3,72

 4,11 2,66 1,98 1,58 1,31 1,12 0,98 0,87 0,78 0,71 0,65 10,00  22,19 14,78 11,08 8,87 7,39 6,33 5,54 4,92 4,43 4,03 3,69  22,14 14,77 11,08 8,86 7,39 6,33 5,54 4,92 4,43 4,03 3,69

 5,12 3,32 2,47 1,96 1,63 1,40 1,22 1,08 0,98 0,89 0,81 12,50  22,02 14,66 10,99 8,79 7,32 6,28 5,49 4,88 4,39 3,99 3,66  21,94 14,64 10,98 8,78 7,32 6,28 5,49 4,88 4,39 3,99 3,66

 6,12 3,97 2,95 2,35 1,95 1,67 1,46 1,30 1,17 1,06 0,97 15,00  21,81 14,51 10,88 8,70 7,25 6,21 5,43 4,83 4,35 3,95 3,62  21,69 14,48 10,86 8,69 7,24 6,21 5,43 4,83 4,35 3,95 3,62

 7,10 4,61 3,42 2,73 2,27 1,94 1,70 1,51 1,36 1,23 1,13 17,50  21,56 14,34 10,74 8,59 7,16 6,13 5,37 4,77 4,29 3,90 3,58  21,41 14,29 10,72 8,58 7,15 6,13 5,36 4,77 4,29 3,90 3,58

 8,06 5,24 3,89 3,10 2,58 2,21 1,93 1,71 1,54 1,40 1,28 20,00  21,27 14,13 10,59 8,47 7,05 6,04 5,29 4,70 4,23 3,84 3,52  21,08 14,08 10,56 8,45 7,05 6,04 5,28 4,70 4,23 3,84 3,52

 9,01 5,85 4,35 3,47 2,88 2,47 2,16 1,92 1,73 1,57 1,44 22,50  20,94 13,90 10,41 8,32 6,93 5,94 5,20 4,62 4,16 3,78 3,47  20,70 13,83 10,38 8,31 6,93 5,94 5,20 4,62 4,16 3,78 3,46

 9,93 6,46 4,81 3,83 3,18 2,73 2,38 2,12 1,90 1,73 1,59 25,00  20,58 13,65 10,22 8,17 6,80 5,83 5,10 4,53 4,08 3,71 3,40  20,29 13,57 10,18 8,15 6,79 5,82 5,10 4,53 4,08 3,71 3,40

 10,83 7,05 5,25 4,18 3,48 2,98 2,60 2,31 2,08 1,89 1,73 27,50  20,17 13,37 10,01 8,00 6,66 5,71 4,99 4,44 3,99 3,63 3,33  19,84 13,27 9,97 7,98 6,65 5,70 4,99 4,43 3,99 3,63 3,33

 11,70 7,63 5,68 4,53 3,77 3,22 2,82 2,50 2,25 2,05 1,88 30,00  19,73 13,06 9,77 7,81 6,50 5,57 4,88 4,33 3,90 3,54 3,25  19,35 12,95 9,73 7,79 6,49 5,56 4,87 4,33 3,90 3,54 3,25

 12,55 8,19 6,10 4,86 4,05 3,46 3,03 2,69 2,42 2,20 2,02 32,50  19,26 12,73 9,52 7,61 6,34 5,43 4,75 4,22 3,80 3,45 3,16  18,83 12,61 9,47 7,58 6,32 5,42 4,74 4,22 3,79 3,45 3,16

 13,36 8,74 6,51 5,19 4,32 3,70 3,23 2,87 2,58 2,35 2,15 35,00  18,74 12,38 9,25 7,39 6,16 5,27 4,61 4,10 3,69 3,35 3,07  18,27 12,24 9,20 7,36 6,14 5,26 4,61 4,09 3,68 3,35 3,07

 14,15 9,26 6,90 5,51 4,58 3,92 3,43 3,05 2,74 2,49 2,28 37,50  18,19 12,00 8,97 7,16 5,96 5,11 4,47 3,97 3,57 3,25 2,98  17,67 11,85 8,90 7,13 5,94 5,10 4,46 3,96 3,57 3,24 2,97

Table 3.4.4 (2) (MH et RM)

N 8 12 16 20 24 28 32 36 40 44 48  22,50 15,00 11,25 9,00 7,50 6,43 5,63 5,00 4,50 4,09 3,75 b 0,828 0,536 0,398 0,317 0,263 0,225 0,197 0,175 0,157 0,143 0,131 i  14,91 9,77 7,29 5,81 4,84 4,14 3,62 3,22 2,90 2,63 2,41 40,00  17,60 11,60 8,66 6,92 5,76 4,93 4,31 3,83 3,45 3,14 2,87  17,05 11,44 8,59 6,88 5,74 4,92 4,31 3,83 3,45 3,13 2,87

 15,63 10,26 7,65 6,11 5,08 4,35 3,81 3,38 3,04 2,77 2,54 42,50  16,98 11,18 8,34 6,66 5,54 4,75 4,15 3,69 3,32 3,02 2,77  16,39 11,00 8,27 6,62 5,52 4,74 4,14 3,68 3,32 3,01 2,76

 16,32 10,73 8,01 6,39 5,32 4,56 3,98 3,54 3,19 2,90 2,65 45,00  16,32 10,73 8,01 6,39 5,32 4,56 3,98 3,54 3,19 2,90 2,65  15,70 10,55 7,93 6,35 5,30 4,54 3,97 3,53 3,18 2,89 2,65

 16,98 11,18 8,34 6,66 5,54 4,75 4,15 3,69 3,32 3,02 2,77 47,50  15,63 10,26 7,65 6,11 5,08 4,35 3,81 3,38 3,04 2,77 2,54  14,98 10,07 7,57 6,07 5,06 4,34 3,80 3,38 3,04 2,76 2,53

 17,60 11,60 8,66 6,92 5,76 4,93 4,31 3,83 3,45 3,14 2,87 50,00  14,91 9,77 7,29 5,81 4,84 4,14 3,62 3,22 2,90 2,63 2,41  14,24 9,58 7,20 5,77 4,81 4,13 3,61 3,21 2,89 2,63 2,41

 18,19 12,00 8,97 7,16 5,96 5,11 4,47 3,97 3,57 3,25 2,98 52,50  14,15 9,26 6,90 5,51 4,58 3,92 3,43 3,05 2,74 2,49 2,28  13,47 9,07 6,82 5,46 4,56 3,91 3,42 3,04 2,74 2,49 2,28

 18,74 12,38 9,25 7,39 6,16 5,27 4,61 4,10 3,69 3,35 3,07 55,00  13,36 8,74 6,51 5,19 4,32 3,70 3,23 2,87 2,58 2,35 2,15  12,68 8,54 6,42 5,15 4,29 3,68 3,22 2,87 2,58 2,35 2,15

 19,26 12,73 9,52 7,61 6,34 5,43 4,75 4,22 3,80 3,45 3,16 57,50  12,55 8,19 6,10 4,86 4,05 3,46 3,03 2,69 2,42 2,20 2,02  11,87 7,99 6,02 4,82 4,02 3,45 3,02 2,68 2,42 2,20 2,01

 19,73 13,06 9,77 7,81 6,50 5,57 4,88 4,33 3,90 3,54 3,25 60,00  11,70 7,63 5,68 4,53 3,77 3,22 2,82 2,50 2,25 2,05 1,88  11,03 7,44 5,60 4,49 3,74 3,21 2,81 2,50 2,25 2,04 1,87

 20,17 13,37 10,01 8,00 6,66 5,71 4,99 4,44 3,99 3,63 3,33 62,50  10,83 7,05 5,25 4,18 3,48 2,98 2,60 2,31 2,08 1,89 1,73  10,18 6,86 5,17 4,14 3,46 2,96 2,59 2,31 2,08 1,89 1,73

 20,58 13,65 10,22 8,17 6,80 5,83 5,10 4,53 4,08 3,71 3,40 65,00  9,93 6,46 4,81 3,83 3,18 2,73 2,38 2,12 1,90 1,73 1,59  9,31 6,28 4,73 3,79 3,16 2,71 2,37 2,11 1,90 1,73 1,58

 20,94 13,90 10,41 8,32 6,93 5,94 5,20 4,62 4,16 3,78 3,47 67,50  9,01 5,85 4,35 3,47 2,88 2,47 2,16 1,92 1,73 1,57 1,44  8,42 5,68 4,28 3,43 2,86 2,46 2,15 1,91 1,72 1,56 1,43

 21,27 14,13 10,59 8,47 7,05 6,04 5,29 4,70 4,23 3,84 3,52 70,00  8,06 5,24 3,89 3,10 2,58 2,21 1,93 1,71 1,54 1,40 1,28  7,52 5,08 3,83 3,07 2,56 2,19 1,92 1,71 1,54 1,40 1,28

Adding small planks between the segments

The results obtained in the case of trapezoidal technique when we add a plate between the side faces of the segments (see the above chapter 3.2) remain applicable to the pyramidal technique and so I’ll not linger: the angles are preserved, but the radius is increasing. (Refer to the figures 3.2.8 and 3.2.9).

Conclusion

In short, long explanations for a very simple conclusion, in the form as a beautiful table which should engage you to the way of pyramidal technique, should it be by curiosity. However, in my opinion, it would be risky for you to go on into this technique before having taken the tiered one and assessed the difficulty to close a ring, even flatly. To begin, test first on common woods boards. Beech, maple, are right at all.

The theory gives you «falling into your lap» the data to be given to your machine. YOU have to learn to enforce them by drawing from your skill and imagination possibilities. Once, after having overcome the machining difficulties, you will feel a very great satisfaction when assembling your first pyramidal layer. It’s magic... as the turning!

3.5 Mixing of several kinds of layers in a same piece.

A preferential way of execution we’ll examine in the next chapters corresponds to each method, tiered, trunconic or pyramidal we examined

Time and preciseness of execution, depend to a great extent on this execution way, what might be your skill.

After long and meticulously preparing the base disc, what a pleasure in cutting, in a short while, trunconic rings with your band saw! When «blank piling» as and when we cut, we get at once a full-sized (and colored) sketch of what the finished piece will be, with no too much distortion.

Nothing to compare with the time you need to cut, then put together separated segments in an alone ring.

Combining various full or open layer kinds ensued from tiered, trunconic or pyramidal methods makes possible to execute, unreservedly, all the shapes of one-wood turning, trunconic, flat or pyramidal segments, with no greatest difficulty other than your patience. Every flaring or slimness is possible if we don’t confine ourselves to a trunconic cutting of a single little thick disc.

Mixing makes freer the shape of the piece with no limitation on the diversity of the woods and the assembling of the segments.

Besides we add to the array of the turned items those which have flat sides: it’s not forbidden anyway for instance to include into a piece one or several pyramidal layers or simply trapezoidal ones we keep unchanged in the finished item.

You’re free therefore to draw a piece the shape or the size of which you like and forget almost completely the wood constraint. No need to rise up on the lathe some 30 kg of wood to make a 40 cm high vase! It does not matter whether the cocobolo log you have is 15 cm sized if you want to make a 30 cm diameter bowl.

Nevertheless, a constraint and a very great one: you will remain in the field of voluntary turning in which the wood does exactly as you please.

You will not feel the pleasure to make beautiful and great wood shavings. The whole turning is all delicacy, light, floating. You will not experience the pleasure of hollowing out a pretty burr walnut, or make a natural rimmed vase from a heather root. Your pleasure will be of different order, more mental. And it will be increased tenfold when you have controlled the basic techniques and matched them to make THE item you dreamed of!

Among those basic techniques, I’ll mention one which you’d pay special attention to, because often it will make your work easier, but you must foresee from the very stage of the sketch. It’s a very practical open technique.

The practice consists in arranging and gluing on a full disc evenly spaced out «triangulettes», which will become merlons. The disc and the «triangulettes» are cut in the same time with a band saw. It is sufficient to glue the two pieces of the ring, to sand the base on an abrasive plate, and we find very quickly a mixed layer ready to be assembled. So in one time, we position the merlons of several layers, while keeping the same layout (spaces, colors, veining …) from a layer to the next one. Try it and you will make it yours!

At last, you can conceive, at the stage of the sketch, pieces with complementary layers.

So the two bottom layers in the above photography 1.13 are the two top unused layers of the vase «intro» in the chapter 8.8.

Moreover, both pieces in the chapter 8.8 are typical samples of the full/open mixed layers we just wrote of. A palissander (rosewood) merlons layer (dark) comes after a kiln dried wild cherry layer (light) and both are linked into a mixed layer. Two discs were sufficient to make this close shaped vase.

In a same open layer, a short merlon comes after a long merlon; this layout is strictly respected from a layer to the next one due to the trunconic technique.

They are also samples of mixing between trunconic mixed layers and full trapezoidal layers: the three median «Intro» layers (chap. 8.8) and the top layer of 1.13 are of this last kind (rings of trapezoidal segments). See below another sample.

Photo 3.5.1 « Méandros » 25 cm diameter.

The previous piece deserves a few explanations. Visit the following, please!

The first layer, a simple full ring making the foot. Bubinga. The second one, 8 triangulettes full disc referenced N8 The third and fifth ones, a N12 trapezoid ring. The sixth, a N16 trapezoid ring, N is high as to the small broadness of the disposable wood. Palissander. The fourth one, the climax of the show: N44 composite ring, palissander and «white» of carob tree, thinly textured. The number 44 ensues from the division of the chosen diameter (250 mm) by the pattern of the Greek frieze. (17,5 x 17,5 mm).

The different techniques are at your disposal. They will be further detailed. It's up to you!!

4. Machining the basic units, the segments

4.1 Equipement and common points.

You’ll find in the recent literature (ch.9) many samples of layered turned pieces including complex composite segments which are by themselves small masterpieces involving the mastery of very difficult techniques asking for boundless patience.

Remain humble and begin by the beginning, repeated machining of individual segments intended to make full or open layers. At the chapter 5, we shall see how, in some cases, we can machine a whole group of segments in the same time.

Except for the" triangulettes" (chapter 4.6) which have 5 sides, the other segments have 6 ones. Whichever the starting point, the sketch, the wood we have at our disposal… we find always ourselves before a carefully planned or roll sanded board, and so 2 sides are machined, temporarily at least. Most of the time, these sides vanish when gluing the different layers. The lathe takes care of the 2 tangential sides, provided the work is basically prepared.

Two radial sides remain. Both must make between them a precise angle, a very precise one when we aim for a full ring. The distance that separates these sides must also be precise if we want to respect the sketch diameter. Otherwise, we must provide a little more wood and balance when turning.

To make these two radial primal sides, you must have the required equipment according to your ambitions and… of the sketch kind you have chosen. In the listing of those tools, those which are not absolutely required are written in italics.

- Lathe. It does not play an essential part when machining the elements. Yet, it is useful, should it be to have only a good lapidary sander (lathe mounted). The size of the lathe and its performance do not matter, provided it does not vibrate. YOU have to match your scheme to the equipment you have, machines, chucks, gouges, etc. You will always find a design seducing you while taking notice of the equipment you have. And there are many useful or substitute accessories you can make by yours less expensively.

- Planer. A big machine is not necessary, for the wood work pieces are small. On the other hand, the preciseness is necessary. For instance, checking the thickness does not change from an edge to the other one of the planed board over the maximal acceptable width.

- Circular table saw. A 45° tilting blade, reclining usually to the right side. A double tilting is not necessary. Clearance height would be better 50 mm at 45°. The tray level with the blade is very practical, but it may be replaced by a routing table top fixed on a remote tray, and, our last resort, by a routing table top (sled) running in the slot of the table. The circular saw is necessary for instance for ripping in a strict parallel to the edges of the board, or rubbing the angles (see pyramidal segments) even if you make cross askew cuts to the radial. You will have to be careful to the quality and the state of the blade. Its sharpening will have to be flawless. The following test is instructive: cut a small dark hard wood board (palissander for instance) with a carefully cleaned blade. Every tooth must be colored. If some teeth remain shiny, they don’t work and you must appeal to a skilful sharpener. This occurs even with new blades!

- Miter saw. With or without sliding motion. The absence of runners is perhaps better, for it takes out a source of inaccuracy when sawing. The only going down movement is allowed. About the blade, same comment than when the circular saw. Test a sliding movement to check that the saw line is strictly rectilinear; that there is no gap or protrusion. In this case, avoid sliding movement, but the saw is forcing more. Nothing’s perfect. You will read further how to improve the trade saws, which are not made at first to cut trapezoidal or pyramidal segments with an angle preciseness over 1/10° degree.

- Band saw. It allows to make circular segments (see ch.4.2) and is chiefly fitted for cutting trunconic rings from discs (see ch.6.1) As to this last technique, a tilting table is almost necessary.

- Scroll saw. Such a saw may be very useful and take the place of a band saw. But its cutting power as to height and quickness is much lower and the thickness of boards or discs to be cut is limited.

- Router. The addicts of the router are full of possibilities and imagination. In the scope of my experimentation, this magic tool has not (yet) found its place.

- Disc sander. If you have not a stand-alone bench disc sander, make one. And if you have one, you can perhaps extend the diameter of the disc, which favors a better work. And moreover, you may choose a not too great quickness, not to burn the wood. Make an investment in an extremely cheap faceplate (it’s available) on which you will fix permanently a 30 to 40 mm thick medium disc. Face the front side on the lathe, and/or work by wedging between the chuck and the medium disc. Glue abrasive jointed strips on the disc, with vinyl glue, for example. Take care for on the contrary to the appearances, the disc sander is «aggressive» enough and for this kind of use, it’s better to take a light abrasive, beyond 120 grits. The supporting table may be also in medium. It may be equipped with a rod inserted into the saddle (banjo) of the lathe, or lean against the bench through a wooden structure. This table must be square to the disc. To protect yourself against a wrong even minor squaring when you aim to a sides connection, keep the habit of labeling a «facing»

51 side of the element you are working with, choose between the two manners of working the next figure and change no more not to make a mistake. Either the reversal takes place during the machining, or it is made during the assembling. Don't pile up these two operations.

Fig 4.1.1

The same process is also commendable when you work with a circular saw, miter saw or none.

- Sanding roll. Here still you can find a machine in the trade, or machine yourselves this tool moved through the lathe The simplest one is made of a table swiveling around an axis in a parallel to the lathe axis. Here is an example:

Photo 4.1.2 (CG)

Simple and efficient. A supporting plate, a plate swiveling around a continuous hinge and a sliding plate bearing the piece to be adjusted, the same for all the solutions. A cleat allows adjusting the gap between the piece and the sanding roll.

You can imagine many other solutions. Here is an example, conceived around the use of the… device of a piano stool! A rotation of the control handle and the plate moves vertically.

Photo 4.1.3 Misuse of an old piano stool

Another solution, more complex but accurate, with threaded rods. You must take into account the turns for the supporting table to remain in parallel to the cylinder axis.

Photo 4.1.4 (BF)

- Sanding table. This very cheap tool is essential. You may use it as well to make a light hand adjustment, horizontally on the bench, as vertically on the lathe to put the finishing touches to the front side. Take a melamine or medium plate, coat it with glue (white wood glue is working very well) and apply jointing abrasive straps (80 to 120 grits). That’s all. If you have a buddy joiner ask him for wide abrasive tapes. It’s better. Stop straps before the edges of the plate not to damage the bench of the lathe. On the bench fix the sanding table with two clamps, or between the grippers of the «parisienne» press (longitudinal workbench vice). Wear a no slip glove to protect your fingers, the segments being sometimes very small. Here you have an example of use of the sanding table on the lathe. The table hides the saddle which is adjusted to be used as a stop, which holds steady its position:

Photo 4.1.5 Sanding table positioned on the lathe

- « Stringeons ». In a dialect of the south of France, the «strindjoun», an open steel circle, made to order, is used by masons to hold tight two formwork planks or to hold firm a straight edge. Gallicizing this word, we have «stringeon» which reminds «astringent». A little semantics…Other French people name this tool «serrette» (“tightener”). As soon as we cut the segments from the waste block, we are brought to glue them basically to control the angles. A simple dry fit by butt jointing with no gluing brings nothing good. Apart from being satisfied with a mere clamping during a few seconds with a quick- setting adhesive (which works most of the time, you must know), you have to find the means to hold tight not parallel bearing faces which have the unfortunate tendency to slide when we use the usual clamps. The making of specific wedges solves theoretically the problem, but you will be rapidly annoyed by this process.

I offer you the following solution, successfully tested, but not valid for all the cases unhappily. A virtual straight line linking the two spikes of the stringeon must cross through the fixture and meet no blank spaces. Cut segments into bed base springs (the armchair springs are a little weak), which make an almost full circle. Take out the twist, cold working on a vice with a tong, for the two ends to be face to face. Shape the ends to a point by grinding (with a small grinding disc PROXXON for instance). The ends must be very conical and tapered for them to enter the wood lightly and don’t slip. For the ends to be lined up in a position of clamping, we must have a range of different diameters. See below an example of usage with pyramidal segments:

Photo 4.1.6

- Caliper and millimeter ruler, more convenient in this case than a measuring tape. A protractor is not very useful.

- Bevel square, or better digital bevel square, very flat, to follow closely the sketch drawing and to avoid the parallax inseparable of a classic bevel square.

- Flanged bevel square. You will not find it in the stores, and if you want to make trunconic cuts with a bandsaw, this tool is very useful to adjust the tilting of the table in regard of the blade. Here is an example, I imagined, made of «plexiglas» (Corian?) that makes the reading easier. See also chapter 4.5.

Photo 4.1.7 Plexiglas flanged bevel square. Both wings (bases) are sticking close to the drawing, which removes off the parallax error.

Photo 4.1.8 Plexiglas flanged bevel square, in the position to adjust the tilting of the band saw table. The base leans against the table and holds steady the flanged bevel square in the good position.

- Three- dimensional square

Here is again a tool you will not find in the stores, almost essential to test the different quarter turn waste fixtures, chiefly with pyramidal technique.

You can use a testing fixture of this kind with a flat angle different from 90°, for instance 60° with N = 12 or 24, but then you lose the generality. And is it so important to make 3 instead of 2, or 6 instead of 4 waste blocks? Moreover it is easier to handle on the disc sander and test the accuracy of a flat 90° fixture.

See below my Plexiglas prototype. The quadrants must be drawn on the base before gluing the three sides. They are invaluably helping to check the right geometry of the fixture (Ch.4.5). A preciseness of the right angles in the region of one tenth degree is desirable, to check with a digital square stuck in the angles. This is anyway the preciseness we can wish from a digital square.

Photo 4.1.9 Plexiglas three- dimensional square. Using this kind of a «frame» clamp makes easier gluing the three sides.

- A good lighting is too often forgotten. Now we can find 1500 and more lumen bulbs well lighting and giving out little heat.

- Work areas vacuuming, over lathe and lapidary. If it’s possible to manage without vacuuming up until profiling, it is strictly necessary during the process of sanding.

- A compressed air gun, to remove at the most the sanding dust from dark woods which gather into the pores of the light woods. I’ll write again on this important point in the chapter 7.3.

We are equipped now, and let us go to the working methods common to trapezoidal and pyramidal segments.

Reversal or back and forth method?

The first idea in mind to cut a board into trapezoidal segments is playing with the rotation of the board in regard of the blade (or with the rotation of the blade in regard of the board in the case of a miter saw), in a succession of back and forth motions, which needs plenty of adjustments, except that we used a tool I named «triangoline». I’ll write further (chapter 4) on this tool which is a double caliper with an in-house made protractor.

The cutting positions are very free, as shown in the following figure, if we don’t try to make identical segments, which is not strictly necessary. In fact, a trapezoidal segment can always be cut in a block included between two straight lines making the wanted angle 2α.This is allowed easily by the "triangoline", with only one sharp adjusting of the angle, which we will check for it to be unchanging from a segment to another one. Not even we read the size of the angle on the edge of the jig, but directly the number N of segments in a turn.

Figure 4.1.10. Back and forth method. Two over simple samples. See ch.4.3

This method is that of the back-and-forth motion. It is competitive with the «reversal» method (see further) as regards simplicity and wood consumption, when the woods are flawless. It is almost as precise and allows as needed to use a board - In which one edge only is required to be straight, and if we use the two edges as support on the guide, they are not necessarily parallel. - Which has flaws such as knots, worm holes, and so on, flaws avoided while choosing freely the area to be cut. This free choice allows also avoiding turning work against the grain. At last, we get rid so of the systematic effect of the «reversal», sometimes not wanted, of the upside-down reverse of the drawing of the board edges (confer the book of Malcolm Tibbetts «The Art of Segmented Woodturning» page 36) See about this matter the ch. 4.6 concerning the «triangulettes».

Tangential cuttings complementary of the segment derived from a back-and-forth motion can be curved, made easily with a band saw or a scroll saw, which is an additional advantage. This back-and-forth method offers so charms enough to prompt you to make your own «triangoline».

But the «reversal» method, almost immediately accessible with the equipment at your disposal is the easiest one. I mean the reversal of the board over itself (and not upside down), while keeping an edge against the guide. As when you are turning in your bed when you can’t sleep.

The guide is adjusted to the fixed angle 90° ± α or 90° ± β according to the case (see ch.3) We make a first cutting, face F 1 on top, we turn over the board, we slide it on the distance B (plus the saw kerfs’ width), we apply it well against the guide and we cut with the F2 on top. And that’s all! Quick, precise as far as possible, and efficient.

Figure 4.1.11 Reversal method

We may sum up with the following image: the reversal inverts the cutting angle, taking the board as a reference. For the method to succeed, both edges of the board must be straight and strictly parallel, otherwise, Mr Thales the geometer gets angry, and the method does not work.

If the blade is perpendicular to supporting table, we get a trapezoidal segment; if the blade is tilting, we get a pyramidal segment (See ch.4.5). The consequence of the reversal indeed is transposable to the blade tilting.

The drawback of that method, inherent in its advantage and common with the back- and-forth method, is precisely we have just to make one or two angle adjustments, and that the slightest snag recurs 2N times (N segments in a turn, let’s remember), with no statistic adjustment. Which leads us, as we will see further, to the peremptory

59 need to cut segments into a waste block and make the test glued fixture, in a quadrant, that is N/4 segments. The consequence of the reversal is not limited to this matter, as shown in the following figure.

Figure 4.1.12

The drawing of the board resulting from the veining of the wood, of its colours (heart or sapwood), of the matching of several woods, is inverted upside-down when assembling. The result is we have interesting possibilities as regards aesthetics. Here is, as an example, a one layer pyramidal piece matching rosewood, ash, wenge, bubinga (15 cm high). The reversing of the layers including several woods makes possible to get a design of superposed friezes.

Photo 4.1.13

From what is preceding, two laws emerge you must well bear in mind: As well in trapezoidal as in pyramidal techniques the reversal inverts the sawing angles and inverts upside down, when assembling, the drawing of the board cut into segments.

Composite board

Another common point in machining of segments is the trick of the composite board, to make 2, 3 or more segments in the same time.

Figure 4.1.14

Instead of being made with one wood only, the board includes battens, of the same thickness, not necessarily in the same wood, glued with a slit sheet between them. Anyway we will find again this simple and easy process of the slit sheet in the sequel of this manual.

Once the board is cut, it is sufficient to unglue the segments a, b, c from one another with a knife blade and a small mallet. Of course, the different wideness of the battens and bases ensuing from this process must be compatible with the drawing of the sketch (or the sketches, as working over several pieces in the same time can’t be prohibited). The paper glued on the sides is not embarrassing since the sides will be modified by turning.

How long the boards must be?

The question is not to be set, concerning the theoretical level, as regard the circular segments, as they are called (ch.4.2). They are drawn on the board(s) at our disposal, in any shape, and that’s all. It is not possible to foretell precisely the necessary minimal area. Anyway, this is not of great interest, wood off cuts and waste being minimal.

In the case of trapezoidal or pyramidal segments, the question presents not much interest when we work cheap woods we can have as we want in the required or approximate dimensions. That’s the case of waste boards. On the other hand, it’s not the same for «precious» woods, in every sense of the word. It is then very interesting to anticipate precisely and quickly the length of the board needed to make a ring, that is to say a whole turn, in the same wood. We may surely draw a design. But calculation is so much quicker and reliable!

To the average width of a segment, we must add the thickness of the saw kerf (at an angle). We must foresee an over length for the skew starting cut and about 60 mm to support the piece on the guide when sawing the last segment. At last, it is wise to provide 2 or 3 more segments for facing up to unpleasant surprises, wood flaws, sawing snag, one too many knock on the disc sander, etc.

I suggest you the underneath calculation, applicable to trapezoidal as well as pyramidal segments. The «radiuses» are measured on the sketch of the vertical cross-view of the piece (figure 4.1.15) which is the image of your aesthetic choice.

Trapezoidal segment Pyramidal segment Figure 4.1.15 Radiuses to be taken into account in the calculation of the minimal length of the board .

See beneath the table to be filled to get the wanted result in a few seconds:

Small inner radius =……….. Big outer radius =………. ______Total =……….

Total multiplied by ½ b =………. «b»directly read on the table 3.2.4 Add one saw line =……….. ______Total = ……… Multiplied by N + 2 or 3 =……….

Add over length to keep the piece on the guide, about 60mm =……….

Total minimal length of the board = ……….

Note : N is increased by 2 or 3 units as safety, hidden flaws of the wood, clumsiness and so on

Putting end to end

What are the solutions when we have no suitably long strips? In extreme cases, it is possible to go back over the sketch and reduce the dimensions of the piece. We may also multiply the number of the strips to make one ring only. Then we lose a little wood, the one of the machining over lengths.

The frequent solution is «putting end to end». We make a skew or right cutting at the end of the strip on the supporting side against the guide, and we make the same mirroring cutting on an end of a waste strip, which in substance has exactly the same crosswise section. We glue both of them with quick-setting glue (see ch.6) and everything is right. This «end grain» gluing as our Canadian friends say, is not very tough, but it does not matter. This fixture is short-lived and little requested.

Photo 4.1.16 Putting end to end sample with miter saw. Maple is less seldom than ebony.

A last common point remains :

Keeping to the segment base width.

We are still in the case when we want to make a series of identical segments as regards their geometry so that we end wholly or partly at a ring of a fixed diameter.

The base width B determines this diameter, the other parameters are set. A very great precision is not necessary, if N is not too big (a mistake of this kind is the same as adding or subtracting a" p" thick board equal to the adjusting mistake (see the end of the chapter 3.2) and if we have at our disposal a sufficient margin in the strip width to salvage the mistake by turning. Look back to the right side of the figure 4.1.10. When the board is sliding in order to position it before sawing the side 2, it is enough to lean it against a stop, at the distance B of the blade, this distance measured according to the axis of the board. Theoretically, it is sufficient to bring the alone angle to the stop. Anyway, this method is kept by several authors.

But practically better it is to lean all or a subset of the skew end of the board against a linear stop, in the same direction as the support side. We win so in precision and steadiness from a segment to another one. Simply we must not fall into the trap of a stop which would wedge the segment during the sawing or at the end of the sawing I’ll write again on these two points in the chapters 4.3 and 4.4.

To close this chapter, there are requirements, common to several segment machining kinds. Summon up your patience and your perseverance. Test your machines. None is perfect. Be precise in every adjustment. Don’t hesitate to make many waste fixtures.

4.2 Circular segment with band saw or scroll saw.

After those general observations, we will turn out to the simplest to make segment, the circular segment or curved segment, as you prefer. We begin by drawing on a cardboard to be easily cut, 2 concentric circles of R and R- l radiuses (see figure 3.1.2), then two radiuses making an angle 2α. A great precision of the drawing is not necessary, and the transfer of the angle on the protractor is sufficient, as regards the machining before gluing which will be following.

The cardboard template is cut, and then arranged at best on the prepared planed boards. The segments are drawn one after the other, avoiding the wood flaws and aiming to work with the grain when turning. Two samples follow:

Photos 4.2.1 and 4.2.2. Two samples of circular segments drawings

On the left (photography 4.2.1, steamed wild cherry), this kind of cutting allows to avoid the patent flaws of the board, and makes possible to work only with the grain.

On the right (purple heart): in spite of the choice of N = 4 (N is small), we can make a ring into a board the width of which is less than a half diameter. In this precise case, a segment taken from another board is to be added.

No problem for cutting with a band saw or a scroll saw, while saving a small margin beyond the drawing. It is better to anticipate before gluing and present gradually the sawed segments on a part or the whole of a ring drawing at the scale 1, drawn on a rescued «melamine» board, as underneath:

Photo 4.2.3

We will have still another advantage while working on the disc sander the radial sides as they come, in order for them to be plane, smooth and matching (the matching is checked when presenting the segments on the drawing). These three conditions must be satisfied to get a correct result.

On the other hand, it is not necessary for the crosswise sides of the segments to be perfectly radial, neither for the angle α to be strictly respected, above all if the ring is an intermediate layer, and even less if it is an open layer. This gives a little margin when working on the disc sander, but not too much, for the lack of precision has to be paid with the last segment.

The advantages of this process lie in the simplicity of the principle and in the opportunity to turn only with the grain. We will resort to it rather in the cases (happily infrequent for the nice woods) when the work against the grain is really too much hassle.

In regard with the trapezoidal segment, we are winning the adjusting of the device guide, but we lose the drawing of the scale 1 sketch which we cannot escape. By the

65 working time, the balance is neutral. We avoid so the making of a waste block, indubitable advantage when we have only a ring to make. On the other hand, the simplicity of the principle hides a real execution problem with the closing segment you will appreciate when working. To avoid that difficulty, and as with the other processes, you will have an advantage in choosing N a multiple of 4, and make tests on quadrants thanks to the three dimensional square portrayed in the chapter 4.1, first before gluing, and then after partial gluing of the quadrants.

4.3 Trapezoidal segment with circular table saw

The theory of the trapezoidal segment has no secret anymore for you since you have read attentively the chapter 3.2. You paid no less attention to the chapter 4.1…(?). Eager, you can surely dash into the adventure, and make your first rings and put into practice the method of the previous chapter concerning the circular segment, and use no more a band saw or a scroll saw, but a circular saw (stationary) to cut the radiating sides. Practicing so, very quickly you will get sick of segmented layered wood turning!

You have happily much better to do with your circular saw. Now you have the two boards made at the right dimensions, those of the final segments, and the waste checking board. You have only to enforce the best sequence to be sure the cutting will respect the angle α and the width B, and the board will become segments. How precisely you will cut those segments, and for a least part, how reliable your machine is, the quality of the hoped result is depending on: the closing of the ring but for 1 or 2 degrees. Under that condition the disc sander will make the remaining with no harming to the good aesthetic result.

There are hardly two methods to lead to a maximum preciseness you look for within a reasonable time: the reversal of the board, the principle of which was described in the chapter 4.1 and the back and forth with a «triangoline» which can also be used profitably in the application of the reversal method.

With a stationary circular saw (of course the portable one is forbidden), the wood is moving in regard of the blade, when with a miter saw it’s the contrary. Moreover, the blade surface of a miter saw swivels around a vertical axis, but not the one of a stationary saw. Practical differences are ensuing, which justifies two different chapters, but the principles are obviously the same.

The reversal and the sled

We have to arrange the board with the right angle in regard to the blade, adjust the length to be cut, and then keep this position during sawing. To operate these functions while keeping at disposal the saw at the cost of a brief assembly/dismantling process, we will resort to a sled, sliding in a parallel to the blade not loosening too much, horizontally and vertically.

A detailed blueprint of such a device would be out of the scope of the present manual, and… offer no interest, every machine having its own specifications. The board is put flatly and the blade must be perfectly squared in regard of the plane of this sled. Test cuts are necessary . According to the saw you have, the three following configurations may arise, and you will choose the most convenient means to fix better the sled on the potential slider:

Fig. 4.3.1 (RM) Three configurations of the stationary circular saw

A - Simply grooved table, with no slider (two grooves are better than one). The sled must have a tongue running in the groove, not forcing, but not loose. Apply on the whole a not greasy spray product to ease sliding. When no groove, you can fix a flat section strictly parallel to the blade, and slot the bottom of the sled, but that’s a very worst.

B - Baffled slider. This kind of slider is adjusted generally a little above the table of the machine, hence a risk of a light tipping you will have to prevent by gluing or screw small shims or plastic straps (Teflon) on.

C. - Level to the blade slider. It is the most reliable by its design.

Anyway, we must test first the sled is moving strictly in a parallel to the blade plane (otherwise the width of the saw kerf is not constant)

This sled receives a guide the direction of which is adjustable and is armed with one or better two spring clamps to support the board. Our fingers are precious, and better it is to avoid all the risks for the board to swivel when sawing.

Make with a router two reversed «T» through slots or embed and glue/screw extra flat curtain rail. This process needs a minimum thickness. The compromise not to loose too much sawing capability is around 20 mm, which ensures a correct stiffness. Think of 19 mm Bakelite plywood used as building formwork.

The guide will be about 40 cm long, and a lengthwise slot will be drilled. The link between the sled and the guide is ensured by two stove bolts and two wing nuts. Inserted washers will prevent the clamping to be disturbed.

A choice is necessary: must the guide be in front or behind the board? For me, the safety is putting it in the rear, to withstand the cutting force. It will have to be positioned at the closest to the blade. It will be broad and thick enough to receive two spring clamps to hold firm the board. Watch your fingers when only a few cm remain in the board!

It is better (see «triangulettes») to begin sawing by the great base of the segment, hence an angle adjustment at 90° - α and the layout of the figure 4.3.2. With experience (but it’s not compulsory), you will find a lot of good in keeping a little margin of the sled at the right of the blade, as drawn in the sketches below:

Fig. 4.3.2 (RM) Two samples of sled. The part at the right of the blade can be separated and fixed on the table of the machine, as the length stop in the drawing below.

When ending the sawing, you will observe that the blade is tending to catch the newly cut segment, which is dangerous and damaging to the segment. You will avoid this hitch by converting the right side into an inclined plane (see fig.4.3.1) as you can see on the photography below. (See also as an example the book of William Smith «Segmented Wood Turning» page 23):

Photo 4.3.3 (CG and FD)

To make the clearance inclined plane, the belt sander seems to be suitable.

We have to make now a stop system allowing at every sawing respecting the width B of the segment base. The wood is moving in regard to the blade, so this stop can be: - Either linked to the sled, and so we may draw an inspiration from the swiveling stop of the «triangoline type B» in the following chapter. The principal is for the segment to be strictly free when ending to saw. - Or linked to machine table and a magnet will do. We will adjust the position by taping with a small hammer. Potentially a "finger" in front allows avoiding the sled exceeding, if so. You will understand that, in the principle, the solution of the stop linked to the sled is better, for you will avoid the lack of precision caused by the sled shifting. And it is still better if the contact is in a line segment and not on an isolated point.

The sequence of the cutting operation by reversal on the sled is as follows: - unplug the machine - test that the blade is strictly perpendicular to the sled - work first on the waste block - adjust the spring clamps height adjust at the best the guide angle thanks to the bevel square (digital bevel square is better) and slide the guide as close as possible to the blade, for the board to be well held when sawing. - plug the machine in and cut the end

- turn the board over and adjust at best the stop at the distance B of the line of the blade (tooth protuberance). Measure with a calliper after sawing and correct B if needed. About this, turn the board over and work on the relative position of board/stop. The side of the board is used as a mark. Correcting a gap is better than doing again an absolute value measure. - cut N/4 waste segments and glue them. They must form a quadrant (three dimensional square). If the angle difference is less than 1° (between 89° and 91°), do not persist, it’s OK. Otherwise, start again. The adjustment of B would not change too much. If the angle is right, but not the diameter, make again the adjustment of B (rare case).

Back and forth motion and "triangoline A"

The reversal method is «not much flexible». The general direction of the board, the two edges of which must be strictly parallel, is necessarily perpendicular to the blade. We are winning very much flexibility, degrees of freedom; if we use an accessory I named «triangoline».

Its principle is very simple: using a double compass allows positioning the board. The first compass is a box swiveling around an axis linked to the sled. This not graduated «compass» gives to the board the general direction you desire. The pivot is as close as possible to the blade.

To this box a second graduated «compass» is linked, it allows the board to swivel of the vertex angle 2α by rotating either to the right, or to the left, and only with one adjustment that we find again from a segment to another one. The two compasses, or guides, have a common pivot fixed on the sled.

I used the two following tricks to make this tool. You can imagine other solutions. Here too, a detailed blueprint could not be in the scope of this manual. It would have little chance to suit all the machines.

1° - The positions of the back and forth motion are ascertained by a simple nail which runs with no loose through matching holes in the two guides. In the position «0» the guide 2 is in touch with the guide n° 1. The variable position «2α» is set after adjusting thanks to a holed bolt and its nut which run into a circular T slot made in the top cover of the guide 1. On this cover, the holding spring clamps are fixed, compulsory as for me.

2° - The usual reading of the angle on a protractor or a numerical bevel square becomes a reading of the corresponding arc of a circle. For that, the outward edge of the guide n°1 is cut into an arc of a circle centered on the pivot. To the length of the perimeter p = 2πr of this circle is corresponding a 360° angle, or N x 2α. On a glossy paper strip (or side covering paper of melamine table), you draw lines at the following distances: 0, p/8, p/12, p/16, p/24,…….p/48.

The more the guide is long, the more the arc is long and your angle setting is accurate. As an example, if the length of the guide measured from its rotation centre is 286 mm, a 5 mm gap on the strip is corresponding to a 1° degree angle, and it’s possible to estimate easily a variation of a tenth degree, which is not possible with a shop protractor. Imagine that for N20, a tenth degree mistake every cut becomes, when assembling the ring, it results in a gap of 20x2x1/10 = 4 degrees! The guide n°2 has an index-handle protruding over the guide n°1. You glue the paper strip on the vertical edge (side) of the guide n°1, while putting carefully the «0» of the strip upon the «0» of the index (guide n°2 laid flat against the guide n°1). And it’s as easy as ABC!

The pictures hereafter will permit for you to notice that all this process is not very complicate, either to understand, or to make.

Photo 4.3.4 The triangoline in sawing position The inverse T circular slot permits stiffening the direction of the guide n°1 thanks to a "stove" bolt and a wing nut. A second wing nut tightens the rotation axis of both guides. This layout gives efficiency to the spring clamp tightening.

Photo 4.3.5 The graduated side strip and the index handle allow adjusting directly the range of the guide n° 2 to the wanted angle 2α. N is limited here to 18, but you can go down to N8, provided that you indent the hood of the guide n°1 to tighten the board.

Photo 4.3.6 The guide 1 is dismantled. The guide 2 remains in place around its pivot.

Photo 4.3.7 The underside of the guide 1 The height of the guide 2 against which the board is leaning was chosen to face up to almost every situation.

Photo 4.3.8 Device allowing stiffening the setting the angle at 2α. The nail equipped with a knob runs through the bolt tightened over the guide n° 1 thanks to a nut (better than a wing nut to avoid an incorrect manipulation during the cutting operation) then the guiden°2. The drilled index «0» is well visible on the right of the nut, in the line with the groove.

Photo 4.3.9 Detail of the nut of the above device. A perfect centring of the axis hole is not necessary, the nut is fastened after setting, nail inserted.

What are the features in cutting with a triangoline ? First two examples of cutting sketches:

Figure 4.3.10 (RM)

1° Apart from taking up the «reversal» configuration again (two parallel edges at the distance of the width « l ») we get not finished regular trapezoids, but irregular trapezoids, or triangles, each one with an unchanging 2α vertex angle. In these triangles, trunconic or not, it will be possible to draw, and then cut both sides neglected by the method.

The cutting quality and preciseness are not very important, as regard the sides will be turned. Almost identical segments make easier however rings assembling. In spite of this additional cutting time, the whole execution time of a ring is not noticeable higher than the time necessary to reversal.

2° The back and forth motion allows to come back to the position «0» by cutting an upside down segment by the way. We may sum up by the following formula rotation + translation = segment, whatever the rotation direction can be.

3°The cutting sketch is free. You may choose as many start positions you want. You can so avoid the possible wood flaws (upper sketch)

4° The reversal is not necessary to use wood at the most (lower sketch).

5° No need to cut the board in its width. The triangles which can hold segments may be secant (sketch below).

6° The degrees of freedom in cutting allow, if we want, to orient the wood with the grain when turning, which is a pretty advantage.

The cutting operation sequence back and forth with a A triangoline is as follows:

- Shut down the machine - Check for the blade to be well perpendicular to the triangoline sled - First work the waste board - Set for the right spring clamps height - Set for the best the angle of the guide n° 2 thanks to the index - Set as you want the position of the guide n° 1 - Power on and cut an end. - Rotate the guide 2 and possibly make a sufficient translating movement of the board to reach the width B of the segment base - Separate a triangle out. - Make an inverse rotation over the guide 2 and if necessary a sufficient translating movement of the board to reach the width B of the segment base. - Start again the operation, and change if necessary the position of the guide N°1 until N/4 segments. - Cut the surplus of the triangles after marking. - Glue the waste segments. They must form a quadrant (three dimensional square). If the angle difference is less than 1° (between 89° an 91°) do not persist. Otherwise, make again the setting of the guide 2.

It is advisable to add that the use of the triangoline does not forbid in the least the reversal method, quite the reverse! It makes easier indeed the angle setting. The principal is that we must not forget we have to adjust the angle at 2 α and not α, so the mark must be on N/2 instead of N.

In conclusion, it is obvious that only your own experience of the two processes, if making a triangoline does not discourage you, will allow you to choose, according to the events and the woods at your disposal, between reversal and back and forth.

4.4 Trapezoidal segment with miter saw

Almost everything we have just examined as regards the stationary circular saw can be applied on miter saw (or compound miter saw).

There are however basic differences as regards technological characteristics of the miter saw:

- The blade is moving toward the wood, as well in down motion as in carriage motion. - The blade can turn around a vertical axis when the wood remains fixed - The blade is tilting like on the stationary circular saw (with furthermore the possibility of tilting to the left), but it is linked with the engine block and so the assembly is very less steady. - The translating movement, or carriage motion, is not as precise as on a circular saw - The sawing operation produces much dust - The adjustments are made near the blade and against the blade, and you must shut down systematically. Insert a warning light switch on the power cord, well visible from the work area.

Those differences may be either advantages, or inconvenience. Don’t rush to choose one or other saw. You will be glad perhaps to keep the availability of the circular saw while the miter saw is assigned to segments cutting. You will like also to work at the standing height you will have chosen on the miter saw...

Let us kill immediately the genuine instability of the tilting block. On every machine I examined, the tilting jamming is made by tightening on the back of the engine block, with a light lever arm or on the rotation axis itself. It is not sufficient for the unusual purpose of such a saw.

Not many machines are similar to the above one, but I suggest a device which could be fitted with most of them. The point is to link the engine block to the swivelling stand with a threaded rod, this rod sloping as little as possible. So we kill two birds with one stone: the wanted stabilization and a micrometrical setting with two wing nuts.

Given the lack of reliability of the carriage motion, which involves flatness flaws of the cutting plane, it can be at least partly circumvented while ...avoiding this motion; diving the engine block is indeed sufficient most of the time to operate a full cutting of the board. The cutting start must however remain frontal.

Here is the stabilization and micrometrical setting device I imaged for my own machine. It can be adapted to many other miter saws.

Photo 4.4.1 Overview of the stabilization device: upper anchorage by hinge on the engine block, 8 mm threaded rod sliding in the lower anchorage pivot, Linking bar (aluminium, rigid) with the swivelling stand.

Photos 4.4.2 et 4.4.3 Details of the upper and lower anchorages

Now the dust remains, much more bothering than with a circular saw. It is advisable, and even necessary to link permanently the machine with an automatically starting vac. And if possible adjoin a workshop vac!

The reversal

Theoretically, you can do without a sled; the rotation of the board to the wanted angle α can be made by the machine rotation, however, provided that the back guide is rigid and well rectilinear. You can improve the process and imagine a micrometrical adjustment of the rotation angle (which does not concern necessarily very great angles; see the tables in the chapter 3).

You have then only to → find a support device of the board during cutting. According to the literature, some people work with their fingers, or look for help from a kind of a hand held hook. I don’t rely on this method and I prefer the «spring clamp» or something similar. → fit a reliable and convenient stop of an adjustable length. Under these conditions, the sequence of the cutting operation is more or less the same as with the circular saw, and I’ll no more write back to it.

I think nevertheless that you will be tempted to make a triangoline fitted to your miter saw, the triangoline B, as good for the back and forth as for the reversal.

The Back and forth move and the "triangoline B"

The principle of this tool is exactly the same as the circular saw triangoline one: a double «compass» directing the board. However, there is a considerable simplifying; the compass inserted straightaway into the machine allows operating the general orientation of the board by rotation of the engine-blade block.

So it is enough to add the «compass», or adjustable guide allowing the back and forth motions at 2α angle.

We will build a sled to house this adjustable guide and the length stop, not forgetting the board supporting spring clamps and an easy angle adjusting.

See below the pictures of the triangoline B I made, after two preliminary works, on the base of simple sketches of operating principle, on tracing paper, for visualising the relative motions of the different parts. I did not make a blueprint, for lack of universality.

We find again the already described tricks used for triangoline A. The main difference: the sled is divided into two parts. → the right part is linked to the rotating block and receives the toppling length stop. → the left part is linked to the framework and receives the «compass», or adjustable rotating guide.

Photo 4.4.4 Overview of the miter saw with its triangoline B

Photo 4.4.5 The «compass» forming the left part of sled. Two concentric grooves are necessary. The first one, a reversed T, allows the positioning of the pierced bolt used as angle mark, as the one of the triangoline A. The second one permits the clearance of a bolt anchored on the sled, operating the locking of the guide (rotating part) which suffers in particular the vertical stress of the spring clamp. The wing bolts are profitably replaced by thrown off toppling clamping bolts

Photo 4.4.6 A graduated strip glued on the edge of the compass-guide permits the adjustment of the vertex segment angle by reading directly the number N (a ring). Matching the mark N of the guide with the mark «0» of the supporting sled, cut as per the same arc of the circle (with the router), is sufficient.

Photos 4.4.7 and 4.4.8 (RM)

The two positions of the Plexiglas tilting stop. The open position frees the segment as well when starting as at the end of cutting. The base is made of 30 mm medium. It's clearing groove allows the passing of two clamping bolts (one should not be sufficient). Two or three reversed T grooves oriented along the blade axis, are hollowed out on the right sled, attached to the rotating part of the machine, which permits to place the stop stand in the good position.

Cutting operations sequence with a triangoline B.

If «guide n°1 rotation» takes the place of «engine-block rotation» and «guide n°2 rotation» takes the place of «guide rotation», the sequence of back and forth cutting operation with a miter saw is the same as with a circular saw, which is advisable to refer to.

As for the sequence of the reversal cutting operation with a triangoline of the kind B, it is the following one:

- Shut down the machine (indicator lamp off) - Check the blade is right vertical, perpendicular to the left table of the triangoline and put the rotation in the position «0» - Begin working on the waste board - Set the spring clamps height - Lock the guide in the position «2 N» (angle α and not 2 α) - Power on and cut an end - Turn the board over and adjust at best the stop at the distance B of the right of the blade (edge of a tooth). Measure with a calliper after sawing and correct B if necessary. For this purpose, turn the board over and act on the relative position board/stop. The side of the immobilized board is used as mark. Correcting a gap is easier than making again an absolute measure. - Cut N/4 waste segments and glue them. They must form a quadrant (three dimensional square). If the angle gap is less than 1° (between 89° and 91°) do not insist. Otherwise, begin again. The adjustment of B should not be altered too much.

If the angle is correct, but not the diameter, make again the B adjustment (very rare case)

4.5 «Pyramidal» segment

Is the pyramidal process harder than the trapezoidal one? The answer is yes, three times yes. The adjustments are more numerous, and request still more attention and preciseness. Let us go through the different parameters.

The layer height is no more the same as the board thickness. It is the outcome of the combination between the splay angle «i» and the board width. The size B becomes the size of the bigger width on the larger base. It can be measured only on a segment edge.

The angle α is now only an auxiliary parameter, dependant on N, which appears in calculations, but with no application on the machine. Two angles β and γ take its place (or φ instead of γ). These angles must be kept scrupulously to get the hoped pyramid trunk with N sides in a ring, defined by its height and its higher and lower diameters.

Before hurrying into machining of a ring segments, or a pyramidal trunk, testing your machine, either stationary or radial, is the first thing to do to know whether it suits this kind of work.

In order to appreciate whether it is «right», as told, make a lightly slanting cut (a great tilting is of no use in the pyramidal process; see the angle γ in the table 3.4.4; as soon as N is more than 12, γ is less than 15°) in a board of a 35 x 180 mm about section. Turn over the two sides ensuing from this cut and put them one against the other both pieces not in the continuation of one another. The two sides must fit on one another with a minimum of flatness flaws. A gluing test is very informative. When rubbing one side over the other, the glue must flow back everywhere in the same manner.

If your machine suits well, go on.

Examine the details of the cutting, and chiefly at sawing end. You must have only minimal pulling off. The flaw may come from a wrong sharpening of the blade, and this occurs even with new blades.

Theoretically, you have four opportunities to make pyramidal segments in accordance with the instructions in the chapter 3.4 concerning the sketch drawing and the calculation of the segments parameters. Doubling the choice between circular saw and miter saw by back and forth and reversal processes gives in fact these four opportunities.

However, we have to acknowledge as we go into the details, the reversal is not suitable for pyramidal segments. The explanation lies in the need to have perfectly identical segments to make easier the assembling and the intermediate turning.

So I’ll confine my talk to the reversal method.

The blade incline on most of the stationary circular saws is limited on the right, when it can be in both directions on miter saw. So the following six manners (instead of eight) remain to insert the board according to this tilting (that is to say the tilting of this kind of saw) and the choice of the acute or obtuse angle made by the guide with the blade:

Fig. 4.5.1

The six conceivable patterns. The better one is F. The saw blade appears as a red continuous line

In essence, the cut board is slanting. This makes still more dangerous the use of a usual length stop (diagram A) than in the case of the trapezoidal segment. The support comes down to one point and not to an (vertical) edge. The «point» is easily damaged, or it is crushed when it comes to a stop. So, we are brought to use either a stop cut out from a first off cut of the waste board, after the first adjustment of the angles (diagram C), or a pivoting stop, drawn on the diagrams D and F.I have chosen the pivoting stop, and this is what I suggest.

But the segments radiating sides are cut in a full section, and the edges they form with the lower and upper sides of the board are sharp. This sharp «dihedron», if in a lower position, runs the risk of sliding under the stop shaft, which makes inoperative the adjustment, as in the case A, B, C and D in the figure

In the cases E and F, the blade is slanting to the left, and the stop can fit efficiently. So, if we have choice, better it is to forget most of the stationary circular saws in machining trapezoidal segments in the conditions I think the best ones.

Besides, there is an indubitable advantage in sawing the segments by ending by the tip, that is to say the small base. It is obvious in the case of the triangulettes, in which this small base is reduced to an edge (see next chapter). We get rid so of the positions B, C, E.

In the end, when matching all these observations, we are brought naturally to prefer the pattern F in which, moreover, the pivoting stop moves apart the saw blade in an open position (which would not be the case in the configuration E). This configuration is thus written:

Miter saw blade slanting to the left + reversal + pivoting stop + acute angle between guide and blade

We saw in the previous chapter that the difference between circular saw and miter saw as regards trapezoidal segments cutting is reduced to insignificant thing. It will not be difficult for you to adapt the first one, what suits to the second one as regards pyramidal segments. If the blade of your stationary saw cannot slant to the left, I believe the best configuration is the following one:

Stationary circular saw blade slanting to the left + reversal process + slanting continuous stop (as in the diagram C) + acute angle between guide and blade.

I point out that preference does not mean elimination, the configuration F, to the credit of the miter saw, will be kept in the continuation of this chapter, what has the advantage not to make heavy useless explanations. Using a triangoline B is extremely recommended, even if it would be only to allow the installation of an adjustable stop, swivelling or not.

We shall now examine one after the other the different operations which will allow reaching the overall sought result: a well regular ring, inserted with no problem into the general shape of the piece sketch. A pretty challenge!

1° Like in the case of trapezoidal, we cut well planed boards (thickness measured with a calliper in several places), in a constant rectangular section, with straight and parallel edges, a waste board and a final board. Don’t neglect this operation the continuation of which is depending on, and it will be really so with the successive operations. The last putting up disc sanding process is only a last resort.

I think it is necessary cutting the sides (lengthwise, of course) at the splay angle «i», and letting a small 1 or 2 mm margin (chamfer), as you can see on the sketch 4.1.15.

It is essential in order to check the assembling and make easier the primary turning of the ring, before including it into the sketch of the piece. A cutting with no residual

84 margin is not possible to make, except if we give up having well straight and parallel lengthwise edges. In this operation, the board section symmetry must be kept. I think using a circular saw is well fitting, and the following picture requires one comment only: don’t tamper with the guide between the two cuttings, for it will ruin the symmetry of both edges. Think to stop up the blade residual slot on the left side with a sticky tape to prevent jamming the triangular scrap at the end of cutting.

Photo 4.5.2 Cutting of the edges of the board according to the « i » splay angle.

Now both boards are ready, and we may begin radial sawing, the first one to be worked is of course the waste board.

2° Shut down (remind: very useful and essential warning lamp)

3° Adjust « smoothly» the holding spring clamps height, with no excessive effort on the guide

4° Lock the engine block rotation (theoretically on the zero), then adjust the triangoline guide rotation.

For this purpose, pull the blade down; lock it with the carriage cotter. Lean the blade to the left in a position near 90° - γ (the preciseness in not necessary at this stage of the sequence).

Once again, check the warning lamp is off. Find the means (variable from a machine to another one) to lock in open position the safety shielding cover. So the blade is cleared and pulled down.

Adjust the guide/blade angle according to the acute angle 90° - β with a digital bevel square well flatly placed over the left sled. The simple transfer from the sketch with a «traditional» bevel square, even with a heel, is doomed to fail because of lack of preciseness.

Lock the index bolt, nail inserted. Lock both swivelling bolts which link the guide to the sled. Now the guide is wedged on rotation.

5° Raise the blade, still locked cover. Adjust precisely its tilt at the acute angle 90° - γ with the digital bevel square, which must stick against the guide and remain in a vertical plane, perpendicular to the plane of the sled. I have by far this tilting adjustment from γ rather than from φ because of giving rise to additional errors, and we have ones still enough! (If you make an adjustment from 90° - φ, you must find the position of the bevel square when its plane is in the same time perpendicular to the table and perpendicular to the blade). On the other hand, the choice of the angle γ makes necessary an adjustment of the rotation before the one of the incline.

In order to make cosily this adjustment, a magnetized rest such as the one of the following picture will be very useful to you.

Photo 4.5.3 Wooden rest of digital bevel square. A magnet stuck glued in front holds firm the vertical leg of the square.

You will like also the opportunity of a micrometric adjustment thanks to the stabilization threaded rod. Don’t forget fastening both wing nuts after adjusting, and the original rear pivot.

Photo 4.5.4 Overview of the (compound) miter saw under adjusting the 90° - γ splay angle.

6° Free the safety cover and power on.

7° Cut the end of the test board. Before every cut, lock the holding spring clamps, then release them.

8° Shut down again. Turn over the board; draw the second radiating edge of the segment as precisely as possible. Slide the board against the guide until a right angle of the blade tooth (lowered, raised cover to see well) line up with this drawing as on the below sketch:

Fig. 4.5.5 Adjustment of the size of the base B. The saw blade is depicted with the juts of its tooth(dent). The swivelling leg of the stop is in closed position. It must be open before sawing. In the pattern F of the figure 4.5.1, the big side of the segment is on top and the big base of the segment in front, which makes much easier the adjustment of the dimension B.

Lock the board with the spring clamps. Bring the swivelling stop (closed position) against the first edge of the segment. Lock the stop position on the sled and swivel it open. The test adjustment of the width B comes to an end.

9° Saw the first test segment. Test the value of B with a vernier calliper. In the case of a difference, make again the adjustment of the stop. If B is too small: turn the board over, bring it as a stop and lock it. Release the stop and move it to the right from the value of the noticed difference, while keeping the parallelism with the edge of the segment. Lock the stop and make a new cut of the segment.

If B is too big, make the reversed operation, move first the board. Make again a cut of the segment and test. Theoretically, the sought result is got after this second approach, and then we shall not write again about B, the adjustment of which is definitive.

10° Cut N/4 segments. Arrange them flatly on their big side. The combination placed flatly side to side must form a vertex angle (lower than 90°) very precisely equal to

N/4 x 2 β° or N/2 x β°

Make this multiplication, then draw an angle of the same value (with a digital bevel square) on a flat material as well as arcs of the circle to make easier checking. Arrange N/4 segments inside this drawing, with the help of a double face tape if needed to hold them steady.

Variant: measure directly the angle while pressing (as better as possible) the legs of the square on the edges of the farthest segments of the tested group. But the comparison with the drawing on the material is better. The edges of the farthest segments must fit to the drawing at a 1° or 2° angle. Otherwise, start again by adding or subtracting a new adjustment of the rotation to the 90° - β angle and begin again the operation. Here a micrometric adjustment is welcome. You have to find the solution fitting to your machine... and your inventiveness.

Photo 4.5.6 The combination of N segments in a pyramidal layer placed flatly side to side forms an angle in the center smaller than 360°.

A direct presentation of a construction glued in a shape of a quarter of pyramid on the three dimensional square would not make possible for you to know, in case of an error, whether it comes from the rotation or tilting adjustment, hence this two times checking.

11° The 10° above operation being completed, glue the N/4 segments, need be in a few steps if there are more than 2 ones (see chapter 6.2). This gluing can be made in a few minutes, if you use fast drying glue. Show the arrangement on the three dimensional square.

Either the error (now limited to the tilting, by a process of elimination) is acceptable and can be salvaged by processing with a lapidary sander, and we can start cutting the final board, or we have to begin again the tilt adjustment, according to the angle 90° - γ, I remind you.

Don’t skimp on all these operations. We have to reach, right from the sawing of the segments, to an acceptable assembly requiring only small corrections with the disc sander on glued pyramidal trunk quarters. Rework one by one with the disc sander every segment before gluing causes nothing good. We believe saving time… and we lose much of it!

12° Go now to the sawing of the definitive segments, and number each one on the big side (outside face when assembling), in order to find again the so useful continuity of the veining and the colours of the wood, and well make the ring quarters out when we will work them with the disc sander before the last gluing stage.

I remind you finely a basic precaution : make all the adjustments power off!!!

4.6 Specific segments and "triangulettes"

In order to colour better the language, I used the words «trapezoidal segment» and «pyramidal segment». The first one is trapezoidal only when we look at it from on top. In cross-view, it is rectangular. Anyway, it is radiating… The second one is pyramidal only because it takes part in making up the hollowed trunk of a pyramid, as it is trapezoidal seen from top, and its vertical section forms a parallelogram!

We must be aware it does not make easier the work to give a name to the two other segments we can carry out thanks to the tilting of the blade and the back and forth method. The coming of the triangoline I imagined explains probably this little word difficulty. Without the triangoline, which allows the back and forth method, the problem would perhaps not be raised.

The five kinds of «tangential sections» (or vertical and perpendicular to the median radius) of radiating segments are the following ones, the big side being in front of the picture.

Fig. 4.6.1 The tangential sections of the segments the radiating sides of which are flat

A is the rectangular section in the «trapezoidal»

B and C are the trapezoidal sections in the «pyramidal». The section C is nothing other than the reversed B and vice versa. In fact, these segments are genuinely pyramidal only when the value of the splay angle «j» of the side faces is equivalent to one of the discrete values (discontinuous value) of the angle γ in the table 3.4.4 (Otherwise the ring cannot be closed).

D will be the one, in a parallelogram, of the «diagonal on the right», blade tilting on the right. E the one, in a parallelogram also, of the «diagonal on the left», blade tilting on the left. D and E are properly realizable in series only by the back and forth method, so with a triangoline. Turn over from 180°, you will see they are not identical. E is properly realizable only with a miter saw equipped with triangoline.

All those segments are trapezoidal seen from top, and triangular when the dimension of the small side becomes null. Hence, we shall name them "triangulettes". Placing them side to side and gluing fitting triangulettes makes a disc.

Photo 4.6.2 Sample of N 40 ring with D and E triangulettes. Ebony and maple. See the front cover picture

To make open layers, every segment or triangulettes from A to E can be combined, and it allows aesthetic fantasies as in the below piece, which presents slots tilting alternately on the right and on the left:

Picture 4.6.3 Open box in closed shape; palissander and wild cherry

Photos 4.6.4 et 4.6.5 Open composite disc assemblage. Solid N 8 rest disc. Alternated pyramidal triangulettes, on top, underneath. Trunconic cutting is made with a band saw. Impossible with "triangoline".These layers will be included into the above piece 4.6.3

Making solid layers, in other words solid rings (oh what a pleonasm!) or full discs the following combinations, which offer enticing prospects, are possible (see above picture 4.6.1):

AAAA… BCBC… BCDBCD… BEBE… BECBEC… DDDD… EEEE… Pick from this battery, you will have stuff enough!

Openwork design with triangulettes

Openwork design is an important part of layered turning.

There is an original manner making single open layers, from simple triangulettes, with radiating flat sides, but also with "curved triangulettes" (by extension of the word), generally triangle shaped, but the radiating sides of which are not straight.

Here are samples (figure 4.6.6.) of such triangulettes, which, almost all of them are «fitting into one another», this means that the cutting of one of their both radiating sides is identical to the cutting of the next one, which makes the work easier. The pointed end is knowingly in the center of the layer. Nevertheless it is not necessary for the triangulettes to be «fitting into one another» to make an open layer.

In the below samples, F and H, the central pointed end of which is turning to the right, must be reversed one time among two when assembling. I is not fitting (stackable).

For a triangulette to be «stackable», its edge outline must have a tangential axis of symmetry. The flat view of the triangulette is given by taking a fair copy of the same outline and rotating it of the wanted angle around the top, center of the piece. If you want to draw an edge and check the drawing is fitting, use a tracing paper.

The openwork design allows freeing from a great preciseness when cutting, with a band saw or a scroll saw. Small defects cannot be evaluated. The «radiating» vertical sides are naturally sanded before assembling.

The concave sides are sanded with a vertical sanding roll on table, of an appropriate radius, lightly shorter than the curvature radius of the triangulette. If you work with a spindle moulding machine, watch that it is «slow» speeded, 3000 turns a minute about; otherwise you will get almost surely wood burns. The best is a vertical oscillating roll.

With the convex sides, work rather with a band sander (vertical or horizontal stationary position) or with a disc sander. K has straight parts, and will be more difficult to machine than G.

The rectilinear recessed parts of J are not very easy to sand, except with a vertical band sander.

Fig. 4.6.6 Some samples of curved triangulettes, every one fitting into each other except "I".

Photo 4.6.7 Drawing of «stackable» curved triangulettes, with a cardboard template. The process is wood… and gesture saving

Photo 4.6.8 Sample of an assemblage of curved triangulettes making an open layer. Machiningthe central empty space on a lathe with a wood bit. A trunnion will fill this empty space and operate a good linkage with the other parts of the piece. Here we see the lid of a box that will receive a finial.

Gluing tiangulettes into discs shows a particularity: the pointed ends, when N is great, then α is small, tend unpleasantly to stick up (become horn shaped) from the combined effects of the release of the inner constraints of the wood ensuing from sawing, and the drying favoured by this sawing, and chiefly from the effects of glue soaking before it dries.

So it is advisable to choose thinly grained woods, with a well stabilized hygrometry. Moreover, you must provide a sufficient number of "stringeons" with a small gap between the tips to pinch the pointed ends with each other when gluing. Fortunately, the putting out of shape of a pointed end is often at the opposite of the next one.

I thought interesting to draw up the following table of the required equipments to work with the triangulettes. Besides the five first columns of this table apply to the straight sides radiating segments. The letter X means the machine is absolutely necessary if you want to remain self- sufficient. The letter Y means a variant is allowed in the column in consideration. The references of the columns A to E are the marks in the figure 4.6.1; the references in the columns F to K are the marks in the figure 4.6.6.

"triangulette" kind Tooling, machines A B C D E F G H I J K Thicknesser-planer X X X X X X X X X X X

Circular saw Y Y Y

Circular saw + triangoline Y Y Y Y

Miter saw + triangoline Y Y Y Y Y

Band saw or scroll saw X X X X X X

Vertical roll sander X X X X X X

Disc sander Y Y Y Y

Vertical belt sander Y Y Y Y X X

4.7 Composite segment

The segment is named «composite» when it is made of several kinds of woods, or in a special drawing ensuing from the combination between different veinings of the same wood. Identical to itself, it can be found all around the circumference of a ring. It can be made alternately of one wood segments, small boards, veneer leaves. It can be trapezoidal or pyramidal.

Every composite segment of a ring may be single, and make up in itself a genuine miniature art work. In short, we open here to many possible combinations and aesthetic researches.

I shall content myself of general remarks, without interring into the detail of machining of composites segments, as different and complex as your know-how and your imagination allows it. The whole of it is maybe countable, but endless!

As regards the greatest part of the composite segments adorned pieces, I’ll begin by trapezoidal segments rings. If you desire to launch into this work, you must know that there are two manners to insert composite segments into a crown, which are seen on top in the hereafter sketch.

Fig. 4.7.1 Both inserting manners of a composite segment (letter C) into a crown, either between trapezoidal segments (letter T), or between small boards (letter P) On the left, the composite segment is rectangular shaped, which can «make the life easier», in a few cases. Usual trapezoidal segments (letter T) make possible to close a ring, according to the geometrical conditions examined in the chapter 3.2 (figure 3.2.9). On the right, the composite segments follow one after another, alternately or not, with a small board or a veneer leaf (letter P). Actually, as regards the definition, the addition C + P makes up already a composite segment, even if C is a single wood segment.

Here, as an example, a first kind piece (rectangular composite segment), where the veining of the zebrano is simply highlighted, but outstandingly.

Photo 4.7.2 (GB).

The perspective sketch explaining the method chosen by Gérard Bidou, author of this piece, permits for you to foresee a very little part of the research field that lies ahead in front of you, even if you limit yourselves to the rectangular composite segment.

Fig. 4.7.3 (GB)

You will find another sample of composite segments, making a Greek frieze, in the chapter 8.5 dedicated to the «Meandros» bowl.

The rectangular segment is very practical, for it allows to be reproduced while simply dividing a collage of square lumps, small boards, etc. Nevertheless, most of time, it brings to turning end gain, and does not allow al the fantasies of the composite trapezoidal made piece after piece from wood small boards.

Let us now double the difficulty, and make the segments one after one, from boards, those segments being in the end changed into trapezoidal ones. You must then summon up much of your patience, take a good disc sander and a good aspiration around this dust throwing up machine. The work consists successively in gluing and planning down previously rectangular small boards.

Hereunder, there are samples of front view geometrical patterns the combination of which gives stunningly beautiful pieces, as the Ray Allen’s ones. His overabundant and wonderful creations spread over a dozen of years, from 1988 to 2000, the year of his death (see chapter 9).

Fig. 4.7.4 Samples of composite segments

At the left top, the zigzag, a «classic» one, produced by many artist wood turners.

At the right top, the «wedge» which allows many variants.

At the left bottom, the «diamond», the characteristic of which is being greedy for wood and dust prolific. We start from rectangular board we trim and trim to the suitable angles, with the disc sander, before and after gluing every segment in between four times. At the end, about a only quarter of the wood of the initial boards remains! At the right bottom, a «Greek» among about tens of others. (Note this segment can be made also from triangulettes).

The circular saw

The outstanding turners the books of whom I consulted, who yet display otherwise a wonderful cleverness, don’t burden themselves of precautions and take great liberties with the safety of their fingers, keeping very small wood lumps from the circular saw blade, either stationary or miter saws. You will be enlightened by seeing the picture of the «back cover» and the number 57 in the page 32 of the book of Dale Nish on Ray Allen, or the picture of William Smith page 23 of his book «Segmented Wood Turning» or still the one on the top of the page 78 of the book of Malcom Tibetts «The Art of Segmented Wood Turning»!!

You have understood: the difficulty, once basic gluing made, lies in making two radiating cuttings of each segment, if you prefer to avoid using disc sander (see further in this chapter). There is a solution, reliable on safety and reliable on preciseness.

If we join segments several times end to end, as we explained above, the combination of the sketches of the segments in a ring becomes a strip we can work either by the reversal, or the back and forth methods. Gluing is made by leaning against two orthogonal straight guides making an extended T square. 98

We still improve the trick by gluing on both sides of the strip of the sketches a support and alignment board the height of which is the same as the segments one (just as thick as each other to keep to the symmetry), while inserting a paper leaf, for the parting between board scraps and segments be easy. Note that, if we resort to the back and forth method, an alignment board is sufficient, the symmetry being not essential.

Knowingly, the saw guide is first adjusted at the right angle, and checking was made on a waste board; likewise, the length stop was suitably adjusted, taking notice the alignment boards are in place. Here underneath, the explanatory sketch:

Fig. 4.7.5 Cutting of composite segments joined together

This method allows in the same time protecting one’s fingers, respecting and evening the base broadness of the segments and making sure of a right angle cutting. The disc sander comes very few only at a time when assembling the ring.

The only little drawback is the over broadness to anticipate the two saw kerfs at the sides of a segment. You must pay attention in this sample at the time of the first skew cutting, to every strip shift, for the pattern to remain in the center of the rectangle ensuing from the cutting.

The disc sander and the "triangoline C "

Let us leave the saw, yet so attractive, and come into play with the turners who worked wonders using almost solely the disc sander. The tool they use to give the right angle to the segment, individually machined, is simple. You will find the theory in the following figure:

Fig. 4.7.6 "Classic" disc sander jig

A sled slides on the table, in parallel to the plate, which allows changing the working area of the abrasive plate and trimming the sanding. The guide G1 is set at the sled, perpendicular to the plate. The guide G2 is adjustable along G1, but wedged after adjusting the wanted width of the segment.

Its end cutting at the angle 90° - 2 α forces the segment after sanding to keep the vertex angle 2 α.

The drawback is we must make a new guide G2 every time we change the number N of segments in a ring, that is to say the angle α. The story does not tell how with such an accessory the right angles between the bases and the sides are secured.

That’s why I imagined a more complete accessory I named «triangoline de type C» (triangoline of the kind C) which has two «compasses» as the two triangoline A and B (hence its name).

Find below a sketch as an example:

100

Fig. 4.7.7 «Triangoline type C» (triangoline of the kind C) Example of schematic blueprint

The running is the following one: The guide G1 turns around a fixed point connected to the sled which slides in a parallel to the disc. After adjusting at the angle 90° - α, G1 is wedged in regard to the sled. The guide G2 slides freely along G1.

The G2 includes: → a ruler G 2.1 which fits into a G1 rabbet and will be used as a support to a base of the segment (T) → a second ruler G 2.2 which swivels around a point sliding along the first ruler. This G 2.2 ruler makes an angle 2 α with the sanding disc. → a crosspiece G 2.3 wedging G 2.2 after adjusting its position and its angle; → an adjustable stop allowing limiting the base width of the segment T to the wanted value B; → we can think of screw micrometric adjustable devices as well in regard of the angles as of the length stop.

We start from this fairly adjusted set, as previously, with successive approaches. A trapezoid T, the radiating cuts of which are imperfect and the length B greater than the definitive one, is inserted between the guide G 2 and its smaller base is firmly held against the support ruler G 2.1. While sliding G 2 over G 1, a first radiating side is set at the wanted angle.

Note the sanding is made by bringing closer to the disc the set G2 + T.

101

So, we will take care in the same time to spare the disc and make the sanding at the best, to make back and forth motions with the set supported on the sled, before coming to the stop. We stop when one side of the segment is set, while keeping wood enough for the other side.

We turn then the segment over, and we begin the operation for the second radiating side. It’s finished. To the next one! I made this device, following (almost) the above drawing and I can tell you it works!! The triangoline C is awesomely efficient, as well speedy as in regard of the respect of the angles and the width of the segment base, thanks to the adjustable stop.

A few pictures are best than a long speech:

Photo. 4.7.8 Triangoline C. Overview Assembling units and adjusting the length stop by stove bolts and wing nuts

Photo. 4.7.9 Triangoline type C. A segment ready to machining

102

Photo. 4.7.10 Triangoline C. Front view. Thanks to two cleats, the sled covers the disc sander table (30 mm medium) the edges of which were sawed well in a parallel. The bakelite plywood slides perfectly over the medium.

Photo. 4.7.11 Triangoline C. Details of the length stop. Nothing’s simpler! A micrometric adjustment is thinkable, with no great imagination effort.

103

Photo. 4.7.12 Triangoline C. A small style exercise with the moulding machine for inserted runners. Router working for curved cutting and opening. No angle reading, but marks according to N (here adjustment of 24 segments in a ring)

Intarsia and other curved fancies

Till now, we were «satisfied» with composite segments having only in themselves flat sides. It is possible to insert curved faces by working with a scroll saw, and … even with a lathe, our favourite mate.

I think very important a detail I have not yet mentioned. To preserve the chosen drawing, the «composite» layers are put in a prominent position into the parts of the turned piece where the splay angle is small, that is to say, the «vertical» parts where the necessary raw thickness is the weakest. Moreover, from N = 12, the tangential loss of wood when turning is weak. When those two favourable elements are added, we can work weak raw thickness, about 15 mm and even less. So, we can make high enough as well as little thick segments. You’re free to choose your way of radiating cutting that suits better, flat position (like for pyramidal segments, with β = 0), or vertical line of the board.

Thanks to this weak thickness, it is possible to resort to the «intarsia» to make friezes the drawing of which is theoretically very free, by cutting with a scroll saw 2 boards one on top of the other of different woods. Try first in order to know the limits of your saw... and your blades. Here, basically, what can be got after having jointed the wood N. 1 into the N. 2 one.

104

Fig. 4.7.13 The composite segment at intarsia

Starting from one of these friezes, we can add a third kind of wood, a complementary outline of the first one, and get a still more complicated drawing. It’s possible also to cut such a frieze in its length…in short, the process is prolific. The perfect fitting of the cuttings is not much possible. It is so recommended cutting with a slight gap in the squaring of the table in regard to the blade, and make later slide the two pieces of the frieze for them to joint perfectly. Moreover, because of the width of vertical saw kerfs, the perfect continuity of the profile is not secured. A small bit is missing every time we go over from a segment to the next one.

You will have to correct this disadvantage by putting an intermediate board between the composite segments or drawing a profile lightly curved and slightly sloping at every passage of segment. The notice is valid surely when closing the circumference and you must absolutely draw the whole of the frieze before beginning cutting. Don’t forget a small margin between the segments for the saw kerfs and for a few fitting over our dear disc sander.

We must stress that, knowingly, the inner drawing is different from the outside one. The segment is shortened in its width, but not its height. Better it is so, to use intarsia only for the closed pieces, when the inside is not visible.

The lathe can also be the source of composite segments with curved inner sides, by cutting glued and turned elements. Here is a sample:

Fig. 4.7.14 A composite segment made at the lathe. We make a disc from 16 "triangulettes".The disc of which 2 composite segments only remain after trimming! Patience… Most surprising: some made it!

We have here the opportunity to re-examine what’s preceding in regard with the triangulettes.

105

We start from 16 triangulettes cut into different woods. We put them together by the pointed end and we glue them on a disc (plywood, high-density wood, etc) fixed on a small paper covered plank, centered with a pencil on the lathe. The central hole is made thanks to the lathe, the bit pushed by the headstock. It is filled with a trunnion turned on demand. (Hence the interest of the plank allowing dismantling between both operations). The set is flattened on the lathe, then separated from the disc with a simple kitchen knife, then and AT LAST parted in two along a diameter.

If the thickness is twice that of the segments to be, we cut again in two and we get so 4 composite segments from only one turned assemblage. But fitting and gluing a trunnion into a hole is not easy, and so the assemblage thickness is limited.

The pyramidal process

We met already, in our introduction, a pyramidal turned piece made only of composite segments, strictly speaking. Look back to the picture 4.1.13. The aesthetics of that piece is ensuing only from making use of the reversal method.

The opportunities of the «pyramidal composite method» don’t stop here. Actually, in practice, everything was written as regards the trapezoidal method is adaptable, and this will improve the «composite» in its whole. It’s possible to put forward two main contributions: → the opportunity of increasing the splay angle with a very small distortion of the drawings making the final aesthetics of the piece. → a noticeable increasing of the layer height. And now, on with the dream...!

106

5. Making rings from discs

5.1 How assembly the discs in order to cut them

The simple segments’ assembling is the most frequent approach of the layered turning. It’s surely because it allows all the fancy compositions.

Stacking up full or open layers ensuing from discs cut in rings is another a little less «flexible» way of making, but overall quicker and more reliable. “Quicker” because the rings ensuing from discs are in a way «fore-assembled». “Reliable” because their closing gluing raises no problem when the discs are well prepared.

We shall address in the next chapter to the different cutting ways, which generate some constraints on which the choice of the disc depends. For the time being, we shall be satisfied with preparing those discs, from assemblages roughly in the form of squares, hexagons, octagons or... circles.

Find below sketches of discs arrangements, everyone made from what we know making easily by machining well planed boards, of same thickness, into woods of different tones and veining: → boards with parallel or not edges → triangulettes or trapezoidal segments

Fig. 5.1.1

107

Assembly n° 1

The edges of the boards forming the disc are not parallel. As regards the technique, this allows using the «leftovers» of high grade woods with not much waste. The same process anyway is used by the joiners to make the solid wood door boards. When turning, we meet much wood with or against the grain. The aesthetics comes from alternating woods with strong contrast, and a series of segments the shapes and dimensions of which (apart from the height of course) vary systemically. See below a disc of this kind:

Photo 5.1.2

And the piece made from this disc in which no segment is identical to another:

Picture 5.1.3 «Scottish bowl»

108

Assembly n° 2

This gluing is only a variant of the number 1. I think it offers no interest, except when saving already ripped woods as floorboards.

Assembly n° 3

The assembling on the picture is deliberately reversed as regards the usual turning direction. It will be put back in the right direction when assembling the layers (arrow in the sketch), to cut systematically with the grain when turning, which is comfortable.

Photo 5.1.4

Find below a bowl made from this disc:

Picture 5.1.5 « the two Amar » Amarello and Amaranth

109

Assembly n° 4

What’s simpler than gluing four squares to make a twice bigger square? As in the case of n° 3, and unlike n° 2, the turning becomes easier. This assemblage can be used as first coat of a two layers mixed disc. It can be the start disc of a piece (the bottom). The veining and the contrast with the sapwood of some woods (cocobolo for instance) bring out very simply the best.

Assembly n° 5

An assembly of triangulettes of the kind A, more seldom than those of the kinds B to E (look back to the beginning of the chapter 4.6) Many variants are possible, alternating woods, and/or alternating the vertex angles (in the centre). We already saw in a first example of disc N8 in the chapter 3.5 (picture 3.5.1) with the flat bottom of a bowl adorned with a «Greek». The design ensuing from the natural wood colours is a four branches cross.

A disc made of triangulettes of the kind D and E is another illustration in the chapter 4.6 (picture 4.6.2). After making an arrangement of two «mirror» discs (reversed slant) and cutting trunconic rings with a constant flare, I got the following hoped result, I chose for the cover page:

Picture 5.1.6. «Métis» Ebony and maple

Assembly n° 6

Now we pass to a 2 layers mixed disc: a full one and an open one. The full disc may be kinds 4 or 5. We shall prefer the one which allows to «make a bridge» through the joints from a layer to next one, to reinforce the glued set, and hide in the same time the joints as numerous as possible. In this mind, the kind 6 matches well with the kind 4, but not as well with the 5 one.

110

This choice favours also working with the bandsaw, as we shall see in the chapter 5.2. Find below an example of such mixed discs:

Pictures 5.1.7 and 5.1.8. Wild cherry and rosewood mixed discs

Three pieces were made from trunconic rings ensuing from these discs. The first one is flared. Go to the piece «Extra» in the chapter 8.8. The second one results from using the two remaining rings of the piece «Intro» in the same chapter. See the picture 1.13. The third one, «Intro» is closed. Two parts were turned one after the other. See below:

Picture 5.1.9. Wild cherry and rosewood mixed discs.

111

You have now only to imagine other discs open to please you conceiving and making pretty and new pieces, for instance making a 3 layers composite disc, multiplying the angles in the centre of the triangulettes, using boards themselves ensuing from assemblages, etc.

Gluing disc elements

I think resorting to vinyl quick setting glues is required. From my experience, the right firmness of a gluing depends more on the preparation and fitting of the surfaces than on clamping, but chiefly on the amount of glue, which some overuse. I will be back further over this important stage in the layered turning.

One of the sides of the disc must be very flat, with all its elements perfectly levelling. This side will become the face of the ring which will be glued on the immediate lower layer (see chapter 6). It is the one which will be below when cutting with the band saw or the scroll saw. It is easier to put the finishing touches of the surfacing of the disc rather than facing the different ensuing rings.

Making a gluing on a not very adherent flat surface, melamine for instance, is the first obvious precaution. But it’s not sufficient to avoid «mislevelling». To remedy this, we may use different methods, after scraping the potential glue burrs:

- Jointer, if broad enough, with very light cuts. But be careful with against the grain woods and ensuing stripping. Time saving does not balance the risk of losing the full disc. - Drum sander. We will be brought to surface both sides of the disc, which is rarely necessary. - Band or orbital sander. It allows winning time over manual grinding, but does not operate perfect wanted flatness. - Manual sanding on a sanding table (see chapter 4.1) flatly clamped to the workbench. It is a sure method, with no risk but a little long one; it is especially true if gluing was not made diligently enough. In order to carry out comfortably this operation, the disc must be held with a fitting handle (see photos 6.4.7 and 6.4.8), and will make «8» on the abrasive.

Generally, the forth method is sufficient enough to surface the disc, but it may be matched with the other ones when the flaws to be made up are great. The flatness is checked with a metal ruler, against the light to bring out the smallest crack between ruler and disc. Your fingers contact is the final judge.

Beware, you have not to glue necessarily all the elements! In the next chapter we will write over the dispositions to be taken as regards the choice of the pattern and gluing which allows cutting a disc with a band saw.

112

5.2 Cutting rings with band saw

It is possible to make free-hand cuttings of concentric rings in disc with a blade perpendicular to the table, if this one is not reclining. But this method brings only to make easier closing rings.

So we put ourselves into the double assumption that we have a tilting table saw to get trunconic rings, and we turn the disc around an axis to get an easy and precise cutting. We will have to make two adjustments: the inclination to the splay angle «i» and the sawing radius. We shall begin to remember you what the angle «i» is:

Fig. 5.2.1 Splay angle and sled

Then, see below a sample of a tilting table, controlled by a wheel and a rack:

Photo 5.2.2

The precision of the tilting adjustment is not an essential condition .For a 36 mm disc height, a 1° error involves 0,1 mm error only on the ring radius. Moreover, the angle is not the outcome of a calculation, but of a reading from the blueprint, which precludes «decimal points». A 1° adjustment precision is considerably sufficient.

113

But It is important for the locking of the table to be efficient when the slant adjustment is made and this without affecting it. This adjustment will be made once the sled is set up, thanks to a home-made bevel square as shown in the picture 4.1.7.

Photos 5.2.3 et 5.2.4

Slant adjustment. On the left the bevel square is wedged to avoid for the best a parallax error. The flanged bevel square is better by far (photo 4.1.7).

This sled must allow positioning a centring pivot of the disc at a precise distance from the ring, its outside lower radius read on the sketch (a trunconic ring has 4 radiuses, 2 lower and 2 upper ones). Two choices are possible: either you slide the entire sled in regard with the blade, or you slide a pivot bearing a ruler in a groove of the sled you first fixed to the table of the machine Here, you have a sample of every choice:

Photo 5.2.5

An example of a sliding sled, in a reversed position. A runner against an edge of the table, a stop device on the other side, a micrometric setting screw into a hole tapped in front of the third one, and …a holes series on the other side, to insert the pivot.

114

Like for the slant, a great precision is not necessary, even if it is desirable. A 1 mm error on a ring may be accepted, except if we were especially tightfisted with the raw thickness on the blueprint.

Several people may like the pivot of the kind «gramophone needle» or «compass tip». I prefer a bigger diameter pivot (5 mm), like a cylindrical shelf tab which fits better to the “triangulettes” discs and makes easier the realigning at every cutting (we are working «blindly», central hole of the disc underneath).

Photos 5.2.6 et 5.2.7 The sled in the working position and the detail of the places of the pivot, with 2,5 cm regular gaps. A very precise adjustment is made thanks to the control threaded rod.

Every place of the pivot is marked by a diameter line. The radius adjustment is made by inserting a millimetre ruler between the blade and one of the lines. The holes are roughly lined up along the axis of the middle of the blade, which can vary a little in accordance with its own adjustment.

Beware when adjusting the position of the pivot: changing the tilting alters the radius. Therefore the slant adjustment must be first.

In order to allow inserting the blade, and then adjusting the radius between the 2,5 cm gaps you have to make ten cm long about not very wide opening. By restricting the dimensions of this opening, you will have a well supported disc.

You can see the second kind of table on the following picture.

115

Photo 5.2.8 (MH) A fixed sled, screwed on the table. The pivot is borne by a runner, stopped after adjusting the cutting radius.

You will choose a narrow blade (8 to 12 mm), with a good saw kerf, the minimum cut radius being 4 cm about. Beware: don’t stretch the blade too much. It’s needless and it makes easier breaking. You will remove the «opening cover» around the blade which is not necessary because of the presence of the sled, and which could wedge the blade when a pronounced tilting.

We have to think right from the design of the disc of the manner we will have to handle to insert the blade. Here are three first manners to get onto the problem:

Fig. 5.2.9 3 first manners to insert the blade.

On the left a whole disc. The blade meets the cutting line by approaching askew. Why not? It has the merit of straightforwardness. But this manner of working leads to coming on the piece of a slanting joint which will be difficult if not impossible to hide.

116

Moreover, and above all, we must begin by inserting the blade, bringing it in a good position, and only at this moment we can insert the pivot «blindly», with a possible gap between the place of the pivot as it would be according to the line of the ring and as it is really. We must not forget actually that the upper line is not the same as the lower one, bearing in mind the inclination. So it is not an easy job.

We have to add, that as the table is tilted, we insert the blade into a quarter cone, which makes this delicate operation still more difficult I think I proved it is better to give up this method especially as the one I shall advocate is very simple, asks for no additional work, except while starting a little thought.

It is very difficult to keep to the line of the upper circle, the one of the lower circle (we can’t see) while remaining centered.

Let us turn to both other first manners. In a first approach, the views in the center and on the right schematise a reliable, very «mechanical» method. It consists in planning dismantling the disc into two parts, everyone drilled or marked in its centre on the underside, by adding a graft (temporary, by inserting a glued piece of paper between them) on the smaller part. The center of the smaller part is found easily with a compass if we took the precaution of drawing a centred circle on the underside of the full disc, dry fitted, before putting the graft.

But there is a simpler fourth, just as efficient, manner. After testing, I chose it. The disc is prepared into two parts, according its design (see chapter 5.1) as on the above sketches. In the center the patterns 1 and 2 and on the right the patterns 4, 5, 6 in the figure 5.1.1. For the time being, let us forget the third one which will take its good place in the chapter 5.3.

The bigger part, the one which raises no problem as regards the central drilling, is inserted into the pivot. Cutting starts on a few cm. Machine switched off, we place side by side the smaller part with a sticky tape, and we finish cutting the whole circumference,

At the time of the next cutting, we have no problem to reconstruct the disc if we are in the case of the central sketch, thanks to the two lines of the previous cutting which are used as guides, on either side of the smaller part. This reconstruction at every revolution is still simpler in the case of the right sketch: it suffices jointing the two parts and scotch tape them.

On the next page, a sample in a picture:

117

Photo 5.2.10 Cutting a disc into rings with a band saw. The smaller part is linked to the bigger one with a packaging sticky tape, the time of a roundabout ride. The pivot is out of sight under the disc

An important operation remains, actually preliminary to the previous one. Whichever the pivot, the disc must have in its center, underside, a mark or a hole immutable from a sawing to the next one. Apart from having a very reliable millimetric runner in the case of a fixed sled, we have indeed to remove the disc to adjust the next radius and slanting angle. A crossing hole would be much bothering aesthetically in every case when the central smaller disc is kept as bottom of the piece.

If we choose a pivot of the kind «compass tip», driving a spike in with a hammer is sufficient to mark the place. We shall draw our inspiration from what is dealt a little further in the complex cases (lack of material in the center) if we want to keep this kind of pivot.

I was much satisfied with the following pivot:

Photo 5.2.11

118

It is a very simple trade shelf tab. 5 mm diameter. Overall length 16 mm. The flange in the middle is very practical. It avoids drowning the pivot if the hole is to deep, and we can be sure of an unceasing gripping inside the disc which does not run the risk of getting away. A 10 mm deep hole is plenty sufficient. The diameter is the same as the diameter of a trade wood drill. The flange finds its place into a milling hole, sled side and disc side.

So we have to make a small hole in the center and underside of the disc to be cut into rings. Don’t make a mistake on the designation of the underside and label it in a very visible manner, chiefly if the central final disc is kept. Centering raises no problem with the discs of the kind 1, 2, 3, and 4 in the figure 5.1.1.

On the other hand, centering is not obvious with the discs of triangulettes (kind 5 and 6 in the figure 5.1.1), principally in the case of the triangulettes of the kinds B, C, D, E in the figure 4.6.1. Here’s how to handle about it.

At the beginning, you gather steadily together the two parts of the disc with a sticky tape on both sides, outside the central area. In order to locate the center in this mess of triangulette points, the simpler and more efficient manner is gluing on the central area of the disc a piece of tracing paper. So, we keep the vision of the drawing made with the triangulettes. Either «at eyesight» or using a few diameter pencil lines, the center is located (or better restored) with all the suitable precision. The passage under the drill raises no problem. Once the tip of the wood bit is brought into line, the disc is wedged on the table with clamps, and then drilled. Drilling is not necessarily running through (interesting if we want to keep the central disc inside the turned piece). The tracing paper is destroyed, but it does not matter, we don’t need it anymore.

Photo 5.2.12 Partial drilling of the central hole. The clamps are missing on the edges.

119

Before removing the disc, mill the hole head like shown below, in order to case the flange of the tab making a pivot.

.Photo 5.2.13

The centring hole is milled to house the flange of the pivot in the picture 5.2.11.

Several complex discs ask for an additional operation: grafting a trunnion in the center to correct the lack of matter. Here is an example:

Photo 5.2.14

The overlapping of the slanting ends of the triangulettes leads to a lack of matter in the center and makes necessary grafting a trunnion which will disappear in the finished piece.

In the case of mixed discs (full and open), we should be well advised to drill the full disc before gluing the elements of the open layer.

Once this drilling operation is coming to an end, the disc is ready to be cut.

120

5.3 Cutting rings on the lathe. The «troncoline»

Cutting rings (trunconic or not) on the lathe from discs is well tempting, for it takes out every closing problem in a full ring. Yes, but …what are the drawbacks? The first one, as we shall see, is the limitation of the disc thickness. And then, everything is depending on the tool we use and our skill. And is this limitation a true handicap? No, for in practice, the used layer heights are not huge, except when pyramidal layers, which are not aimed here. The second one, is the impossibility of cutting a mixed disc (having an open layer), as a cutting on the lathe matches only with full discs, because of unavoidable stripping when the cutting tool meets with gaps. We are not entitled for “mowed” or “sliding” cuttings, which permit avoiding this problem when turning a piece having many gaps, natural or not. But we do not use every day mixed discs, and the negative argument is mostly fading. The third drawback would be about the effect on the limit splay angle and the loss of wood, the cutting tool being necessarily thicker than a usual band saw cutting line and much thicker than a scroll saw cutting line. We have to go further into the detail to know if this argument is valid or not. Turning back to the trunconic theory is necessary, and you will find hereafter the two drawings we are interested in, where the cutting line thickness (saw kerf) is taken into account, on the contrary of the approximation in the chapter 3.3.

Fig.5.3.1 Detail of an oblique incision. To be compared to the figure 3.3.5

The cutting line width, marked «d», is the one of the used tool, increased by possible vibrations. The first effect is about the limit angle imin the sine of which raises in proportion of e+d, with a constant layer height. When an angle sine rises, the angle raises too for values between 0° and 90° (sin 0° = 0, sin 90° = 1)

121

A usual «e» value is 10 mm. Suppose a 3 mm «d» value. If the value of imin is for instance 20°, it will go, after calculation, to 26°4. The increase is not unimportant. We lose a little slimness of the piece (a flared piece has a low slimness). Otherwise, we lose more wood on every ring, as a result from the same disc, we run the risk of losing a layer that is to say a ring width on a disc, when we raise too much the saw line width.

The cutting line depth, marked L in the figure 5.3.1 changes according to the splay angle «i». When «i» is small, the increase is low. But when «i» reaches 45°, the cutting depth goes to h x 1,414, which is not unimportant. We are reaching perhaps the physical limits of the cutting tool, and therefore the limits of the process.

Let us now see what the impact is on the drawing, through the following example:

Fig.5.3.2 Example of a drawing of a trunconic work showing the impact of the cutting line width. To be compared with the figure 3.3.8

As you can see, this is not changing for much in the manner of running the drawing. It is sufficient stacking up fictitious rings, where the wood thickness «e» increases by the cutting line «d» at every layer.

After having run the process down, let us see what its advantages are. First, as I wrote before, we get rid entirely of the difficulty of closing a ring in a full turn, this difficulty having to be solved with every separated segments ring. The radiuses are precise and the circles perfect. The ring comes ready (at the gluing stage) from the cutting operation as regards its geometry.

122

Moreover, as we shall see, the visible side of the disc, we plane perfectly and quickly on the lathe, corresponds to the part which will be glued on the lower layer. There is no need to plane this face by sanding out of the lathe (chapter 6.2). At the end of cutting, we may glue directly the driving stump (or waste disc) of the future piece on the central part of the disc remained in place. The starting centring is perfectly secured with no risk of mistake (see photo 6.3.1).

At last, and chiefly, the argument in favour of cutting on the lathe is the entire freedom in choosing the kind of disc (Except open). It is no more necessary for the disc to be cut into two parts. We shall be able to run very free assemblages, as the one of the kind 3 in the figure 5.1.1 or in the next figure 5.3.3, got from single wood or composite “triangulettes”.

Fig.5.3.3 Triangulettes disc of the kind 7. «The mill». See figure 5.1.1

Here you are now convinced, I hope so, that the technique of cutting rings on the lathe deserves using it, the balance advantages-drawbacks being overall neutral, and chiefly because this technique has no substitute, for some aesthetically enticing discs. We shall come now how to handle the matter.

The problem comes simply up: respect in the same time, at every incision through the disc, the radius and the cutting angle which are just taken down from the drawing. Exactly like cutting with a band saw, a very great precision is not necessary. But it’s not at all a reason to do anything!

Installing a disc on the lathe

The installing choice is not insignificant. -The rings and the central disc must not bear grabbing marks (screw holes), which get rid direct seizing on a faceplate, apart from cutting a square screwed by its four corners on a waste disc. -We must be able to drive cutting to a small diameter of central disc. -After every incision, the remnant of the disc to be cut must be held firm. -If the disc is thin, it must be supported in order to avoid its distortion. -At last and chiefly, avoiding stripping of the wooden fibres at the end of each incision is absolutely necessary. The continuous contact with the support is necessary. 123

All these joined reasons drove me naturally to take the following solution: the waste disc.

Fig.5.3.4 Faceplate, waste disc (martyr), glue and paper.

We shall choose for the waste disc a material which respects the cutting tool, as plywood or medium, and avoid if possible the melamine. Vinyl glue suits as regards gluing with inserted paper. The choice of the paper is not important. The usual typing paper suits perfectly (coloured one is better).Its advantage is: it makes possible drawing the center of the circles and the axes with a pencil on the lathe in order to be able then to build the disc on the waste block out of the lathe. So the centering of the disc is perfectly secured with no difficulty. Once, when all the cuts are over, the rings are plucked off one after the other, by tapping with a mallet on a large blade knife as per the picture below.

Photo 5.3.5

Drawing the different radiuses

Whichever the incision technique is used, we have to draw all the rings on the visible face of the disc after it was well planed and sanded (coarse grit). This side indeed will be glued on that of the previous layer. The dimensions of the different radiuses are taken down from the drawing, for instance with a calliper, from the center. The width of the cutting tooth is such as we have two lines every incision. Of course, we took notice of this when setting the drawing in order for the glued sides to correspond. But at the time of the incision operation, one line is sufficient to adjust the position of the tooth. We shall have to choose the same side of the drawing, the most practical one to aim the tool.

124

It is not necessary to draw a full circle. A little line perpendicular to one diameter only is sufficient. At the time of adjusting the radius, turning the disc by hand to bring it at the level of the tooth is sufficient.

The cutting (or incision) tool. Grooves direction

We are starting from the idea that we want to make an incision as narrow and as deep as possible, which is contradictory because of the pliability of the cutting blade. The tool height plays an important part, since we have a circular groove. An even very thin tool wedges if it is too high, and a faintly high tool lacks stiffness and resistance to the vertical cutting effort. However, a speed steel tool body (HSS as High Speed Steel) is brittle and I think this solution must be turned down. We look for an end blade with an as long life as possible, uneasy to get with usual steel. The trapezoidal shape is to be made, wide on top, narrow underneath (see following figure 5.3.6) We can find in the trade trapezoidal steel HSS bars, 3 mm wide tipped. It is possible also to make one by chopping and grinding from an alternate industrial metal saw or a plane blade... Cutting a tooth and its extension into rejected blade of a portable circular saw is the simplest. It is the best compromise between the above listed different constraints The steel of such a blade is easy to machine, to bore. In the case of stripping, it becomes warped without breaking and it is possible to rectify it. By grinding (green or diamond impregnated grinder) we can give to the tooth the shape we want, such as for instance the tooth of the underneath figure at the bottom on the right.

Fig.5.3.6

In accordance with my experience, it is convenient to increase the «bite» by a small passage on the grinder angle, which raises the nose, and then remove the lateral sharp angles. A rounded end shape (view from top) avoids stripping and the tooth better guided into the groove is less vibrating.

125

Note. If we opt for a rapid steel bar, it is possible to carry on the research of the best drill by giving further to the tooth the shape of a mini gouge, with a thin chopping disc passed over the upper end, in the axial vertical plane.

You know you succeeded when you hear no very disagreeable shrill noise anymore while cutting. The anti-noise helmet is not the solution. We have to remove the source of the noise. You will discharge then pretty shavings, but not sawdust.

On the left in the figure 5.3.6, the disc is in a front view and the tool is inserted into a groove. With no necessary comment, it is obvious that the best position is the N° 2, where the horizontal axis of the blade is at the level of the lathe axis (the blade is assumed to be vertical). It is obvious also that with grooves of the same width the tool passes more easily when the radius is getting longer. (N°2 and N°4)

It is a first reason of pointing the grooves splaying towards the head stock as in the figure 5.3.2 rather than the contrary. As the blade proceeds into the groove, it runs so more easily. It cannot remain wedged. If it was running in front, it will run behind. The second reason is that the side intended for being glued on the next layer looks at you. So it is ready, clean and well planed for gluing while the other side is coated with glue and paper. At the end of the operation, as I noted above, you can glue directly the driving stump of the piece and round it, with no dismounting. The incision depth is limited only by the length and the resistance of the tool you use. The more it is long, the more it tends to vibrate and loose its shape under the effort of cutting. We must not forget to take notice of the splay angle that, with a given disc thickness increases the distance to be run.

We have now a blade. We shall extend it by fixing it on a blade rest, and use such a tool. We shall develop the methods, starting by the absence of additional accessory to the most complicated one.

With no accessory…or almost

The radiuses are drawn on the disc. As regards the adjustments, we «have only» to put at the right angle the tool that is just made and keep it in the good direction during the incision.

We can find in the specialized literature the depiction of a very rustic method (figure 5.3.7 below). We use a narrow mortise chisel we fix on a protractor handle. We swivel the protractor to the wished angle and we wedge it in this position. It «suffices» later to push the mortise chisel while keeping the protractor right side parallel to the disc. The eye only can guide the tool. And that’s all. It’s not easy to do, but it’s very simple in the principle.

It’s up to you to deem if you suit this method…It’s not my case, as you will understand when reading what follows.

126

Fig.5.3.7

Guiding block

It’s simply possible to slide the mortise chisel into an open towards the top U groove, made at the right angle into a wooden block directly fixed on the tool-rest, but there is better and just as simple: the above depicted «blade», bored with two fixing holes is fitted into a hard-wood square. The blade outcrops the lower side of the wood block in order to be well sustained. A reversed U wood block, pierced with a groove as wide as the wood square which makes a handle is fixed (sticky tape, spring clamp,…) at the wished angle with the help of a bevel square on the table of the lathe disc sander. One pushes, and that’s all. We win in precision and comfort over the previous method. The tool is guided by its four sides.

Fig.5.3.8

127

«Both sides» successive working method (or «front-back»)

This method is depicted, with photos in support, by Mike Darlow page 21 of his book «Woodturning Techniques». It is ascribed to Bruce Leadbeatter. Rightly starting from the almost unavoidable stripping when ending cutting and rather than choose a waste disc, the inventor prefers working the disc first in the front and then in the rear (or the contrary) thanks to an ingenious but a little difficult to make accessory, chiefly by a wood worker. Find below the sketch of this accessory.

Fig.5.3.9

We can put forward the following drawbacks - The difficulty to make such an accessory, relatively complicated - The limitation of the size of the disc. To increase it, it is necessary to lengthen the two supporting shafts of the drills. The vibration risk increases considerably and the device becomes heavy and hard to tidy in the workshop up! - The limitation of the cutting angle, for the same reasons, and it is moreover necessary to increase the distance between the shafts. - The offset of the device in comparison with the lathe bed, which can only help the vibrations. - The need of two blades instead of one, as the two blades must be perfectly lined up, including during the incisions! - The limitation in the field of the small radiuses because of the presence of the driving chuck. - The kind of gripping the disc which needs either gluing a waste stump the centring of which is hard enough, or damaging the central disc with screw caps.

On the other hand, with a same cutting tool, we can think of doubling the depth of the grooves. This can become interesting in a few cases. This is the alone advantage I give to this accessory.

128

My first «troncoline» (wood-aluminium, no connecting rod)

It’s the first prototype I imagined, starting from the previous theoretical analysis, and using techniques easily accessible to every normally equipped wood turner

Incidentally, I invented the name from «tronconique», as “trunconic” (truncated cone shape), since it is the aim of this accessory to make trunconic rings.

Other patterns may be imagined from the same base ideas, and to make the difference between them and the prototype, we shall add to them a word or a locution. We have so an overview of the original «troncoline», made mainly with wood and aluminium:

Photo 5.3.10 Overview of the original «troncoline» fixed on a lathe

The cutting tool was removed from a portable circular saw blade. The teeth of these blades are narrower than the teeth of stationary saws. It is clamped with two bolts into a hard wood bar running in a piece of aluminium tube. As for the rest, the photos talk by themselves. The operating arm is deliberately long, in order to ensure a good gearing down of the entry motion into the wood.

The supporting table is for a wood turner the most delicate part to be made. The steel bar must be welded well square with the steel sheet base. Two magnets will make easier the welding work.

If you want to avoid welding, you may build a wood frame you will fix directly on the lathe bed. The solution of the welded plate is less bulky. Fixing on the lathe is very fast and easy thanks’ to the banjo (or saddle).

129

Photo 5.3.11 The supporting table from bottom

Due to building, the runner is in a parallel to its rest. The expected splay angle direction is adjusted by inserting the bevel square between the disc and the runner rest. Angle transferring between the sketch and the machine is made easier. Moreover, it does not matter if the rim of the supporting table is not perfectly in a parallel to the disc. I am starting indeed from the principle that the angle is changing from a layer to the next one and so it is useless to keep it from an incision to another one.

Photo 5.3.12 Detail of the runner from top

The bakelited plywood has the merit of being strong and wear-resistant. We can well work it with a router in order to make openings. A small curved opening, out of sight on the photo, allows the free motion of the shaft in regard of the runner. A connecting rod would be more «mechanical», but would complicate making a wood-aluminium troncoline (this argument fades as regards the steel troncoline depicted further).

130

I think useful an explanation concerning the shape of the curved opening. I made a mathematical analysis of this geometrical problem very simple to be set, but very difficult to be solved.

In order to avoid an unnecessary effort perpendicular to the blade-rest which could have a propensity to bring a trouble for this latter to slide, the «opening» in which the coupling pivot is trapped, must remain perpendicular to the blade-rest in all its positions. If not, the opening/blade-rest angle must remain as near 90° as possible. . To reach this aim, I have to suggest you two approximate solutions, the A and B ones shown on the following picture 5.3.13.

Fig. 5.3.13 Opening of the operating arm. Two purely practical solutions 1. Operating arm. 2. Blade-rest. 3. Trajectory of the blade-rest 4. Pivot linked to the supporting table 5. Pivot linked to the blade-rest making the linkage with the operating arm. 6. Rectilinear opening. 7. Parasitic angle ensuing from the rectilinear opening 8. Curved opening

Let us note that the position of the pivot «4» is not the same one depending on whether we choose the solution A or the solution B. The shape of the opening «8» is got by the drawing only, seeing to it that, as written above, the curve remains as perpendicular as possible to the blade-rest in every position of the operating arm.

131

Don’t look for: it is not an arc of the circle. And if the sought condition is not perfectly respected, never mind. A parasitic angle is not bothering if it remains small.

Photo 5.3.14

As the supporting table is adjusted and locked at the right level, we slot the blade (while keeping a 1 to 2 mm setback), the angle is roughly adjusted and the tooth is applied on the wished line. By leaning against the tooth, which makes a pivot, one adjusts finely the angle with the bevel square. One locks. The troncoline is ready to work. It is simple and efficient.

During cutting, one leans against the table. One hand swivels the command lever, and the other one works in opposition to it. So, at the slightest hitch, at the first suspicious noise, the hand in opposition pushes back the lever in the minimal time, which is not allowed with a screw command. It is also very practical to clear regularly the groove.

We realize that the incision arrives to an end at the sight of the shavings, which becomes a blend of paper and glue. This does not prevent to draw a mark on the runner in order to know the working progress. This troncoline gives a lot of satisfaction with use. We can work 50 mm deep incisions, with very sharp rims. When deeper, a stiffer tool is necessary. One will cut it into a thicker stationary circular saw blade.

Two whole metal «troncoline» examples

We can imagine many variants of troncoline As regards the lovers of engineering and the «good welders» the temptation of making use of this idea and making a wholly metallic troncoline is great. Here you have two examples, at the stage of prototype, made by Michel Havard after seeing the above wood-aluminium «troncoline».

132

Photo 5.3.15 (MH )

The connecting rod which links the operating arm to the tool is a good mechanical solution. It gives suppleness to the movement. But it is more difficult to carry out when using the wood-metal solution.

Here you have another «whole metal» troncoline made by Michel :

Photo 5.3.16 (MH)

This time, the progress of the cutting tool is made by a threaded rod moved by a crank handle. So the reactivity of the operator in the case of an incident is reduced and the clearing operation is longer. On the other hand, the progress is completely under control. If the «thread» is 1 mm, 1/20 crank turn (a 18° rotation is perfectly perceptible) makes a 1/20 mm progress of the drill.

133

The compound table.

We forget now the troncoline and we turn ourselves (?!) resolutely to the mechanics. The purists will scream, but why using a compound table would be reserved for the engineers. We can find nowadays by the trade very reasonably priced compound tables, in the region of four jaws chuck , and even much cheaper. Fitting this tool on your turn bench takes the longest time. It is sufficient then to assemble the blade-rest depicted at the beginning of this chapter; Neither the precise pointing on the drawing of the radiuses, nor the rotation adjustment raises a problem. The machine is weighty and steady. There is only to turn the crank handle. And use this fitting to turn the stone, but that’s another story that Barnabé Ferré will perhaps relate in a next book. Here is his assemblage which needs no comment:

Photo 5.3.17 (BF)

I must give you an important notice concerning the progress of the toot with a screw.(photos 5.3.16 and 5.3.17): When pushing with a handle, we control the thrust proceeding from the progress: it is the contrary with the threaded rod..

Those three «whole metal» machines (photos 5.3.15 to 5.3.17) are weighty, bulky and, chiefly concerning the two first ones, are not in the reach of everybody as regards the set of tools and the necessary engineering deftness

My own whole steel «troncoline », with arm and connecting rod.

Although my wood/aluminium troncoline of the photo 5.3.10 gave me a great satisfaction, I had the temptation of making a «whole steel» prototype, making use for the best of the adjustment possibilities of the lathe and its banjo (saddle), as well as the results that my wood turner friends interested by that layered turning technique

134 got. The adjustment movements can be broken down, whichever the troncoline, into 4 translation movements and one rotation. The banjo and the supporting rod allow alone 3 translating movements and a rotation. The fourth translating movement (one sole variable during an incision operation) is ensuing from the sliding of a blade-rest into a sheath, under the effect of an operating arm. I took the connecting rod solution to link the blade-rest to the operating arm, better fitted solution to machining than the opening one.

You will find in the following pages a summarizing card ot the operations to be made for every ring, as well as explanatory photos. A clamped ring on the supporting rod allows adjusting the tooth height once and for all as we don’t change the blade.

Metallic troncoline on rod Protocol for the tappet aiming

Marking - on the disc placed on the lathe, glued on its waste disc and well surfaced, draw the center carefully ( 2 beginnings of perpendicular diameters) - Remove the lathe (it’s better working on the workbench) and draw a diameter with a rather colored sharp spike. - Transfer very accurately on this diameter the cut radiuses taken from the drawing with a calliper. The drawing of the full cut circles is useless and may generate an error. A point or a small line is sufficient.

Height of the tooth - Put back the disc on the lathe. Slide the troncoline into the banjo and check how high the cutting tooth is in regard to the turning axis If needed, amend the height of the support collar of the rod on the banjo. This height remains unchanging as long as we don’t change the lathe, or the tooth.

Approach of the disc - Put the banjo in a perpendicular position to the work bench. Help yourself with a subsidiary saddle that was made according to the dimensions of the lathe bench. In the same time, the tappet must be positioned basically to the required angle in regard with the disc. - Tappet slotted, slide the banjo and the subsidiary saddle along the bench until the base comes almost to contact the disc (1 to 2 mm). Lock the subsidiary saddle. Note : in the case of a great variation of the cut angle, there is a possibility that this operation has to be made again for the tooth to be as near the disc as possible in the starting position of the runner without the base rubbing the disc.

Adjustment of the cut angle - Position towards the front of the disc a horizontal ruler at the level of the base with the help of a small clamp. This ruler must protrude largely towards the front of the disc in order to allow the following operation. 135

- Leaning against this ruler on the one part, and on the base on the other part, we place flat the bevel square after it is adjusted as per the drawing A leg is leaning against the vertical side of the disc and follows the alignment of the ruler. The angle is obtuse. - Free the rotation in regard of the banjo, swivel the tappet until it becomes parallel to the second leg of the bevel square. If needed, go back to the previous chapter «approach of the disc». As a variant, it is possible to do without the ruler and align at sight a leg on the side of the disc, the other one remaining leaning against the tappet.

Adjustment of the cut radius - Disc remaining locked, position a horizontal thin ruler on the rear at the level of the axis, the bevelled end looking forward, aiming the wished radius. - Slide the troncoline along the subsidiary banjo until the tooth is leaning on the bevelled end of the ruler (the bevel helps this adjustment, chiefly for the great angles). Check the angle for the last time .Remove the ruler. Lock the banjo and release the disc. As a variant, with no help of the ruler, aim directly the right side of the tooth towards the corresponding point of the right radius, then lock the banjo and unlock the disc.

The adjustments are over. Cutting can begin

And now, my own whole metal (steel) troncoline, described by pictures.

Photo 5.3.18 (RM) My whole steel troncoline in action

136

Photo 5.3.19 (RM) The accessory out of the lathe

Photo 5.3.20 (RM) Dismantled accessory

137

Photo 5.3.21 (RM) Taking down the angle from the drawing

Photo 5.3.22 (RM) Adjustment of the angle. See photo 4.1.7

Photo 5.3.23 (RM) Radius adjustment

138

Photo 5.3.24 (RM) Subsidiary square-banjo guiding the banjo when adjusting the radius

It’s up to you to choose your kind of troncoline. You will find perhaps your «happiness» by combining cunningly all these ideas and techniques. Or you can find other ones... Anyway, you will be attracted by this principle «try it and you will adopt it», I am persuaded. And all this, what to do with? I end this chapter giving you an example of a piece made from a two layers composite disc of the kind in the above photography 5.1.4. I gave it the name of «embrouillamini» (muddle) because of an obvious reason. It is difficult to find one’s way into this tangle of segments, each one different, These chosen woods come from zebrano to wenge.

Photo 5.3.25 “Embrouillamini” Try to do the same with another process!

139

5.4 Cutting rings with a scroll saw

We can find today high standard scroll saws with an acceptable sawing height, at reasonable prices. We have so good reasons to look into the case of this tool usually reserved to marquetry and puzzles. Is it not well fitted for cutting rings into a disc? We see further that the case is not as simple.

The recent scroll saws are equipped either with a swivelling table (between – 45° and + 45° depending on the models), or with an engine block pivoting in regard to the table which remains fixed. This last model is more convenient as regards the slanting cuts which affect us, as the disc to be cut does tend to slide when sawing because of the incline of the table (if it is not stopped by a pivot).

A scroll saw allows making a great part of what was described above concerning the band saw. Only the very thick discs are out of the field of its application.

But, because of the narrowness of the blade, the scroll saw gives an additional opportunity: starting full cutting a previously bored solid disc

It is the successfully used method of Carole Rothman she depicts in details in her book published in the year 2000 and called «Wooden Bowls From The Scroll Saw». As when working with a band saw, the table is slanting, and we can cut trunconic layers, then glue them by piling them, to make a piece which will be simply sanded inside as outside, without resorting to the lathe. So we can tackle to original shapes, come out of the «all round» field. An unattractive (in my view) disadvantage common to all these pieces: the bottom of these pieces is flat.

This cutting method offers a major difficulty as soon as the disc is a little thick: drill a as small as possible hole exactly at the ring edge, with a skew attack and slanting to the chosen splay angle. A pretty challenge!

The figure below is sufficient to explain why we have no interest to choose a too small wood drill. This is going in the good sense for a bigger drill is in the same time stiffer and longer. On the other hand, we lose a little more wood when turning to pull out the marks of drilling. You have to find your good compromise.

140

Fig. 5.4.1

Drilling a disc for the passage of the scroll saw blade. The margin is not very large!

So the waste of wood is at least the same as the losses of the troncoline in the previous chapter, execution easiness missing. If we choose the free hand work, a preparatory lay-out is necessary, with a compass, but it is less precise than a lay-out on the lathe. However the careful tracking of the line is not sufficient, we have to respect all along the sawing the centre position (virtual and free hand), otherwise the hidden radius of the ring fluctuates.

A variant, previously moved away in favour of the band saw, can be considered with a little more chance of succeeding for the scroll saw, thanks to its blade narrowness and the easiness of free hand work (easiness that does not cancel the above inconvenience that we have to respect a virtual centre): starting the sawing by a radial cutting, followed by a right angle tight bend. Refer to the left sketch in the figure 5.2.9. But because of the incline of the table, starting begins always by a quarter cone, which complicates the process much as the inclination increases. And the joint on the piece, although thin, is always slanting. To console ourselves, this makes easier and strengthens gluing. This gluing of the radial cut allows reconstructing the full ring and is made at once after cutting, by playing on the wood resilience to insert glue with a small brush. As a preparation, blowing dust out is sufficient. The radial cuts are offset from a ring to the next one, not to weaken the piece and forget the joint at the most.

To get a precise cutting of the rings, and prevent a possible clumsiness, we are naturally tempted to resort to a sled which allows positioning a pivot… and we saved no advantage on the band saw, except if we have one and not the other. And we saved nothing at all on the troncoline, which requires only a lathe... and if there is no lathe, there is no turning and... no turner anyway! No need to read between the lines to understand I am not an enthusiastic supporter of the scroll saw to cut trunconic rings into full discs.

141

5.5 Cutting trunconic grouped merlons. Cutting mixed discs

The interest of the principle of cutting discs into trunconic rings runs beyond getting full layers, either simple, or double, or even triple... mixed, composite or not.

This principle applies happily and successfully to openwork with the two following cases: →The machining of grouped segments which are to become «merlons», the full parts of an open layer. . →The machining of mixed layers including at least one open layer.

Cutting techniques are just described in the previous chapters. Not all of them can be applied. The band saw and the scroll saw are welcome, but I think the troncoline must (unhappily) be banished because of the gaps the tool meets and the unavoidable stripping at the cutting end. Samples allow estimating all the additional interest of cutting discs into trunconic rings, should they be full or incomplete.

Grouped trunconic merlons. Wild cherry bowl.

Let’s take the example of the very simple open bowl «Tête Bêche» (head to foot) in the chapter 8.6. Here is this bowl in the process of turning:

Photo 5.5.1

Let’s leave the rough aesthetics of this piece out, which fails to come up to expectations, and let’s retain only the technical angle which was the reason of making it. Merlons are ultra numerous and it would be a grind working them one after another. For cutting grouped " triangulettes" I chose the first of the two following methods:

142

Figure 5.5.2 Two methods of cutting grouped triangulettes into trunconic merlons. On the right, the triangulettes are glued on a waste disc, but not glued with one another.

With the reversal method, the machining from a board of triangulettes having the same vertex angle is particularly faster as the presence of gaps (crenels) lets a good scope for respecting this angle. By grouping them as on the left sketch, we get:

Photo 5.5.3

The left incomplete disc corresponds to the lower part of the piece, the one on the right to the upper part. Moreover, the sketch of the piece allowed us to cut alternately both discs with no change of the radius. Ha, laziness! A few passages on band saw, and we find ourselves with a considerable number of merlons, stained on both sides by paper and dried glue we have to pull out with a quick disc sanding.

If we choose the right assemblage (fig.5.5.2.), we pull dirty spots out on the lathe in the same time as we set up the upper side, and we are winning. See further the bowl «Quintette».

Entering the blade raises no problem; the discs are incomplete because of the openwork.

143

Photo 5.5.4 The «rings» made of grouped merlons are ready, as well as the full rings and the disc making the basis of the piece (photo 8.6).

Grouped trunconic merlons. Splayed bowl «Quintette»

By choosing the right sketch in the figure 5.5.2., which involves a waste disc, the slots (gaps, crenels) are stained on one side we will choose as upper side when assembling. We can so « kill three birds with one stone» on the lathe, while assembling layer after layer: working round the layer edges on the lathe to prepare placing the next one, remove glue and paper with a gouge, while setting up the upper side of the layer under way.

I chose this solution for the splayed bowl made with five different woods, I named «Quintette», in the chapter 8.7. Here are two pictures I carried out under execution.

Photos 5.5.5 et 5.5.6 Cutting grouped merlons from triangulettes glued on a medium waste disc

144

Mixed discs. Wild cherry and rosewood vases and bowls

Let’s turn to the two vases in the chapter 8.8 and the bowl of the picture 1.13. They are three half open pieces made from two identical mixed discs, made up with a wild cherry full layer and a rosewood triangulettes open layer (plane vertical section triangulettes). Here is a reminder of one of those pieces and one of the discs from which the layers were cut.

Photos 5.5.7 et 5.5.8 Wild cherry full layer and rosewood open layer

When gazing at the right picture, we imagine easily how much sparing work is possible with such a process, all at once as regards segments cutting and their positioning when assembling. The open effect can be increased by stacking a merlon high layer upon a thin full layer. It is also possible to alternate with no problem the woods of different triangulettes, as here vary the angles in the center, or even their kind of section, vertical or slanting...

Mixed disc. Open box «trapèze»

By staring and detailing a little more, here is a sample of openwork I made from triangulettes with a trapezoidal section. I had no problem to get trapezoids, the «reversal» completed with a blade slant (see chapter 4.3) gave me them freely!

Photo 5.5.9 Open box (reminder of the picture 4.6.3)

145

Figure 5.5.10 Open box sketch (reminder of the picture 4.6.3)

146

Pictures 5.5.11 and 5.5.12 The set of the units before assembling the mixed disc, then start this assembling on the «guillotine» (see further. The guillotine is here hidden most of the part) to trim the spaces and respect the centring.

Pictures 5.5.13 and 5.5.14 On the left, the entirely assembled disc, «offsetable» sector in place (see too the picture 4.6.4). On the right the two rings after gluing and the central disc that will become the mixed upper layer of the box.

147

6. Assembling elements and layers

6.1 Gluing and clamping

Now we know machining all the elements making a full piece. We have to assemble them by gluing and respect the foreseen disposition of the sketch and anticipate the turning constraints to come.

Settle before your well cleared workbench, the sanding plate held firm by clamps or better, between the jaws of «longitudinal workbench vice» ("presse parisienne" in French).

The elements to be assembled, duly indexed and numbered are arranged into compartments. Every surface to be glued is passed slightly on the sanding plate to remove the possible sawing reminders, and then dusted.

As regards glue, the choice is huge if we refer to the literature. It is not sure you will find easily in the common trade all the kinds that are mentioned! But happily, after experience, the vinyl fast drying glue suits perfectly, and you can find it everywhere. Then, why doing without it? YOU have to choose a good brand and keep it.

Foresee within easy reach:

- A small brush with stiff bristles to apply the glue on the big surfaces. The same brush will be useful for you to remove the glue surplus in the difficult locations. Very often however, it is sufficient to put a drop directly from the neck of the bottle and the brush becomes useless.

- Paper handkerchiefs to wipe the brush or the glue surplus easy to be reached

- A container with water to put the brushes during the breaks.

The clamping of this kind of glue is very simple, rubbing one against the other the two parts till removing the potential surplus, plucking them off and checking quickly that the whole surface is glued on both sides. Rub once more the two parts until feeling some resistance, check the positioning, and tighten with your fingers during ten seconds about. It is sufficient in most cases to glue segments with one another.

Otherwise, resort to the array of the «clothes-pegs» (pins), «stringeons» (see above), rubber bands, and other accessories that will never have the adaptability of your fingers.

As regards more important gluing, as rings with one another, a slight tightening is necessary. Why slight? Because a strong tightening creates constraints over the wood, which will take its revenge sooner or later at the mercy of hygrometry, and warps it, jeopardises the next gluing.

148

Resort to the «third hand» taken between workbench and ceiling, to well spread standard or piston clamps or even a load (stone, cast iron, lead, heavy wood…) by inserting a plank. This last manner is practical, for with a little skill we can avoid sliding an element on the next one that almost all the clamps cause.

It is advisable to admit once and for all with no limitation that a good gluing is ensuing only from a good adjustment of the elements with one another.

6.2 Ring sprung from isolated segments Or from blocks sprung from discs

Gluing segments or ring elements with no good rest and with no guide would be reckless. Let’s note that what’s following involves as well test gluing (with test segments) than final gluing, however with more flatness margin as regards the tests.

The rest must be very flat, and not very adherent. A melamine or «Formica» coated plank will do perfectly. If white it’s better for we shall draw on this plank an over simplified sketch of the ring we want to make, that is two concentric circles and two perpendicular axis (orthogonal) passing by their center, as the figures below:

Circular segments Trapezoidal segments

Fig.6.2.1 Refer to the note under the figure 3.2.2.

As ring gluing proceeds, we check that the segments cover or are at a tangent to the drawing and that the angulations are good. We see there are variants, but this drawing kind is very often necessary.

Let’s turn to examples of rings in the process of gluing

149

Blocks ensuing from discs.

The two parts of a crown cut with a band saw (or a scroll saw) are automatically fitting as regards the diameter and the angles, an advantage among others which makes seducing this process. In order to glue these two parts, a simple thrust of both hands would be sufficient. But we free ourselves more quickly from that task and it is more reassuring to make an longer effort, especially as it is very easy to do with rubber bands, as you can see in the two following pictures, at the condition to respect flatness.

Pictures 6.2.2 and 6.2.3. Tightening trunconic mixed rings

Circular segments

This kind of assembling is less simple than it seems, for we have to be very watchful when we pass the radiating sides under the disc sander in order to follow exactly the sketch; a guide is absolutely essential in this case. We have to adjust every segment after one another. This adjustment is difficult (even very difficult) as regards the closing segment if we want make the ring within a single stroke. Better it is to work on half rings.

Picture 6.2.4. Ring of «circular» segments cut with a band saw. The segments are held steady on the sketch with a sticky tape. The closing segment adjustment is difficult. Better it is to work with half rings.

150

Trapezoidal segments

The greatest difficulty, when we start in this discipline (this word is perfectly appropriate, in French), is accepting we have to compel ourselves to make test rings. Once the machine is well adjusted thanks to the tests on worthless woods, assembling quarter or half rings and being accurate (or almost...) is a very pleasure!! No test, no safety !

Photo 6.2.5 Angular test variant

Here is a well practical variant to test the right angle on a test ring. A simple typist paper sheet, two arcs of the circle, and there you have it! The paper gives squaring. As regards a test jig, for the rest to be perfectly flat does not matter. For a half-ring, use an edge of the sheet or present it vertically on a table. You can also test the ring quarters (radius and angles) with the three-dimensional square.

Photo 6.2.6 Assembling N 44 composite segments ring. «Double face» glued catches make easier this painstaking task.

151

Pyramidal segments

We take now on the greatest difficulty, for we have to work «in the space», with no flat stand, and because the adjustments have three parameters instead of two as regards the trapezoidal work. (Two angles and a length instead of one angle and one length). Here are three pictures showing the steps of setting up the adjustment of the angles β and γ and the diameter checking .

Photo 6.2.7 First step

First step.

The test segments N 24 are cut, here out of recycled melamine, in order to show well that the choice of the wood is not of great importance at the stage of the adjustments. After passing their radiating sides on the sanding table, they are positioned flatly, the outward side on top, and joined with sticky tape. Gluing is not necessary. The set is turned over and we check with a digital bevel square the angle in the centre, which must be 6 x β. Multiplying by 6 amplifies the possible absolute error, and this increases the precision of checking and the adjustment to be done.

In the same time, we measure with a flexible ruler the bogus arc of the circle made of the quarter of the great basis of the future ring, at the top on the picture. In a first rough estimate, the length of this arc must be included between 0,5 x πR and 6 x B. If that’s not the case, adjust the length stop, which works over B. After adjustments of the stop and the rotation β, go to the next step.

152

Picture 6.2.8 2nd step Second step.

The segments are sanded then joined as in the first step. The radiating sides are glued and the quarter ring is formed by using sticky tapes as hinges. We check that everything is in a good place, that the segment ends are well fitted, and we fasten (slightly) with rubber straps.

Picture 6.2.9 3rd step

Third step

As soon as the glue is setting (1 to 3 minutes according the temperature, your appetite for risk, your impatience) present the quarter ring over the three dimensional square. In this example, I did not saw the edges of the board at the splay angle «i», and it was an error, because this stops checking the got diameter with precision, and the jig is not very steady on its basis. On the other hand, every angle error is expressed

153 evidently thanks to the lateral sides of the square, and as the adjustment of β was made during the previous step, this can come only from the adjustment of γ (blade slant). If we don’t work in this manner, we don’t know whether we have to work on β, on γ, or both of them.

After the tests, we machine the final segments and we put them together as shown above, with no exaggeration over the glue. When the segments are pointed ended, as the triangulettes, the wood tends to stick up under the influence of gluing, and we have to plan clamping consequently. We have also an interest to start gluing by joining the segments 2 by 2 or 3 by 3 and by matching these two manners, we get the following sample:

Picture 6.2.10 Gluing pyramidal segments 2 by 2. See also picture 4.1.6

Other cases

It may occur we have interest gluing directly the segments on a part of the piece. We have in that case to be extra watchful, for we have then no right to a mistake anymore... except starting from the beginning. We can nevertheless reduce the risk by gluing not individual segments, but blocks of segments, as in the example below:

154

Picture 6.2.11. Example of gluing groups of segments directly on a part of the piece

Imperfections.

In spite of having made test gluing, small imperfections can affect the final quarter rings or the half rings. Why «small»? Simply because if they are great, harm is irreversible, and we have to start again …or match the drawing of the sketch to what is made.

The small mistakes or clumsiness can be corrected, but at the price of a loss of latitude when profiling. The most frequent case is the following one:

Fig.6.2.12

This flaw proceeds from a small adjustment error of the angle α. There is not much other solution than trimming the red hatched parts by using the disc sander

155 cautiously. A loss of wood is ensuing when turning, as the right figure shows it (with a little exaggeration for proving needs). If as here α is too small, the flaw adjustment does not work, or very few, on the outward look of the ring. If, on the contrary, α is too big, the trimming reduces the outward sides of joining segments, and this affects the outward look of the finished piece.

Here is an other case:

Fig.6.2.13

This kind of flaw affects particularly the pyramidal rings the segments of which we try to correct under lapidary when assembling. We must think of «marrying» the quarter pyramids before going to half pyramids. Sometimes chance makes good things, and the errors make up for one another.

6.3 First lathe mounting

For each piece (apart from repeating by copying oneself), we must think right from the design of the manner we shall run the assembling of the layers AND the intermediate turnings AND the last turning AND the finishing. That is an inseparable whole. There are among these actions some common points, and the first lathe mounting is a part of them. What are our reflection elements about this matter? - Anticipating the next chapter, assembling layer after layer is the general rule I suggest to enforce. - The inner profiling we shall keep on calling «hollowing» is easier when the piece splays out when looking at the tail stock.. - So theoretically, we shall start by the smallest diameter on the head stock. - The intermediate turnings and gluings which part them ask for (a little) time and better it is freeing the lathe during the intervals, even only to... finish the previous piece! - We want to keep intact the elements we have prepared with «love», with no screw marks.

156

The whole of this leads us naturally, apart from the unavoidable exceptions, to the following typical solution: - A faceplate which frees the jaw chucks in favour of others tasks - A waste disc which receives the screw wounds. - Gluing the first element of the piece, or the first layer upon the waste disc, through a paper leaf, which permits later to part with no problem the piece (or a part of a piece). As a variant, it is possible to glue without intermediate paper if we detach the piece by cutting the waste disc on the lathe. The first mounting directly made on the piece basis disc is an exception.

Hereunder three examples of first mountings on waste discs:

Photo 6.3.1 First mounting following cutting with a troncoline. See picture 5.1.3. On the left, the initial big waste disc, itself on a faceplate.

Further to a rings cutting with a troncoline, the starting mounting is very easy. It is immediately centred.

The great waste disc n°1 is the one which supported the disc cut in rings the center of which remains. This centre disc becomes the basis of the future piece.

It suffices gluing the waste small disc n° 2 (which will be used to drive the piece), clamping it with the headstock, and turning it round. So, the driving waste disc and the basis of the piece are already centered automatically. We detach the whole of the waste disc n°1 with a kitchen knife, we turn this whole over, and we take it into a four jaws chuck. In order to avoid this immobilization of the four jaws chuck, we can substitute a set «faceplate chuck + waste disc» for the waste disc n°2 and clamp it with a turning «funnel » headstock of the kind Oneway.

157

Photos 6.3.2 et 6.3.3 Just this one. First mounting by the big diameter. See picture 4.6.8

Turning an open lid of a box, made with thick curved triangulettes (right photo). This time, «which is not a habit», we start by the big diameter, shaped as a purpleheart ring N 12 glued on a waste disc with paper in-between. The purpleheart block in the center, as thick as the ring, is here only to allow gluing triangulettes at the right position, after making round and surfacing the ring.

Unusually turning starts from outside. See the assemblage of the triangulettes on the photo 4.6.8.

Photos 6.3.4 and 6.3.5. Two first mountings for an only piece. See chapter 8.6.

A «classical» example, but concerning a piece made in two parts, the open bowl «Tête bêche» (Head to Foot), of the chapter 8.6. Hence the both faceplate chucks. Turning the high part begins by a ring (on the left, left photo) and turning the lower part starts with a disc the small central hole of which (ensuing from trunconic cutting with a band saw) will vanish when turning.

158

In both cases, in spite of a precise enough centring on the waste disc, the first layer of the piece which is just so glued, passes again on the lathe in order to be perfectly centered again before gluing the layer n°2.

But it occurs often enough we want to keep intact the geometry of the layer n° 1 (or n° 2 if the setting is made directly on the basis disc), which forces to line up its center with the center of the waste disc or the basis disc. It’s not obvious, but happily the solutions are not missing.

Here you have three ones:

Photos 6.3.6 and 6.3.7. Starting mounting with a centered trunnion.

The second layer of the piece is a disc made of thick triangulettes the ends of which are end rounded (disc sander) before assembling. We want to keep intact this assembling, the «physical» center of which does not exist, and the «theoretical» center is a little blurred because the triangulettes are not strictly alike.

My solution: gluing in places tracing paper upon the triangulettes disc, which allows looking through to pinpoint the theoretical center we draw (2 diametrical lines with a pencil). So the center is physically located and we can turn to the phase of drilling with the pillar drilling machine in order to insert the linking trunnion between the layers 1 and 2. The disc is fixed with double sided adhesive tape upon a wood plank, itself fixed to the table of the drilling machine with clamps.

The finished piece is shown on the right picture

159

Photos 6.3.8 and 6.3.9. First mounting centered from a small trunnion..

A trunconic openwork with a varying splay angle. Joining the tips of the triangulettes of the basis disc the central part of which appears on the right of the left picture, is never perfect. Hence the small trunnion turned on demand which stands at this small unattractive space and operates the centring of the single wood basis.

Photo 6.3.10. Look back to the photo 3.5.1. First mounting directly on the bottom (flat) of the piece.

This N8 disc will make up the bottom (layer n°2) of a bowl adorned with a «Greek pattern». It was question there also to conceal the junction of the triangulettes, but as discreetly as possible. The centring of the layer 2 upon the layer 1 (the «foot») was made with a thin framer point. We may imagine other centring processes: the plumb line hung above the bench work, the laser…Your imagination will be requested in the course of a recalcitrant project .

160

6.4 Full or mixed layer

It’s off to a good start! The piece about is to be shaped! The first mounting is in place. The same to the first layer. We have now to glue the other ones. A first question is set: must we pile the layers on the lathe or out of the lathe? My answer, which is not necessarily yours, is out of the lathe ...in almost the whole of the cases. But I must justify this answer.

Between two work stages, it could not be question of dismantling from a chuck a piece under work and then taking it again. The realigning would be uncertain. The used chuck is immobilized, but this drawback is common with the work on a bench. One point everywhere!

The lathe has advantages: - the piece under work remains centered - the tailstock can be used as a clamp - the lathe has a divider which can be useful in some cases, for instance openwork design.

But working on a bench: - Is by far more comfortable. Everything is in the reach of your hand. - Allows having as an ally the gravity (or the weight or the weightiness but not the gravitation, you don’t try to put either your piece or you into orbit...). It is especially true as regards the open layers, but it’s true also for the full layers. - Makes easier the centering operation of the ring to be glued, either by going around the bench, or by turning the piece flatly on a rest (see further).

A second question is: «must we glue the layers after one another», or by blocks, or must we glue the whole piece?

I have rather the method «layer after layer» and I justify myself. Keeping the centering from a layer to the next one is imperative. A ring made of individual segments, view from top, makes a broken line not necessarily inscribed in a perfect circle. The next ring has another «diameter» in most cases and we add the indubitable advantage of crossing joints to improve the solidity of the piece and very often its aesthetics. This makes the broken lines cannot be superposed.

All this makes very difficult the direct piling of two rings raw from sawing. Only the trunconic rings are an exception.

So at least one of the two rings must be" rounded", on the lathe obviously, and there is no other solution than making it on the just glued layer.

Moreover, the layers must be very parallel with one another; otherwise we risk a «wrinkled» (accordion) putting out of shape. But the rings don’t fit, except theoretically, between two strictly parallel planes. The lower surface is approximately flat because glued upon a plank reputed to be flat, and because of passing on the sanding table. Passing under the jointer-planer could make parallel both sides, but I am not tempted, there is a too big risk. Passing under the drum sander fixed on the

161 lathe is worth only (considering time) if we pass all the rings after one another, if the operation is reliable, not destructive, etc

And what is to say about the mixed layers, topped by merlons? Do you feel to pass them under the jointer-planer or the drum sander? I see only one solution:" rounding" on the lathe the just glued ring, and plane with lathe tools the face which is about to receive the next one. By working so, you solve the centering AND surfacing problems.

The protocol of the piling operation of the layers is so described as follows:

- Making round the just glued layer on the lathe, including of course the start layer n° 1. - Then (and not before) levelling (facing) the front face of the same layer - Hollowing, with one delayed layer, to ascertain later the shape continuity at the time of the next stage. Sanding the bottom before it becomes arduous. - Passing the next layer basis on the bench sanding table (no more need to take care of the upper side). -Removing the piece under way WITH its chuck for it to remain perfectly centered -Gluing on the bench the next layer, either full, mixed or open. - Repeat the operation as regards every layer.

Let us detail this list of operations. Making round and facing (levelling, planning) the upper side of the glued layer.

Better it is to choose a valid method as well for the full layers as mixed layers, so open on the top. What is valid for the mixed layers is still more valid for the full layers. So suppose we have to make round, then levelling a series of merlons. One is confident with one’s gluing, but …it is hazardous fetching in the workshop the pulled out merlons and dangerous to receive them into the face! We must have the light hand. Only the «mowing» cuts can be tolerated, the wood running on the tool sharp edge as when you cut sausage (with the exception that the sausage is not moving...).

Almost all the tools allow this kind of cutting, but the king in this precise case is doubtless the bowl gouge. As for me, I make round with such a gouge, with a long enough bevel, and I plane later with another very shortly bevelled one. It is not necessary to make round the whole ring, inside and outside, but only to chamfer, to make round the edges (or even one only edge) so to make easier and position precisely the next ring.

Once finished the gouge work, we have to apply the sanding table on the upper side of the layer under way. A good surfacing, or planning, of this side will ascertain later a good gluing of the layer to come; we must so make it carefully.

162

Passing with chalk allows you to spot the slightest flaw, including the flatness flaw ensuing from the (bowl) gouge work in front position (picture 6.4.1).

Picture 6.4.1

The pictures 6.4.2 and 6.4.3 show how presenting the sanding table to get an (almost) perfect result, a lot better than if we apply with both hands a simple rule covered with abrasive. With the lathe stopped, we place the table on the bench of the lathe and we apply it firmly on the side to be corrected. We approach the saddle against the table sander, and we set it. Later the table is tilted till it is no more in contact with the piece. We switch on the lathe and we apply the table upon the side to be planed and in the same time we lean it against the saddle which makes a hinge and we also slide the table on the bench in order that it does not remain in a fixed position upon the abrasive. Passing with chalk the surfaces to be planed still helps you to test your work. It is sufficient to tilt the table to the right so that it is no more in contact with the piece.

Photos.6.4.2 et 6.4.3

163

Hollowing (or inner profiling)

Hollowing asks being a little less cautious, less light hand, than facing the front side. The question is delicate and will not be much developed for everybody has one’s tools and one’s preferred methods. And he is attached to them! As for me, I use rather the bowl gouge and the spindle (detail) gouge, while working «by pushing». The bevel angle is depending on the area in work: very short bevel in the bottom and longer bevel when reaching the flared areas. Of course, sharpening must be excellent and the bevel regularly passed under the wet diamond hone.

Photos 6.4.4. and 6.4.5. The tool rest and its position

And the tool rest, of which it is few written in the books? We will take care to place it as near as possible the piece to minimize the overhang, cause of possible stripping (formally prohibited!) and lack of precision of the gesture while following the curve. This is illustrated by the above photos. The curved tool rest in the photo 6.4.4 is especially convenient. Just a flat bar curved on the smithy, a 30 mm shaft and a soldering. Why do without?

Layered turning leaves not much place to fantasy when machining the piece. The errors are paid «cash». Be precise and delicate when handling the tools.

Sanding the bottom face of the layer to be glued

We saw in the previous chapter how getting a ring from segments or groups of (trunconic) segments. In spite of the precaution of gluing on a very flat rest, glue burrs and small mislevelling flaws may remain, and we can even say «remain». In order to suppress them, we shall resort to the sanding table.

The ring can be taken directly in the hand, but a handle makes easier the work, and makes it more reliable. The movements will take the shape of an 8, as those used in the pad varnishing.

164

Here is a sample of an adjustable handle you can make, and its sister in a picture:

Fig.6.4.6

Picture 6.4.7 and 6.4.8. Rings surfacing handle

Centering, gluing and clamping.

The previous layer was glued, made round in its upper part and surfaced on the lathe. We remove (unscrew) from the lathe the set «piece under way + chuck» and we place it on an adjustable rest of the following kind, really steady on the bench:

Photo.6.4.9

Later we present blank the ring to be glued on the piece under way for a last adjustment test plan over plan. We look for the best position to cross the vertical joints, marry the woods and … respect the drawing

165

We pinpoint this position in rotation thanks to a pencil line running through the plan of gluing. A diametrically opposed line is useful, but we have to differentiate it, for instance a double line or another colour. The glue is applied with a brush on both sides to be glued. The ring is put in a position close to the located one, and we make some few rotation movements to trim the glue. We line up the marks while testing for a last time a good matching of the perimeters, that is to say centering. We apply then a «medium» clamping effort, either with a «third hand» (vertical tappet) which meets to the ceiling, or with every heavy thing you have close at hand, as in the following photo:

Picture 6.4.10 On the left, two rings are pre-assembled in order to reduce the number of the phases out of the lathe, which is possible only after you have succeeded to face well both faces on the sanding table…which is not always the case. If we have to work with full layers, better it is to resort to a drum sander. The cast iron pan could be weighed down with sand, lead… but it is not necessary. As already told above, the preparatory adjustment makes a good gluing, not the clamping. On the right, the basis of the piece (2 layers) taken in the chuck inserted into the bench rest, topped with a plywood plank and a cast iron pig. Everything is heavy AND dense is well to clamping.

Picture 6.4.11 Another gluing phase of the above piece. The cast iron pig found again some service

166

Outside profiling

As all the rings are not yet glued, it is not useful nor even desirable to make the outside of the piece, which can be limited to round partially every layer linked to the re-aligning. We shall be back to this question in the chapter 7. 6.5 The open layer. The «guillotine»

Cutting out a piece is one of the favourite fields of layered turning. A piece «full with blanks» is always attractive and puzzles the layman. «How did he make this? », «How could he handle to turn with all these holes? » are the questions which come back most often. We will try to answer. But first, as always, a little theory. Let us leave the one-wood «full with holes» piece out, holes ensuing from fantasies of the nature. We leave also out the holes made with the drill or the router. Still remain the «layered» blanks arranged in order in accordance with our wish and we can arrange three groups of layers of this kind, the open layers we get by placing side to side blanks, we name crenels, and full segments we call merlons, being inspired by the terminology of the towers of fortified castles.

Group 1. Uncertainly shaped crenels

This piling is the easiest one. A layer is made with odd shaped segments, but derived from equally thick planks (or almost equally, see previous chapter).These segments (merlons) are separated by blanks (gaps) which have also an odd shape. However, we can spare turning work if we resort to circular segments cut with a band saw. It’s a privileged field of this kind of segments It’s possible to combine woods and vary as you please as well the length of the merlons than the width of the gaps. The one sole condition to be respected in this kind of assemblage is to ascertain the bridging of a merlon with another one of the previous layer. The lathe operates rounding of each layer and its surfacing as we wait for the next layer, operates too inner and outward shaping, not necessarily finished if we desire keeping flat facets. In this last case, we pass under the band saw only the inner side of the segment. A great advantage of this piling kind: we choose the sense of the grain in order to «work with it» when turning. Are you tempted? In this case, the indications in the previous chapter are sufficient.

Group 2. Crenels or merlons with parallel sides.

As we saw it in the chapter 3.2, inserting equally thick plates (little boards) between trapezoidal segments brings simply to an increasing of the ring diameter.

167

If we replace these plates by virtual plates, that is to say by blanks, the effect is strictly the same. And if we keep these plates as segments and if we «virtualize» the trapezoidal segments, we get the same result. Turn back to the pictures 3.2.8 and 3.2.9. By making yours the both possible layouts of the drawings, and combining with what is preceding about virtual and real, we get the four following cases:

Fig.6.5.1 Similar dispositions to the one of the figure 3.2.8. One sole lateral side of the merlon is radiating

Fig.6.5.2 Similar dispositions to the one of the figure 3.2.9. The symmetry axis of each merlon is radiating.

Of course, the segments have the tangential dimension (the other dimension is said radial) necessary to «make a bridge» with the lower layer. We can do the following comments:

168

- The sides of the segments in the figure 6.5.2 are not radiating. Only the axial plane of the segments runs through the centre of the piece. This makes more difficult the merlons positioning (see further). It’s not possible to lean against a virtual surface! - In the figure 6.5.1, a side of each merlon is radiating, this makes easier the merlons positioning. - The aesthetic result in the figure 6.5.2 is quite appropriate. On the other hand, the result in the figure 6.5.1 may fail to come up to expectations, if the piece thickness (radial dimension of the segment) is great, but however, it is infrequent.

- Facing the classical disposition which follows, the left dispositions in both figures are not of great interest, except an intellectual one, or the exception of using segments which had not been cut at the right angle. - On the contrary, even if they are commonly little used the dispositions on the right side (merlons with parallel sides) can be included into a drawing. We will privilege then the one of the figure 6.5.1, to favour later the positioning of merlons, if we desire that all of them have the same position, but for a 2π/N rotation.

But I think that the following «classical» disposition is by far the most appropriate one, as well as regards the drawing, which becomes easier, as the positioning of segments and aesthetics. It fits to the grouped cut trunconic merlons

Group 3. Trapezoidal crenels AND merlons

If we wish to match only trapezoidal merlons and trapezoidal gaps, the corresponding drawing is easier to do than the previous ones, chiefly when we combine different angulations on one ring. All the sides indeed are radiating.

Fig.6.5.3 «Classical» disposition. Crenels and merlons are trapezoidal

I have to add no comment about this drawing which is «classical», but also the most «natural», and intuitive one.

Even if it is necessary, the drawing is not all. We shall now broach merlon gluing.

169

Merlons gluing. General remarks.

The drawing must anticipate a minimal sticking surface. Every segment is a bridge. The support length is equal to the half of the difference between the total length (merlon) and the span (crenel), as illustrated in the hereafter figure. It would be hazardous to reduce too much the gluing length, the minimum taking

place at about 4 mm.

Fig.6.5.4 Symmetrical bridging. The dissymmetrical bridging is possible; it allows a spiral effect.

Applying glue to merlons raises no problem, apart from protruding as little as possible over the parts remaining visible, the crenels. Positioning raises also no problem if we make the piece with mixed (don’t’ confuse with composite) discs cut in trunconic rings (the full disc may be a thin waste disc if we reverse the assembling sense of the piece), for in this case all the merlons are pre-positioned automatically. It’s the easy solution, limited to the trunconic works with band saw. Moreover, the choice of the mixed layer operates automatically bridging from a merlon to the other one through a full layer.

On the contrary, the positioning is not obvious when we have to glue separated merlons (trapezoidal merlons in most cases) by respecting in the same time the right angles and the distance to the centre. Several solutions were imagined by different people. All of them have good results, if we consider according to the splendid productions of the turners I mention in the chapter 9. All this does not prevent for me to have a viewpoint, and inform you of it during the following overview.

- Daisywheel-jig

The craving to make openwork came to me soon enough while I had read almost nothing about this subject, except about what I call further the «merlon-rest», removed right away as for me because one has to work on the lathe. In my defence, it is true that the books of the authors who developed this openwork technique were published not so long ago.

170

Right away, I found my way towards a jig I named «daisywheel» (marguerite) because of its shape.

I started with a N6 piece, then after a long interruption, I came to a N9 one, and I stopped at N12 before I had a preference for the «guillotine». Here is a photo which gets it talked about N12 daisywheel made in the process of execution.

Photo 6.5.5 Marguerite jig (daisywheel jig)

In order to make the task easier, we have to draw the circular centring marks and the radial positioning before cutting the «petals». A 1 cm gap between the circles is a sufficient precision. As regards the centring, we play on two couples of diametrically opposite and 90° shifted marks. .

Photo 6.5.6 Daisywheel presented on a ring intended to receive merlons.

171

Once centered and azimuth oriented, the daisywheel jig is kept in place thanks to a ballast, here steel log off cut. Merlons are glued between the «petals», and the radius is checked thanks to the marks remaining from the first drawn circles.

Photo 6.5.7 Merlons are glued

Gluing operation is fast, precise and comfortable. However, this method has its limits, quickly reached. The number of «petals» cannot be increased over and over; otherwise they would be too fragile at the roots. For the same reason, the width of the gaps can’t be reduced over and over. And chiefly, a new jig must be made again every time a parameter is modified. In spite of its attractiveness, this method is not worth the «guillotine».

- Disc-jig

That method is described in the book of Dennis Keeling (see chapter 9). Crenels shaped “triangulettes” are glued upon a full disc of a diameter at least as big as the one of the piece. If the crenels have parallel edges, rulers take the place of the “triangulettes”. We get so a jig which must be made again every time the parameters of the drawing are changed. It is in a way a variant of the «daisywheel - jig», but here the relationship stops.

The one alone advantage is that we are not forced by the weakness of the petal roots. But because of the presence of a disc which sustains the spacers, it’s not possible to be centred with the lower ring, nor glue the segments through the jig. How to use the «disc-jig»?

The trapezoidal segments are placed on the jig with the right radius, then the set is applied upon the already turned part, on the lathe, like a kind of a vertical «tarte Tatin» (upside down pie). The lathe operates the centring, the azimuth orientation

172 from a layer towards the other one, and the clamping. We wait for the glue to set and we start again. Double drawback: working on the lathe and in practice making a jig with every piece to be made. All things considered, I take the choice of the daisywheel-jig.

- Merlon-rest

Now we turn ourselves towards this grand master in this area, William Smith. This latter describes a method I gave the name of merlon-rest because the used accessory looks like a tool-rest. This accessory is easily depicted: a horizontal angle placed at the axis level of the lathe, in front position (perpendicular to the axis) and just at the edge of the previous layer upon which we have to glue merlons. So the angle is at fixed level from the workbench, the axis level of the lathe. It’s possible to fix it on a rest screwed on the workbench, or (lesser storage clutter and quicker setting up) upon a rod fitting with the banjo. The radiating edge of the segment to be glued is placed on the angle, which ensures due to the construction that this edge is rightly in the direction of the center (as a result, «classical» layout of the merlons) We set up on the angle a length stop against which we lean the segment in order to ensure the conformance with the drawing, we glue and we wait for the setting of the glue before turning the piece and going to the next segment. This 2π/N rotation can be made with the help of a dividing disc, which most of the time restricts the choice of N to 24, 12 or 8. In the other cases, a handmade dividing disc, made according to N or a multiple of N, dividing disc which is fixed either on the head-stock wheel, or on the chuck (which is immobilized during all the operations, like the lathe). I think this long method, segment after segment, with an immobilized lathe, can’t be recommended, even if it allowed for turners to make wonderful pieces.

- “Guillotine”

After the experience of the daisywheel-jig, I came to the following list of the requirements we have, in my opinion, to set ourselves to conceive an accessory allowing positioning and gluing in good conditions the merlons of an open layer:

- Working out of the lathe and under way piece vertical on its chuck, in order to have the gravity as an ally. - Universality towards the different drawing parameters - Easiness of the different adjustments.

At the same time, through the William Smith’s website (still him!) I found by chance an object the design of which was roughly corresponding to these requirements. The «Driskell Glue Up Jig», an accessory imagined by the turner Jim Driskell.

173

This accessory comprises :

- A stand in which a screw the thread of which corresponds to the thread of the headstock spindle is inserted. This screw swivels vertically. This assemblage determines a vertical rotation axis regarding the set piece + chuck that will be screwed on it. - A beam fixed on the stand. On it, a horizontal angle the vertical side of which passes by the previous rotation axis. - A thin disc drawn as an angle protractor, bolted on the screw and a pointer fixed on the edge of the stand. - A length stop clamped on the angle.

The whole looks like gallows, like in the westerns. On this same common architecture, I realised an accessory I gave the name «guillotine» because of its shape (you have the choice between hanging and beheading...!).

The differences between my jig and the Jim Driskell’s one are the following ones: - The rest of the angle slides on a double beam. This gives more stiffness as regards the twisting. Both beams are linked by the ends. The assembling with the stand is also easier to be made - Suppression of the screw, replaced by a hole the diameter of which corresponds to the diameter of the chuck bottom (threaded part). This reduces the height of the assemblage and so a centering error. This avoids the intervention of a metal turner. - Machining a lengthwise opening into the vertical side of the angle, in order to tighten a length stop tilting in accordance with the splay angle (useful and even necessary with the trunconic merlons). - Indexing every cm on the angle, from the vertical axis of the hole which receives the chuck. So transferring of the radius from the drawing is easier. - Inserting a lateral screw into the stand, this acts on the chuck bottom, to ensure the temporary rotation locking.

The device is completed by a «double sided» gluing of a dividing tape on the circumference of the driving waste disc, the diameter of which is at least equal to the chuck one. This tape may be for instance a plastic tape for strapping the parcels. The diameter of the waste disc is measured and multiplied by π. The result (perimeter) is divided by N, and this value is transferred N times on the tape. Beware: the transfer N times must be made by cumulating the measurements into the pocket calculator, with all the precision of the division result. We get the odd ranking layer indexes: 1, 3, 5…Between these indexes, with a distinguishing mark, the indexes of the even ranking layers are placed, generally in the middle of the previous indexes, and with a discrepancy if the bridging is not symmetrical, which is infrequent.

This azimuth dividing tape is precise and easy to use, with no error risk. This part of the system is the one alone which is not universal. The tape must be made again for each piece of different parameters. But its fashioning takes only a short time. An index is fixed on the stand in order to allow the rotation adjustment according to the marks on the glued tape. Making the «guillotine» is accessible, technically and financially, to every handyman.

174

Here is an overall photo, and photos of details:

Photo 6.5.8. Overview of the «guillotine»

Photo 6.5.9. Stand detail Photo 6.5.10. Centering handle detail

Photo 6.5.11. Adjustable stop detail Photo 6.5.12. Tape drawing

175

Instructions for use of the guillotine are the following ones:

- The piece under assembly is removed from the lathe, with its chuck. - It is placed directly on the stand, after raising the sliding shaft. - The shaft is pulled down on the top of the piece, that is to say on the base disc or on one of the previous merlons we choose according to the drawing. - We make the chosen mark corresponding to the index by rotating the piece, and we lock it with the screw on the stand. Azimuth (horizontal rotation) adjustment is completed. - A segment is blankly applied on the angle, which ensures a radiating side, passing through the center, or better the axis of the piece. The length stop is adjusted at the right distance and the right angle, and we lock it. So the segment is leaning against 3 sides and we can glue easily and precisely. We press our finger during a few seconds. We remove the potential glue surplus, and we may go on. - The rotation is released after the shaft is raised, we adjust it on the next mark, we lock again the rotation, and everything is ready for gluing the next segment, without tampering with the adjustment of the length stop until getting the complete layer. The piece is ready to go back to the lathe for the next intermediate turning (after sufficient hardening of the glue, of course).

In this manner, gluing of a merlon layer takes only few minutes. I see scarcely what we could improve as to the chosen principle from the moment when the segment to be glued is physically guided on THREE sides. Resorting to a laser could seem enticing, would not bring this easiness and this safety of the merlons positioning. Let your imagination wander, if the fancy takes you!

Here is an example of execution on a trunconic piece with a variable splaying including five woods: wenge, laburnum, cocobolo, maple, walnut.

Photo 6.5.13

The disc made of triangulettes through a paper sheet glued on a waste disc. The disc is cut by trunconic working with a band saw to get geometrically identical merlons which are easily plucked off. 176

Photo 6.5.14 The indexed tape is glued on the waste gripping disc with « double face tape».

Photo 6.5.15

“Guillotine” in action. The segments are glued after one another in record time. This guillotine is considerably more than enough sized as well by the diameter as by the height. Made by two blocks, a 1 meter high piece could not scare it. I afterwards improved the positioning handle by substituting the flat bar by an angle which bears a positioning stop. (photos 6.5.10 and 6.5.11)

177

Photo 6.5.16

“Guillotine” in action (continued). The segments are removed one after another from the ring block. We don’t run the risk of getting the colour wrong.

To see the finished piece, I named «Quintette», go to the chapter 8.7.

Intermediate turnings and hollowing

There are not great things to add to what was said in the previous chapter about rounding, surfacing and hollowing, except that we have to be still more careful and delicate when an open piece is turned. «Scything» cuts are necessary for the outlying upper part of the merlons layers, gouge handle down. Work at the axis level, tool rest adjusted therefore as close of the piece as possible.

178

7. Machining of the piece and its completion

7.1 Inner profiling or «hollowing»

In order to name the operation we talk about here, the shortest and the most imagined word «hollowing» may be used by extension. But it is more precise to use the word «inner profiling», and forget «inner turning» or «inner machining».

The present chapter concerns all the layered pieces. This layered turning technique allows in fact profiling the inside of the piece (the inner machining is assimilated more or less at the end of a hollowing) as its assembling proceeds, or making it with several blocks, put together after they are «hollowed». And it does not matter the layers are full or open, and the segments trunconic, trapezoidal or pyramidal. The following advices are the same.

In order to assemble the piece (or half of a piece in the case of closed shapes), we rounded partially, of necessity, the summits of each layer. This is a first series of partial turnings, operation made easier, but not taken out with the circular and trunconic segments.

It is possible, of course, to choose having finished assembling the piece before hollowing it. It is valid as regards a much flared bowl, but in most cases, it is better to take advantage of this godsend and hollow the piece part after part. This adds another series of more or less ended partial turnings

Shape continuity in the inside of a piece section

The question of the hollowing was already broached in the chapter 6.4, concerning tools handling. We have to return again to it, in order to speak of the shape continuity. When a single wood piece is hollowed, you start from the top, and you finish by getting down successive sections. It is the best manner to prevent putting out of shape the woods by their loss of moisture and the release of the inner constraints. The shape continuity is easily secured, by reference to the already turned piece, upon which we can press the gouge bevel, in French «talonner». Could I say “bevel rubbing”? In layered turning, the situation is reversed, for we start by the bottom, while going on to use the «pushed gouge» technique, for a smoother work and to avoid stripping causes. It is necessary to imagine the shape of the future upper part, instead of leaning against it.

179

The solution I apply is clarified by the following sample:

Fig.7.1.1 Hollowing steps (inner profiling) of a layered piece

On this drawing, the small black triangles show the rounding layer after layer, generally as well inside as outside. Hollowing step A is starting when the 4 first layers are glued. The inside of the layers 1 and 2 is finished, the layer 3 is trimmed, and the layer 4 is not touched. The step B is starting after the layer 7 gluing. We bring then to an end the layers 3 and 4. At the time of the step C, after the piece is entirely glued, the layers 5 to 8 are finished. The method consists in leaving systematically unfinished the two last glued layers. It is so possible to visualize what the upper layers will become after definitive inner turning, and secure the shape continuity, that is to say, a well-balanced progress of the curvature, with no stairs, no hollow, and no bump in the profile.

Save a little wood «in the event of», and make if necessary a few small final alterations, by leaning now on the upper part, bevel rubbing, as made in the case of a single wood piece.

180

Here is a sample of hollowing a section of a wholly open piece :

Photo 7.1.2 Example of partial hollowing of a big open bowl (see chapter 8.6). On condition that you have a light hand and use fitting and well sharpened tools, the merlons will hold out, including those of the upper layer which are exceptionally profiled inside, with no closing ring to support them. You can make it safer by applying packaging sticky tape outside the last layer.

The case of pieces made of several sections

The things become a little more intricate when we must hollow two sections of the same piece intended for being joined end to end. Once the two sections are glued, it will seldom be possible to rework the inner turning. A common minimum surface for gluing must also be saved, and so the diameters must not be too different. A slight flaw (stairs) is not serious if the piece is not open and if we can’t see the inner joining through its neck (photos 1.9 and 4.7.2). On the contrary, the matter becomes really complicated if we can see the joining through the neck or…if the piece is open (photo 1.11 for instance). Then the flaw has to be very small. We have so to be very precise in order to secure in the same time the equal length of the inner diameters of the two sections and the shape continuity. It is better to part these both operations if we want avoiding the machining (with lathe) of a three dimensional jig, which is possible but a little long and not necessarily more precise. Don’t forget that each section has its own driving chuck. This allows, if necessary, alterations on both segments to be joined end to end. As for me, I begin by checking that the both diameters have the same length, for this is the most visible flaw if it remains. In order to compare them I suggest three solutions:

- The caliper - A little thick flat rule (flatly laid) as long as the inner diameter, the ends of which are precisely rounded under the lapidary after marking with a caliper. 181

- A transparent plastic disc (thin Plexiglas for example) on which a circle at the right diameter is drawn. This one may vary slightly in regard with the circle of the drawing. This third solution is better, chiefly in the case of ending crenels over crenels. The same disc may be used many times. It is sufficient to draw a circle at the wanted radius. As regards the shape continuity, I suggest making a flat jig (edgewise positioned) which can go into the piece before finishing the turning. It is sufficient for the jig to enter 3 or 4 centimeters deep to estimate and adjust the shape continuity. The aim is for the inner profiles of the two sections to be at a tangent with the same straight line at the point of joining. This cardboard or Plexiglas jig, traced on the drawing, is fixed on the edge of a thin wooden ruler leaning against the edges of sections under process. It is sufficient to place it at the level of the axis and do it sliding until it contacts the wood in order to estimate the necessary machining alterations. The following picture clarifies what is preceding:

Fig.7.1.3 (RM) Check jig of the shape continuity between two sections.

Note that this kind of jig can be used to check that the two parts of a box are well matched aesthetically, as regards either layered turning or not. Generally, we make do for the junction to be made on a point where the tangent to the profile is in a parallel to the axis, which makes easier the problem.

The case of distortable pieces

Some pieces are too much distortable under the pressure of the tool, even the lightest one, from a certain number of layers, to be hollowed without the help of an accessory. The classic solution is also the best one: setting up a “roller- stabilizer” or “spindle steady”(“lunette” in French).This raises no problem if a full layer is placed at the right level, which is sure if: - the piece is not entirely open, of course - a full layer is planned as soon as the stage of the drawing - mixed layers are put together, as in the above example.

182

Photo 7.1.4 An example of “roller- stabilizer”, or “spindle steady”. See also photo 7.2.4 and chapter 8.8

On the other hand, the problem is wholly raised when the whole piece is open.

Gérard Bidou imagined a solution which demands foreseeing a waste disc with a diameter greater than the diameter of the layer to be «supported». This solution consists in passing through two 180° opposite crenels of the last but one already made ring, a cross bar with the ends which get beyond every side. The tips of this bar are bored in order to place two threaded rods which link it to the waste disc, in a parallel with the turning axis, outside the piece . A second cross bar is placed on the lower layer, at 90° of the first one, and completes the device. This ensures 4 support axial points. I add that if the crenels are too narrow, the cross bars may be replaced by metallic cleats, the linkage with the threaded rods being made by stirrups. So attractive it is, this solution presents a major drawback in my opinion: because of the cross bars it is not possible to return to the lower part of the piece, or to put the finishing touches for hollowing, or sanding it.

I prefer a solution which lets entirely free the inside of the piece or the section of a piece. I propose you the solution illustrated below.

Fig.7.1.5

183

Once we have chosen the place of the stabilizer, or spindle steady, tabs (4 or 6) are glued on the periphery of the piece, on the tangential sides of merlons of the same layer and opposite 2 by 2. Those tabs form kinds of fins which are bored in advance in order to be able to screw an extra outlying ring cut into medium (15 or 25 mm thick according to the wheels of the spindle steady). The inner cutting of this temporary ring can be made with a jigsaw, a scroll saw, or a troncoline. The precision is not very important. In order to slip the ring on, the between centres piece must be removed from the lathe of course. When screwing, take care of inserting wedges, if necessary, not to pull on the tabs.

This ring is later rounded outside, and the stabilizer can be placed. After hollowing and sanding the piece, this ring is unscrewed and the tabs sawed. The «Japanese» saw works marvellously with this kind of operation. The leftovers of tabs and glue are removed during the outside profiling, between centres.

The sketch A in the figure 7.1.5 represents a rectangular tab glued either on a trapezoidal merlon, or a pyramidal merlon. No problem with the trapezoidal one which has automatically a tangential flat side in a parallel to the lathe axis. The tab has so a radiating side perpendicular to the axis and the ring can be applied on it perfectly. If the layer is pyramidal, which is not to be precluded, the glued side of the tab is made with a tilting equal to the splay angle, for the ring to be laid flat at best when screwing.

The sketch B corresponds to circular and trunconic merlons. In the case of circular merlons, it is sufficient not to cut outside the segment, and the tab is made, already «glued»! With trunconic merlons, we have to provide 3 or 4 additional merlons (it’s possible as we are in open work) and to glue them on the right layer. They will match perfectly, except for the saw kerf thickness.

7.2 Outside profiling of the wholly assembled piece

Putting apart the much localized turnings for rounding layer after layer, the wholly assembled piece is outside rough from machining. We keep so as long as possible the maximum of glued surfaces between the layers.

There is almost no difference with a single wood piece except for two points: - The almost systematic presence of one waste disc or two, which must be removed and the mark of which eliminated from the piece. - A bigger weakness in the case of open work.

As regards trimming passages, which are very logically run from the top to the bottom (from the tail stock to the head stock, which allows keeping the foot with its biggest diameter as long as possible), we must remain watchful, for this kind of piece does not withstand stripping neither mechanically, nor aesthetically. We have only a too faintly thick wood for catching up the errors. 184

Advices concerning the tools made for hollowing remain valid: fitted and well sharpened tools. The passages must remain light. Don’t be eager. Many preparation and working hours come before this a little risked last stage, and they must not be lost by awkwardness or inattentiveness. In my opinion, I trim with a bowl gouge, I go on with a spindle gouge and I make a finishing passage with a double bevel (skew) chisel (kept horizontally at the axis level) only on the full parts. Two cases arise before profiling the outside: Either the piece, still glued on the waste disc, is stiff enough, so the machining operation may run till sanding with no other precaution, or, the set becomes warp under the tool pressure, and the help of an accessory which is fitted to every specific case is necessary. Most of the time, working between the centres is sufficient to see this operation through successfully.

Here you have some samples

Photo 7.2.1

This vase would be too high to be borne only by its bottom, on the left on the photo. The two sections which make it up are just glued with one another. The bottom waste disc is used as a drive. The neck waste disc is screwed with its faceplate on a specific turning point thanks’ to a threaded insert adapter (Thanks’ also to mister Oneway...). Held that way, the piece does not run the risk of getting away! It is perfectly stiffened.

This device can be replaced by a male friction drive chuck hollowed in its side towards the tailstock in order to be pulled on the turning point. Or still by a well fitted to the neck and perfectly centered friction drive chuck, held by the live center.

185

Photo 7.2.2

The same vase after profiling is just turned over to add the finishing touches to the bottom which has lost its faceplate. The bottom waste disc can now be removed. Later, it is the turn of the neck waste disc. The neck is sanded, unless you prefer turn the piece over an nth time, before removing the bottom waste disc which will be grabbed into a jaw chuck, and so one. Each in his own way.

Photo 7.2.3 A different manner to stiffen an assembly: a proportionate turned piece of wood grabbed on the specific turning point. A covering with embossed painter sticky tape is welcome. A rag stuffing may take the place of the turned piece of wood.

186

Photo 7.2.4 The piece is almost completed. The neck machining must receive the help of a spindle steady.

Photo 7.2.5 See chapter 4.1 and photo 4.1.13. A 2 layers piece: a bottom disc and only one pyramidal layer. The kind of grabbing allows machining the bottom in complete safety. The vase can then be made like a single wood piece.

187

Photo 7.2.6 A usual last machining: the suppression of the bottom waste disc, thanks to grabbing on a reworking faceplate.

7.3 – Sanding and finishing

Sanding a layered piece deserves to be dealt apart, although it is the final machining stage, the one that follows the profiling. Mixing of woods and openwork involve specifies in regard of single wood turning. Don’t forget we have made the choice of very dry woods, suited to gluing (so not very greasy), having a close hardness if we are mixing different woods. In spite of these precautions and in spite of the smallness of the elements put together, we have to expect light distortions due to the ambient moisture that the piece will suffer when moving , specially unavoidably from the workshop to a heated room. Those distortions result in slight (and even very slight) unevenness that very often the hand only feels. If you are a demanding «purist», ideal is sanding the piece, keep it during a fortnight in its future surroundings, and then bring it back to the workshop in order to rework sanding before applying the finishing coats. I confess I have not this patience...

We have as far as possible to take notice, at the time of choosing them, of the colour change of several woods under the light effect. This is how the beautiful red padouk while worked, will grow dark and turn brown. The laburnum, this beautiful tree which makes clusters of so poisonous yellow flowers will turn from greenish to a pretty dark chestnut brown. In the same time, it is necessary to take into account the colour changes which ensue predictably from applying some finishing agent. Preparatory tests upon samples are welcome. These all things considered minor warnings being made, let us look through in the order of precedence over the four usual operations that follow profiling, which are sometimes as long as the operations from rough wood to the profiled piece: sanding and dust removing, buffing, varnishing, polishing and glazing.

188

Sanding and dust removing

Two snags we do not meet usually with a single wood piece: - The hardness differences of the woods lead to the hollowing of the soft woods, if we press too much and the profile is affected. That’s speaking in favor of sanding «lathe off». The operation gets so better under control. - The open pieces. Sanding «lathe on» leads unavoidably to round the edges of the merlons, and this is to be judged enormously by the finished piece. Only one solution: sanding «lathe off».

Everything prompts sanding «lathe off», except in one case: the outside sanding of a non-open piece. It is possible so to use the following technique: applying over a great length an abrasive belt stretched between your both hands, a little diagonally in regard with the circumference of the worked area. But be careful even not to hollow soft woods.

After having tested a great number of sanders, rotating, thrown of center, vibrating ones...I use only one technique, valid for all the cases I met, even the most difficult ones, as well inside as outside of the piece. I made adaptation units on a mini variable speed grinder you can see the above photo:

Photo 7.3.1 The mini grinder used as a sander and its «home-made» adaptation devices

The axis of this grinder has two threads - a female thread Ø4 mm which allows inserting directly a flat buffer as the one in the bottom on the left. - A male thread which allows screwing two Ø3,5 mm or Ø6 mm trade small chucks which themselves allow grabbing «handmade» buffers (in the bottom on the right of the photo).

189

Apart from an accessibility problem, I have rather the chuck solution which allows changing a buffer in no time at all, these small chucks being clamped by hand. I make the rigid part of the devices on the lathe in order that the buffers are well centred and balanced, with a metallic rod (aluminium) inserted and glued into a piece of wood. Practically all the buffers are fitted with foam (as used with heating pipes, while waiting to find better), which supports a male (fitted with points) «Velcro» disc. Upon this I fix a female Velcro disc which receives the abrasive disc. I make all these little discs (20 and 30 mm) with a hole-cutter. The Velcro ones in a 100 mm wide tape we can find in every good notions store. I use two kinds of abrasives (100mm wide tapes): - Either directly open abrasive tape which holds well enough on the male Velcro. - Or abrasive cloth glued on the female Velcro (sold in the same time than the male one). With the second solution we have a better resistance with use. The rotation speed is about 10.000 revolutions a minute with Ø20 mm discs and 7000 revolutions with Ø30 mm ones. This big speed allows limiting the abrasive grain range from 60 to 320. Most of the time, I am satisfied with 4 grains: 60, 120, 180, 320. For these gluing, I only use neoprene glue, which has the merit of keeping suppleness after drying.

Bearing in mind the big easiness of machining the rests, and the quickness of passing to one another, I find more profitable to have one per grain, which handles carefully putting together with a Velcro. Moreover, the grain can have a mark over every rest. And this avoids confusions. Rests and abrasive discs are placed into the right socket when changing at every time into a box of the following kind:

Photo 7.3.2 Rests and abrasive discs assortment. One cell a grit.

190

If he piece is not open, the sanding is finished after passing under steel wool. When the piece is open, I get a good effect by holding the disc in contact with the piece, using merlons in order to zigzag into one another, as a child playing hopscotch. A difficulty arises when the dust of a dark wood is settled into the pores of a light colored wood. Using light colored woods with a dense texture (boxwood, holly, lemon tree …) which are difficult to be polluted is the first recipe fitting this problem. The second one consists in finishing the sanding, after a first thorough dust removal, by passing under a Ø 20 mm 240 or 320 grit very clean grinder disc, and treating only the light colored merlons. We get a bit the effect of a rubber.

The sanding operation is made of course under vacuum. A regular dust removing with a brush is advisable, so to observe the progress. Frequently passing to a thinner grain brings to light a recalcitrant scratch, and we are obliged to turn back to a bigger grain. It’s possible to make use of this «scratch revealer» and start with a thin grain: the flaws to be handled with a big grain (or even sometimes by an advisable scraping) will be even more visible.

Sanding is ending by a compulsory careful dust removing, first with a brush lathe on, then with compressed air and blowing device. If not, wood dust and steel wool particles would be taken back by the finishing products and removed later.

Buffing

We may consider that a piece is «buffed» from the time when it is sanded to 800 grain if we pass by hand the abrasive and to the 400 grain if we use high speed grinder. But we get quickly an even better result if we work the piece with polishing paste, and it would be real shame to leave this step.

I use only two pastes: a brown one for the woods of a mean or dark tone and a white one for the light colored woods, for the brown one tints them. Applying is made in three manners:

1° we put the paste by rubbing the «loaf» (paste block) over the piece, lathe at high speed, and we buff with a tight enough pressed cotton pad. This of course involves that the piece is not open.

2° we grab on the lathe a «friction piece»( “frotte” in French), cotton discs piled on an axis. Lathe in rotation, we put the paste by applying the loaf on the friction piece. Without stopping the lathe we apply the timber on the friction piece. It’s so possible to handle only the accessible areas. We have to take the precaution of covering the bed of the lathe with rags, in case the timber would hit it. Here is a sample of this kind of construction:

191

Photo 7.3.3 A “friction piece” fixed on the lathe headstock . 3° we fix the «frotte» (friction piece) on the tip of a resistant flexible shaft (a cord in a sheath). The first price of the trade flexible shafts does not resist long! We load the paste on the friction piece by applying it strongly on the loaf, kept in the other hand (as for me I lean the loaf against my thigh). While taking care not to tie the cord, which wears it quickly, we apply the friction piece on the timber remaining fixed on the lathe, and we choose according to the result got after a few tests, among the rotation of the alone friction piece or its combination with the lathe’s one.

Here is an example of such a fixture, from a drill. If we can have one, the specialised engine-blocks hanging possibly over the lathe are better worth.

Photo 7.3.4 Buffing with a «flexible shaft». Example of a drill fixed on the banjo.

192

Sealing, varnishing

Once the delicate sanding or the buffing is completed, we can stop here, and accept that the wood will remain exposed to all the ravages to come. We can make a pace ahead as regards its safety or its aesthetics, applying one or other of the oils we choose, which will improve its water resistance, make it a little less dull, and bring out veining and colors. We have nevertheless to admit that the pieces ensuing from layered turning are rather sophisticated and require consequently a carefully done finish. That’s at least my opinion. You have certainly your own array of products, of wonder recipes and far is it from me to have the pretentiousness of diverting you from them. As for me, after a few more or less successful tests, for the time being I confine me to two finishes (I progress, the products progress, nothing’s frozen):

1° Spray varnish for the open pieces, because it is fast drying, «it makes its way everywhere» into the slightest corner, no tool is to be cleaned after the spray can is closed, it dries quickly. I prefer when I can find it the metal varnish, more laden with resin. Even if I repeat myself, don’t forget you have to remove dust carefully from all corners and nooks. The potential varnish surpluses, chiefly in the corners, must be removed very quickly, with a fine brush, before the varnish is dried in order for it to have time for tightening. I use in order to spray the varnish as finely and regularly as possible a potter accessory the French name of which is «tourne» (rotary table), a lathe with a vertical axis, very basic and moved by hand. At this stage, if we respect the untouchable rule, every griping mark must be vanished from the timber, hence the need of a movable rest which cannot be the lathe anymore. It is much more practical than turning around the timber ...!.

I made my «tourne» with a record-deck of the «sixties». Here it is:

Photos 7.3.5 et 7.3.6

A «tourne». On the left, the stand made of turned wood and bored on demand, the movement of the record player, and the record deck stained by the successive varnishing operations.

193

We must not, above all, carry on spraying the varnish, if not we may have drips which appear not necessarily immediately and are later pulled out with great difficulty. Multiplying thin coats is better. The «tourne» is in this case preciously helping. Good lightings are essential.

- 2° The second solution I use is applying varnish by hand. We may use a brush or a piece of fluff-less rag. The cellulosed varnish gives good results and dries quickly, sometimes even too much. It’s up to you to choose the number of coats.

The finishing may be stopped there. If you find the gloss is too dazzling, a very light “sanding” (“égrenage” in French) with steel wool can soften it much.

If you varnish on the lathe, don’t forget shielding the bed from possible drips and products spatters.

Polishing and glazing

The «varnishing-polishing» is a very classical finishing, much estimated by a large majority of the people ... and turners. It is unhappily seldom possible to apply it on an open piece.

Once the varnish applied, delicately sanded, with dust removed, the timber is covered with a thin coat of wax we have to let dry during less or more time according to its composition. I use the «microcrystalline wax» which has the double merit of drying quickly and hardening enough in order for the piece not to be «sticky».

Carnauba wax gives very good results, but on the condition that the piece is sturdy enough to withstand the efforts needed to apply it. It is melting under overheating caused by the friction. Working with a «slight hand» is not possible.

After the polishing comes the glazing. All the scratches, even the thinnest ones, must disappear thanks to the glazing. Lathe on, when it’s possible and if the piece is not open, we apply a wool rag.

If it is not possible, we reverse our gesture as when sanding. We find again the «frotte» a very useful accessory, but now made of thin cotton, or flannel. Still as when sanding, either we present the piece over a «frotte» moved by the lathe, or we present over the timber (wedged or in motion) a «frotte» moved by a flexible shaft.

The «frotte» (cotton discs) fixed on the lathe is interesting for its diameter has no limit as when fixed on a flexible shaft. This allows getting good results. It is possible to «harden» or «loosen up» at will the frotte, by playing with the rotation speed and the ensuing centrifugal force. We glaze bigger areas in the same time. A great frotte (cotton discs) is ideal to glaze a broad splayed bowl.

194

Here is a «handmade» sample, from cotton discs bought at a marble work supplier and a “goblet” chuck I condemned to this use.

Photo 7.3.7 Example of glazing cotton discs (“frotte” in French). It is necessary to take it away as far as possible from the spindle nose to free the movements of the timber we are applying. Don’t forget wrapping up the lathe bed.

When we meet complicated cases, and notably as regards openwork, we may resort to a small felt disc fixed on a mini angle grinder you can see in the above photo 7.3.1, by sinking a Ø4 large headed metal screw in the felt. The high rotation speed will correct the small diameter of the disc.

We may gather together several felt and cotton discs on the same threaded rod we take on the lathe between centres. This kind of assemblage «on buffing bench» is not very secure. It was already a source of accidents with a too small diameter rod, badly held side towards headstock. But chiefly it limits the positions of the piece we are working with, much more than the «faceplate» assemblage I use.

195

8. Examples of realizations

8.1 And now let’s go !

After learning the different technical basic stages which are just explained and which I assume are acquired, we can go the creation phase. With a minimal success warranty thanks to this learning, we shall try to materialize an idea, to satisfy an aesthetic impulse.

First we start with sketches.

.A dialogue, or rather a discussion, is being developed between the available woods, the choice of the shape, of drawing and colors, the choice of the method, the different technical constraints, and... what we cannot find in the battery of the basic techniques, what we will have to think up or fit.

After this, the necessary drawing may be made, the woods chosen, then lovingly machined, assembled, shaped, buffed, varnished.

The finished piece is a star. It passes in the posing session before the photographers ...till the next piece will overshadow it.

Pictures of finished pieces, made according to the main methods I suggested you were shown in the introduction, to make «your mouth watered».

This present chapter has no other aim than giving you the desire to go as far as possible towards that direction, by illustrating for the best the different methods under the «step-by-step» form at the most reduced by the phases improved in the process of this manual. Hence the choice of the pieces, not necessarily around aesthetics. My comments are limited to bring out what is specific to the considered piece, or the tricks I did not yet disclose.

196

8.2 «L’Ecossaise (Scottish)»

Trunconic works are very attractive. And trunconic works with the troncoline even more. Here is a very simple example regarding its design and its realization. As for the results, I let you deem... The used woods are wenge, wild cherry, padouk, maple and bubinga.

The sketch of the piece profile. It does not matter to know the numerical value of the cutting angles, which are taken down directly from the drawing with a «Plexiglas flanged bevel square ». See photos4.1.7 and4.1.8

Gluing the sketch of the base disc on a covered in paper waste disc

197

The base disc is first basically rounded with a gouge

The surface refining with a bowl gouge (stiff bevel) is completed by a scraping with double bevel chisel, presented horizontally at the level of the axis (not as the photo).

The surfacing on which a good layers gluing is depending, is perfected on a sanding table. We note the circular mark made by the translating movements of the table on the bench in order to improve the sanding and avoid mucking up abrasive.

198

The troncoline in action, after the different diameters are drawn according to the drawing. The angle of the swivelling stand (parallel to the tool) is adjusted thanks to the flanged bevel square.

Rings are plucked off with a kitchen knife, progressing by small strokes all over the periphery.

The lower waste disc is glued on the disc central part remained in place. This waste disc is then rounded, and this ensures a perfect centering.

199

The lower set was plucked off from the initial waste disc. Two rings were glued. The inner profiling may start.

The almost finished piece is parted from the lower waste disc, and then gripped again in order to complete its achievement.

The piece is finished after five layers are « climbed up ». Even not out of breath!

200

8.3 «Les Deux Amar» (Two « amar »)

A kind of homage paid to a great family of the circus (AMAR Circus). Why the «Les deux Amar» ? Because the woods I used are amaranth and amarello. A blend of trunconic and trapezoidal works. The base disc, which will be cut with the troncoline, is an assembly of identical square battens cut from 2 chosen woods of high contrast. The neck is a ring of trapezoidal segments inserted between small plates. Let’s note that a ring made of trapezoidal segments is «servant» of the layered turning. It is found again in many pieces.

The waste disc may be used several times. This one keeps on its back old troncoline wounds.

The waste disc is covered in paper. Newspaper, typing paper… The vinyl glue must simply not go through the paper. I draw two perpendicular lines after locating the center on the lathe.

The wood is planed at the right thickness, sawed with the circular saw, then worked again with the jointer (while keeping its adjustment) to trim the sides of the square battens. Variant: mark and then respect when gluing the direction of the sawed sides, without planning them.

201

Starting the base disc assembling.

Oh! What a pretty pie! We should like to eat it. Note the direction of the square battens, unfavourable for working on the troncoline, but favourable once reversed for turning. Indeed the face we see here is underneath when gluing after cutting in rings

The disc is rounded with the gouge, and then covered with chalk in order to check the surfacing.

202

After cutting the trapezoidal segments, let’s glue the upper ring in four parts. The joining alterations with the disc sander are made on the segments, not on the small plates.

The last trunconic layer is cleaned and surfaced before gluing the upper trapezoidal ring.

The piece is much splayed. This time the inner profiling is made in one time. This avoids every junction problem of successive sections.

203

Without removing it, the piece is profiled outside to the base. It is better so providing a thick waste driving disc. The work is made easier by a rotation on the bench of the driving headstock.

The piece is almost finished, sanded, varnished, and polished. I remove it with a saw from the waste disc. At this stage I don’t accept to take the risk of removing it with a parting tool.

After a finishing phase of the base on a reworking faceplate , here is the completed piece.

204

8.4 «Riemann»

Here is a new sample of wedding between amaranth and amarello (Do you know the mathematician Riemann?). A partitioned bowl ensuing from the pyramidal method. In the trapezoidal working, the same shape and the same drawing would have required either multiplying the number of layers (influence over the aesthetics), or agreeing to have very high layers with a great loss of wood. This piece is made up of: - 2 full discs for the base and the neck - 3 trapezoidal intermediate thin N8 amaranth rings - 3 pyramidal composite segments N16 rings, with small amaranth abutted plates

A secured manner for cutting thin strips with a circular saw thanks to a graft of a broader board which allows pushing sideways instead of pushing between blade and guide. We meet often battens machining when layered turning.

Levelling of a board jut on a pyramidal segment. We must be careful not to damage the segment which was machined precisely. Check also that the machined side and the stay side are built well orthogonally. (The stay side is radiating, and its plane passes by the axis. It is so perpendicular to the machined plane that follows a crosswise cut of the piece, perpendicular to the piece, QED)

205

Gluing a ring of trapezoidal segments on a full disc used as a fitting drawing already grabbed on a faceplate chuck. The centring is so secured. This ring will be the bottom of the lower section.

Gluing pyramidal composite segments of a N16 ring, first in twos, then in fours, in order to get quarters of a ring, compulsory stage before slight alteration with the disc sander. The “stringeons” are very useful as they avoid a boring holding up.

Checking the squareness and the alignment of a half ring on the guide of the jointer. The quarters of rings were checked on the three dimensional square.

206

The three pyramidal rings of the piece are glued, ready to be worked after one another on the lathe for a partial rounding and a surfacing.

Compulsory passing of a pyramidal ring on the reworking faceplate for a partial turning: rounding and surfacing the seen side which is first glued (smallest diameter).

The preparation of the low amaranth ring for the gluing of the lower pyramidal ring.

207

The gluing of the higher part of the piece. Note the particular assembling side towards tailstock which allows keeping a very good centring after the general reversal that will follow.

Checking on an aluminium ruler a N 8 amaranth intermediate half ring before gluing the complementary one.

Inner profiling of the lower part of the timber and surfacing the intermediate amaranth ring.

208

Inner profiling of the lower section

Gluing the two sections out of the lathe. Everything is good to squeeze the set, even a stone! Both faceplates chucks are still here.

Outside profiling of the set. The neck is on the left. Take care not to get lost among the numerous successive reversals.

209

It’s time now to free the vase neck side.

Machining of the neck only initiated at the time of hollowing. The piece and the faceplate grabbing are stiff enough so that a spindle steady is not necessary.

The completed piece. Finishing: cellulose varnish, then microcrystalline wax.

210

8.5 «Meandros»

To adorn a turned piece, how not to think of a frieze around it? And we say «frieze», how not to think to a «Greek» one, as those which adorn the magnificent monuments of Greece, this beautiful country? That’s what I intended by making a bowl I named, as by chance... «Meandros» (I let you to translate). The woods I chose are bubinga, a little sapwood of which I kept, carob tree sapwood (a light colored finely textured wood, its heart is pink with grey shades) and rosewood verging on purple, with a very fine texture also. The piece includes: - 1 full disc forming a very short stem - 1 N8 triangulettes plank making the bottom - 2 trapezoidal segments N12 rings, fitted around: - 1 composite segments N44 ring making a Greek frieze - 1 upper N12 ring forming the rim. The a little strange choice of N44 comes from the approximate division of the perimeter (ensuing from the choice of a diameter) by the width of the composite segment, equal to the (chosen) height of the same segment.

The starting material: a N8 bottom disc, the stem disc on the chuck.

First machining stage of the composite segments making the Greek frieze. Only the usable parts of the rosewood batten are donned in a carob sapwood plate (in spite of the rosewood firmness, the worms went here).

211

Cutting the heart of the composite segments with a miter saw. Reversal method, the blade is vertical, the plate underneath, then on top, this gives...geometrically identical segments.

Gluing one after the other on the second plate which lines every composite segment. The skew side is turned towards the ceiling, but towards two different directions in accordance with the two blocks. We need 22 «plate to the left» segments and 22 «plate to right» segments that will be parted with a hand saw. A plastic sheet inserted between two consecutive segments keeps the place of a Japanese saw, very narrow at sawing.

Disc sander levelling of the slight jut ensuing from the preceding sawing. Is the segment too small or the finger too big?

212

After its assembly, the bottom plank is glued on the basis. A thin framer spike first stuck into the center of the stem disc runs through it. So the centering is secured. Note the cross ornamental effect ensuing from cutting the plank segments by reversal. The small central flaw ensuing from joining the tips of the triangulettes is then filled with a trunnion.

Gluing the first trapezoidal ring on the plank one third after another. The joints between N8 and N12 are crossed for the best.

Assembling of the N44 ring on a drawing. In this case no question of gluing directly on the piece. We must take advantage of the suppleness of the set not to have to correct the closing segment. Double faced support catches glued on the periphery are very useful.

213

Gluing composite segments ring after passing the lower side on the sanding table (on top of the picture, on the bench) The lower part of the piece was first rounded. The centering is made «at a guess» while assessing the outlying juts. It is the same thing about the two next rings which complete the piece.

Detail of the Greek frieze. Rosewood and carub sapwood.

The completed bowl «Meandros». I chose to move away from the classical shapes ensuing from pottery in order to highlight better the Greek frieze visible outside as inside

214

8.6 « Tête Bêche » (Head to foot)

This piece has only, in my opinion, a didactic value. Its shape is poor, as the choice of the woods, limited to kiln dried wild cherry I got very cheaply by the neighbouring sawyer. I wanted to make a big openwork vessel in a closed shape, including two almost identical head to foot glued sections, by testing the combination of the two methods: - sawing groups of merlons, in trunconic work, with a band saw, splay angle unchanging; - setting up merlons with a «marguerite» (daisy wheel). The test was convincing as regards the implementation easiness and execution time.

As wanted, the drawing is very simple.

The two partial discs, one a section, are ready to be cut with a band saw. A central graft allows the boring which receives the rotation metallic catch stuck into the sled. The paper is used here between the triangulettes. It involves cleaning the merlons radiating faces. To be compared with gluing on a thin waste disc.

215

No problem with band saw cutting. The sled slant is constant. The setting of each radius is used twice (two discs). The «cutting» operation is very speedy. The group of all the units ready to be assembled are the subject of the picture 5.5.4

Positioning the merlons with the daisy wheel is a child’s play.

Both sections are glued simultaneously

216

The upper section receives the joining central ring. Then it is profiled, sanded and varnished inside before it comes out of reach.

Profiling the inside of the lower section. With a light hand, a little skill and well- fitting and well sharpened tools, profiling and surfacing of the upper merlons raises no real problem The inside is later sanded and varnished.

Both sections were butted. The foot faceplate chuck is removed. The centering of the waste foot must be carefully checked.

217

The piece is turned over. The waste foot is taken hold into a jaw chuck. The waste headstock disc is removed, and then converted into a print and placed side towards tailstock. The outside profiling is ready to be completed. Sanding is following.

Machining of the foot, lightly cupped of course, after removing the waste disc. A very short tool rest, cut into a big heating pipe, allows coming near the work area.

The completed spray varnished piece.

218

8.7 «Quintette» (Quintet)

The different options chosen for this bowl are the following ones: - wedding of 5 different woods. Clockwise: wenge, laburnum, maple, cocobolo, walnut; - classical openwork, with positioning on «guillotine»; - trunconic work, with grouped cutting with a band saw; - 5 layers of merlons, a foot disc and an upper ring. The rim is a cocobolo ring. (See also the pictures 6.5.13 to 6.5.16)

The basis disc is ready for cutting. The triangulettes have been cut by the very flexible back and forth method, hence their outside shape (non tangential cutting and unequal lengths). They are simply placed side to side, positioned on a central nail, glued (with inserted paper) on a waste disc. The side we see here does not need to be surfaced straightaway because it becomes the lower side of the glued layer. This method may be recommended.

The centering of the disc when cutting will depend on this hollowing (6 mm) positioned for the best at the merge point of the triangulettes tips.

219

Start of cutting with a band saw, waste disc on top. So the radius (The smallest one) may be taken down from the drawing without worrying about the thickness of the waste disc.

Working with the guillotine in order to glue the “triangulette” shaped bottom merlons, rested against a 6 mm central trunnion. To every line of the index tape glued on the waste disc a merlon corresponds. The paper and glue stained side is cleaned and surfaced on the lathe, in order to receive the following layer.

The piece is completed. It is in the sun, and it’s not very good for its health!

220

8.7 «Extra» and «Intro» vases

This manual would be unfinished, as far as it could be complete, or rather «much unfinished» if I did not present you an example of openwork from mixed discs. As I wanted to try this technique which was only in my imagination, I made two vases from three identical discs. An open vase I name «Extra» (from extraverti i.e. extroverted) and a closed vase I name naturally «Intro».

The woods I used are rosewood and kiln dried wild cherry. In the same open layer, small merlons alternate with bigger ones.

The necessary material in order to build composite discs of both vases is ready. Wild cherry triangulettes to make N8 discs, and rosewood to make the merlons.

The circular segments scribing of the median rings of «Intro». An example yet of mixing several methods in making the same piece.

221

A composite disc prepared to be cut in trunconic work with a band saw. Every open layer includes 8 big triangulettes and 8 small ones. The joints are crossed with those of the full layer. The guillotine use is not necessary to position the triangulettes. The joints of the N8 full layer and its center are used as indexes. The removable part where the saw blade passes includes 1 triangulette of the full layer and 3 ones of the open layer.

The median ring of «Intro» includes 3 layers of circular (machined with band saw) segments.

Every composite disc is completed by its removable part held by adhesive tape, reversed, and then bored in order to receive the rotation dowel of the sled. The side we see here will become the underside of the composite layers in the piece.

222

Set of the elements of the two vases before cutting the mixed rings.

Cutting mixed rings. The removable part is held by adhesive tape, after inserting the blade into the main part.

Test assembly of «Intro». No layer is glued.

223

Blank test assembly of «Extra». We are not far from the final shape. A big layer height allows slimness of the piece.

Hollowing of the bottom of one of the two vases. The junction of the triangulettes tips is provided by inserting a central trunnion.

Inner profiling of the 2 upper layers of «Intro» grabbed glued on a waste disc. Surfacing the merlons which will receive the next layer. Note the blue chalk line in order to test the job.

224

Spray varnishing, in one time only, of «Extra», open shaped, and so accessible. The vase is placed on a «tourne», a potter’s device. See photos 7.3.5 and 7.3.6.

«Intro» is completed. The shape asks for improvements, but the technique is serious.

225

9. Appendix

Explanations about some words and abbreviations

Word or Explanation abbreviation banjo Unit of a lathe which slides on the bench and gets the rod of the tool rest. Named also saddle. cos Read cosines. See «sin». crenel Free space between two merlons in an open layer machining Combination of machining stages of an object or part of an object, from trimming to sanding included. merlon Full element in an open layer, between two crenels radiating We can also use the word «radial» : which passes through the center or the axis of the piece sin Read «sine». Sinus. In a right angle triangle, we choose one among both acute angles. Its «sine» is the ratio between the opposite side and the hypotenuse. Its «cosine» is the ratio between its adjacent side and the hypotenuse. The “tg” (read tangent) is the ratio between the opposite side and the adjacent one. stringeon Closed arc of the circle shaped clamp, with two sharp ends. (personal new word) tangent At a point of a curve, its tangent is the straight line which comes locally closer to it. The tangent at a circle is perpendicular to its radius which passes by the contact point. No mixing with «tg» (See sin and tg). tangential Perpendicular section to a radiating cut tg Read «tangent». See «sin». Don’t confuse this ratio with the straight line tangent to a curve. to level To take out every protrusion of an element compared to another one by sawing, planning or sanding. to outline To cut approximately a curved shape by following a broken line similar to the trace. to plane See «to surface» to profile Give the final shape to surface Remove every roughness from a surface and make it plane. We can tell also plane down to trim Stage of machining before profiling triangoline Accessory making easier the machining of triangles and trapezoids. The (personal new triangoline A is used with a circular saw, the B one with a miter saw and word) the C one with a disc sander. triangulette Flat shape inscribed in a triangle and being similar to it. (personal new word) troncoline Cutting accessory of trunconic rings on the lathe. (personal new word) tourne (French) Small vertical lathe with no motor, on which the potter puts the piece to make finishing touches: light turning, painting an edging on the circumference

226

9.2 Bibliography. Internet

You will be surely much interested and even keen in reading the following books which inspired my thought, my researches and lead partially me to write this manual about layered turning:

2002 “Segmented wood turning”, by William Smith, Shiffer Publishing, USA

2003 “Segmented turning, a complete guide”, by Ron Hampton, GMC Publications, United Kingdom

2004 “Woodturning with Ray Allen, a master’s designs and techniques for segmented bowls and vessels”, by Dale L. Nish, Fox Chapel Publishing

2005 “The art of segmented wood turning, a step-by-step guide” , by Malcom Tibbetts Linden Publishing USA

2005 “Fabulous turned-wood projects”, by John Hiebert, Harm Hazeu, Tim Bergen, Henry Bergen

2009 “Wooden bowls from the scroll saw” by Carole Rothman Fox Chapel Publishing

2012 “ Segmented Turning – A practical guide “, by Dennis Keeling, GMC Publications, United Kingdom

I can only advise you to complete your information by doing multiple trips through the web. I don’t list you addresses, for in this matter there are many and quick developments. You have only to type the magic word «woodturning» and a marvellous world will be open to you.

227

Woodturning : Layered turning by Raymond Molinari

From my first steps into woodturning, I wished to make an open piece, and I invented a method to make it, combining a piling of segments and their positioning thanks to an original jig (the «marguerite», or daisy wheel)

After an interlude of a few years, this craving came back to me at the same time as I discovered in English editions books (under the restrictive word «segmented turning») wonderful polychrome pieces made according to the technique I named layered turning, technique the principle of which can be described simply: piling wood layers by gluing and turning them gradually or possibly at the end of gluing.

It came to me that the information given in the above books was incomplete. I felt the need of going further towards theoretical studies, then imagining and setting up machining and assembling techniques of the different elements included in a piece.

I have no pretentiousness of teaching you how to make pretty layered pieces. With this manual, I would like to share my experiences and to avoid you needless tests which would lead to dead ends, while making your work easier. Feel free to be critical of my solutions, to improve them,...and to find new ones!

This book is not an end, but an invitation for creation. It is not a «step by step» method leading to a particular piece, but to a set of techniques used in the layered turning. An intellectual approach which invites you to pass from theory to practice by improving what is suggested and incidentally imagining tools likely to make your work easier and more precise. I wish that this manual will be for you the starting point, or the link, towards the creativeness (and the complexity) of the layered turning and towards all the splendid achievements it allows and remain to be discovered, in spite of the research already fulfilled by «aficionados» in the whole world.

21 december 2016

228