By GEOMETER Be Drilled in the Angle Iron for Screws and Nuts to Be Used

SHAFT and BOSS FITTINGS

ECURING components to shafts are casehardened by heating to red, and spindles, to ensure posi- soaking in casehardening compound, S tive drive, is a problem that reheating, and quenching in water. can be solved in various ways, Before the shaft is removed from the chuck, a faint line is scribed where according to the size of the parts the flats will end; and two diametric- and the duty they perform. Keys, ally opposite lines are scribed hori- splines, tapers are chosen when zontally, using the scribing block at heavy twisting will occur, as on centre height, or the chuck jaws for flywheels, pulleys and gears for spacing. To locate the shaft in the power transmission; while for light jig, each line in turn is brought flush duty, grubscrews and cross pins to one side of the step, and the suffice. circumferential line to the shoulder. Slotting the boss of a handwheel For intermediate duty, squares and or knob can be done with it mounted flats are often used, particularly on on the top slide (in the lack of a such parts as handwheels, knobs and vertical slide), and using an end mill levers-although these fittings have a in the chuck. If work is finished general application and may be used except for the slotting, a set-up can for drive to small gears, cutters, and be made on angle iron, B. This is so forth. squared across the lathe, packed if Sometimes, the problem of fitting necessary to bring its face vertical, a small handwheel or knob can be and held by the tool clamp. Running a drill in the chuck, drill a plug hole to locate the wheel, which is clamped -though if it has holes, others can By GEOMETER be drilled in the angle iron for screws and nuts to be used. If the wheel or knob is still on its stock material, an alternative top solved by tapping its boss, screwing slide setting can be made with a built- it up to a shoulder on the shaft, and up angle plate, C. Two pieces of true fitting a locknut outside, Al. It looks rectangular mild steel are joined by like a prototypc wheel or knob on a countersunk screws. The working squared shaft; but if it is a fitting on face is also drilled and tapped for which some force must be used, the clamping studs, and is set parallel reduced diameter (core diameter of with the lathe axis. In preparatory the thread) introduces a, possible work, the boss of the wheel is drilled; weakness. This can be avoided by then the opposite end of the material using a shaft with flats and slotting, is centred for a set-up at centre or by broaching the boss to suit. height, D. For either fitting, the shaft is When a vertical slide is available. shouldered in turning, and has a nut parallel flats on shafts can be milled at the end, and pair of diametrically from a set-up in two blocks, E. These opposite flats, produced by filing or are drilled for countersunk gripping milling. When they are on the larger screws. Being parallel, they go to the diameter of the shaft A2, the rear of slide first one way and then the other. the boss is slotted to engage them; Each time, they are set vertically and when they are on the smaller from a pair of stepped plugs in a tee- diameter, A3, the boss is bored smaller slot-fixed by grubscrews. at the end and flats are produced by Broaching of flats in a boss, A3, broaching. is done by pressing a silver steel In tiling flats on a shaft. control broach through it. The tool blank of depth- and angular location is has two diameters, like the boss, ensured by a jig, A4. Two mild steel joined by a taper in which steps are blocks are drilled at the centre line machined for teeth, F. Flats are filed to make clamps for holding the shaft. to the ‘smaller diameter, and the teeth A step is sawn and carefully filed- are extended down the sides by filing. checking by micrometer-which will On being cut off, the tool is hardened give the depth of flat. Then the blocks and tempered to dark straw. lXl 5 JANUARY 1961 7 MODEL ENGINEER

. CROSS-SLIDE ANGLEPLATE MOUNTING

SINGa lathe which has no face should be the same top and difficult to control, is best accom- vertical slide or slotted bottom. The clearance at the sides plished on a bed of sand on a metal U cross-slide, one is handi- can be checked by swivelling the plate over the source of heat, quench- capped in performing many milling plate; but if there is vertical error, ing at near dark straw. operations which complement nor- it must be corrected by packing with For mounting an angle plate, a shimstock at Y or Z. pair of slots permit variation in radius mal turning and which are speedily In preparing the angle plate for to align to the bolts in the tee-slot performed and precise in the mounting, a recess is usually needed of the slide. However, slight opening results when there are means for to accept the spigot which normally with a round file keeps bolt centres making set-ups. locates the top slide. The correct size parallel with the face. In other cases, Of course, bars, plates, clamps and drill can be used after a preliminary holes can be drilled. simple fixtures,contrived for the run with a smaller one, each being Parallel and angular settings to the occasion and mounted on the top run in the chuck with the angle plate lathe axis can be made with a test slide, are in some ways substitutes. pushed up by the tailstock. bar and protractor, C, a projecting But they fall considerably short of For a flat-bottomed recess, the lips screw or pin in the bar providing the facilities offered by the broad of the larger drill can be modified clearance at the tailstock for a parallel face of a vertical slide, or the sub- by grinding after they have entered setting.For an angular setting, a stantial area of a slotted cross-slide. some distance. But the problem in protractor is used to the bar-or up many cases is lack of a suitable drill to a driving plate or faceplate when -and then a piloted spot-facing that is more convenient. By GEOMETER cutter in silver steel or cast steel rod An example of work done at a It is difficult, too, to mount a large is required, B. parallel setting (although it can be casting on the top slide, or even a This tool-left a few thou larger at performed in other ways) is machining machine vice, which, once set up, its cutting lips than the measured the radius on a saddle casting with can often be used for small parts. diameter of the spigot-involves plain a fly-cutter, D. For this, the casting Fortunately, the disadvantages are turning followed by sawing and filing is held between small angles by a greatly alleviated by using an angle for flats and clearance angles. Harden- bolt through its bore, and is prevented plate in place of the top slide, locating ing is done normally; but tempering, from turning by a bar studded to its it according to one’s needs, face to with stubbiness making heat-flow face and the angle plate. El face with the chuck, at right-angles to it, or at intermediate angles for special operations. Components can then be clamped in orthodox ways, and the machine vice mounted in a variety of positions. Cutters are no problem, neither are they expensive. Single-point tools serve for facing operations when mounted in blocks with an off-set in the independent chuck. Radii can be machined with pre-determined off-sets of such tools, or by fly- cutters set in mandrels and run from the chuck with support from the tailstock centre. Silver steel or cast steel rod is usually to hand for making spot-facing cutters, end mills, and keyway cutters. In relation to the spindle axis, all basic mountings of the angle plate are made in its setting on the cross-slide, except the important one of squareness in the vertical plane. This might be presumed, though it would not necessarily obtain-in precise terms- even with a true angle plate. So a test, A, is advisable. Lacking an indicator, a piece of rod can be bent, gripped and swung in the chuck, when clearance to the 12 JANUARY 1961 41 MODEL ENGINEER MILLING

on ANGLE PLATES by slide feed, across to the straightedge; and for a boring operation, the slide is clamped. ITH an angle plate mounted horizontal platform or faces to which The cast bed of a horizontal steam on the cross-slide (as de- components can be attached. engine is a fairly common example scribed in my last article), For many operations, especially on of outsize work. From inability to the effective capacity of the lathe large components, it is necessary to machine it, the underside may have set up to horizontal and vertical centre to be filed true, the casting being is extended over a wide range of lines-which are first marked on screwed to a block of hardwood in milling and boring operations. components in normal ways. For the the vice. Flatness can be tested on The outcome is that one can under- horizontal centre line to the lathe the surface plate. take machining of certain items axis, the surface gauge can be used For milling the crosshead face, a of equipment, or parts of models, from the lathe bed, aligning its point set-up can be made on the angle which were previously beyond one’s to the centre line at each end of the plate,. A. Ordinary clamps may be scope from sheer inability to component. The height of the point used mstead of lugs, or bolts may be swing them or otherwise set them is set from a horizontal line on a piece of material in the independent By GEOMETER UP. chuck. This line is itself set to centre Many operations on smaller com- height by adjusting the chuck jaws ponents are also facilitated when the and testing at 180 degrees. Then the passed through the bed. Alter- slide-mounted angle plate is the only scriber transfers the setting to the natively, a strap bolt may be used on alternative to the top slide for setting component. the cylinder mounting face; it con- up--the lathe having neither a vertical For the vertical centre line, a flat sists of a stud brazed or welded to slide nor a cross-slide with slotted face is needed at the lathe axis ex- flat material. face. Small components which can tending from the chuck. It may be After milling the crosshead face, be set up by straightforward clamping the face of a half-round bar, or a turn the angle plate 90 deg. to deal can, like large ones, be mounted piece of rectangular bar off-set in the with the cylinder mounting face. direct to the face of the angle plate. independent chuck. With the face at For this, to get to the lathe axis, For others with right-angle faces, it the axis, a small straight-edge can be the engine bed is mounted with the is advantageous if the angle plate is held or clamped to it, and set vertically crosshead face to the angle plate, supplemented by a smaller one? or by by turning the chuck. Then the vertical with packing if necessary, B. right-angle blocks, providing either a line on the component can be adjusted, Machining outside the flange, and boring for the spigot on the cylinder cover,should precede the facing operation, while the centre line remains to give the setting for clamping the slide. These operations are performed with an outside tool and a boring tool, Cl and 2. Ordinary facing and outside flange- machining operations, of which these are examples, can be performed with tools in blocks, adjusting the chuck jaws for swing and radius. Boring operations require short stiff tools, similarly set to radius by the chuck jaws. For narrow slots, such as ports and keyways, endmills are advisable; though on occasion some extra width is possible by wobbling slightly in the chuck. For operations like these,. the second angle plate mentioned (mounted on the main one) facilitates setting up, though by the use of clamping plates and blocks, set-ups can be made without it, D. The engine cylinder, for example, can be bolted between two plates W-X which are fitted by studs to blocks Y-Z, also tapped for studs to hold them to the angle plate. The crankshaft can be set up in split blocks, one of which is drilled and tapped for studs. q 19 JANUARY 1961 73 MODEL ENGINEER CENTRE FINDING on the lathe

N marking-off procedure, centres tapped up or down half the difference, are commonly located from and the line is brought to it by adjust- I crossed lines. Then the inter- ing the work.. After a few tests and sections are carefully centre- adjustments, the line is on the lathe axis. punched for the drilling or boring For work in the independent chuck, which follows. With relatively- A, one line S-T is trued first, and then large holes-whether to be finished attention is given to the other U-V, by drilling or boring-it is often followed by a further check on the advisable to locate dividers in the first line. For work on the faceplate, centre-punch indentations and to where a straight edge is parallel to scribe circles corresponding to the a line, the line should be trued first. holes, as guides. Then a backing strip can be bolted to Alternatively, the faceplate, to keep the work in with a height gauge, hole positions alignment while the other line is may be “ boxed in ” with squares. trued. Otherwise the first setting can One relies, in drilling, on the drill’s be lost in unclamping to adjust the following accurately into the original second line. indentations, using small drills first, To locate a centre in the middle of opening out gradually, and checking parallel material, a line can be scribed from each edge, B.Here the required position is W, while X is the distance By GEOMETER from the end.Two lines Y and Z are each scribed the same distance from their adjacent edge, and each brought to the same horizontal setting with from the scribed circles or boxed-in the material in the chuck. This can positions. Before the final drilling, avoid a scribing error in centralising. of course, small errors from concentricity can often be corrected by Using a centre punch judicious use of a round file. To find the centre of work mounted In lathe work, a similar principle on the angle plate is another job done can be followed, in so far as a job with a scribed line. Any convenient can be eased over in the independent metal block can be marked for height chuck, or adjusted on the faceplate with the line, and then clamped to the or angle plate, if it is seen that a bore angle plate, C. Adjusting this on the is not machining accurately into faceplate, the line is brought true in position.But it is generally preferable two positions. A further way of for the set-up to be initially precise, making the setting is to use a mandrel as a generated bore cannot wander between centres with a suitable off centre-unlike one produced by gauge, D. drilling; and, given the accurate set- Finding a centre from a tiny centre up, one can concentrate attention on punch indentation can only be done the size and finish of the bore. with a needle, E. It is fixed in a little Finding a centre from a pair of ball located in a countersunk hole in crossed lines needs only a scribing springy material, so as to be able to block, and a flat plate on which to wobble. A sleeve of cycle-valve use it if the lathe bed is one with rubber will hold the needle, and the inverted vee guides. It is not necessary springy material can be bolted to a to centre punch the position of the holder for the tool slide. The slide bore, scribe a circle, or box it in. is eased up, the point put in the The lines alone serve for location. indentation, and the work trued to Each in turn is centred by testing steady the needle. horizontally with the scriber point, A piece of thin plate, F, with its turning the lathe, and adjusting the top edge at centre height, provides a work and scriber as required. quick centre finder for scribed lines, After a line has been brought and is a means for setting the scriber horizontal, the lathe is turned through point, for an upward tilt of which a 180 degrees. Then the line is above clip with an overlapping edge is used or below the point, and so this is on the plate. q 26 JANUARY 1961 103 MODEL ENGINEER BUILDING UP COMPONENTS SINGGstock sections, off-cuts, the piston valve cylinder is mounted and pieces of material which in them by clamps. With this con- U may be too small for other struction, the blocks can be prepared. purposes, it is often possible to They can be bored and radiused, the ports can be cut in them by drilling build up parts cheaply-or to and filing or milling, and matching machine them from the solid- ports can likewise be made at the and so save time and effort, or ends of the cylinder. avoid some tricky operation. Tech- Forsilver-soldering or brazing, the nically, too, there may be advan- blockscan be clamped on a rod and tages m fabrication-though, con- stoodon the cylinder. Afterwards, versely, the parts might have been they can be cleaned by reaming or equally as efficient as castings. lapping where they grip the valve cylinder: and the corresponding areas Still, if there is nothing in it either on this ‘cylinder can be turned true way, then cost, effort or skill may after steam and exhaust bosses have be the deciding factor. been attached. Fabrication is thus Building up parts may also stimu- strong and precise, and the work late the imagination to break down on the ports straightforward. complicated components into ele- mentary solids like cylinders and Covers for cylinders Cylinder covers are components that can be built up, the spigot of the By GEOMETER top one being attached by a nut, B. Sometimes the bottom cover mounts cubes, and one may go on to recog- the cylinder on pillars, which means nise such features as bosses, flanges, that it must be cut from plate mate- ribs and lugs, as smaller versions rial, with the piece incorporating the applied to the main structure. Possi- spigot and gland boss sweated to it. bilities can then be discovered in To get alirmment. the cover is drilled oddments of material, and a use can or gored, and the gland boss and be found for them if one has nothing spigot are turned, but left on the rod. definite in mind but is merely seeking After tinning, the pieces are sweated. “ something to make.” Many at- Then the rod is rechucked to finish tractive models have begun in this the cover and spigot and drill and way. tap for the gland. In particular, stationary steam en- Time in turning pillars with flanges gines,in small and medium sizes, can be saved by pressing on a shaped offer many possibilities for using collar each end, Cl. Tubular pillars stock material. There are various can be built up by brazing in a ways of building up that most im- stepped plug, 2, turning to size, portant component, the cylinder. The facing to length and threading. actual cylinder, the part in which the Pedestal bearings can be machined piston moves, as distinct from the from rectangular stock in the in- whole component with the valve dependent chuck. A saw cut, T-U, face, can be machined from a piece removes the cap, and after refacing a of solid or cored round stock, facing, second cut, V-W, removes the pedestal. boring, and turning on the outside Both are faced on the underside in to leave flanges. For the valve face, the chuck. a rectangular block can be radiused Other components that can be to fit the outside of the cylinder. built up to advantage are small cast using a fly-cutter, or “boring ” on iron pistons and port bands for two- an angle plate; and after drilling or stroke engines, D. The piston is milling the ports, the block and the bored from rod, and the bosses- cylinder can be tinned on their joined by a neck-are drilled each abutting faces and sweated together. end and brazed in. Continuing the Adaptmg this principle, a piston drilling breaks out the neck. The valve cylinder can be built up, A. port band is from tubing, with Instead of the one block as for the bosses XY and transfer way Z brazed slide-valve cylinder, there are two at the set-up shown. The bosses are blocks, R and S, silver-soldered or overlength for screws and are faced brazed to the steam cylinder, while down afterwards. El 2 FEBRUARY 1961 133 MODiZL ENGINEER FITTINGS FOR

By GEOMETER sometimes overcome the difficulty by SMALL LATHES mounting the work on a piece of parallel plate and clamping this to the AKING a lathe more con- On a small lathe, where the bed is faceplate. But the convenience is not venient to use, or more near to the chip tray, easy operation comparable to that offered by an M precise in operation, is a of the handle for the clasp nut to the auxiliary faceplate, C, mounted on process that most owners pursue, leading screw is sometimes obstructed. the regular one. With access to the This can be a drawback in screw- back, nuts can be fitted to the bolts of more or less, persistently through cutting, and can cause delay whenever small clamps, while a screwed fitting the years, according to their in- the saddle is to be positively located can be directly held by a nut. clinations or the work which they for facing operations. However, an A disc or square of plate about have in hand. extension, B, on the drum for the 1/4 in. thick can be secured by studs No lathe maker, of course, can clasp nut permits operation outside or countersunk screws (to keep the foresee every individual circumstance the chip tray. working face clear of bolt heads), of use. A cheap lathe cannot include To reduce work on the fitting, the the studs or screws passing through all the refinements, and consequently cap and the spindle are machined parallel distance pieces. Set up, the there is usually scope for modifications separately, the spindle having a stem plate can be faced true, and reference and additions, as solutions to specific to rivet or screw to the cap. Then marks made for future fitting. A problems, or simply in anticipation they are brazed together inside the circular plate can be trued con- of future needs. cap, cleaned up, and polished. The centrically from the outside, while a On a small lathe, it is often possible original handle is removed, and the removable plug will serve the same to speed tailstock clamping by modi- ball end of the spindle drilled for the purpose in a square one. fying the arrangement and substituting substitute to come conveniently into Loosening tight chucks is a problem a handle for a nut-which can be a one’s hand-fingers over the spindle. that can be solved in various ways. considerable convenience in routine For very small work, an auxiliary Back gear may be engaged and the operations like centring and drilling, faceplate has advantages over the one drive pulled in reverse to bump a jaw when the tailstock may have to be supplied with a lathe because small to a block on the bed. Alternatively, brought up and moved away im- work needs to be placed where the the backplate can be drilled radially mediately afterwards. end of the spindle comes in the normal for a tommy bar, or in the face for Where the clamping is by a plate faceplate. It is true that one can a large pin spanner, D. I3 and nut on the far side of the tailstock, a handle can be fitted, A, to work like the one on a production lathe. A new plate may be needed to carry the gib piece or guide which bears on the bed, and two reaction screws X-Y can be fitted in place of one. They are tapped into the plate and fitted with locknuts, and their ends bear in dimples drilled in the tailstock body. Through them, minor adjustments are made to keep the handle in a good clamping position, and the rear one, X, acts as a stop for the handle when it is loosened PLUG back. The handle itself can be plain rod, or turned taper from the solid with a ball end, and then brazed or welded to a boss which is tapped for the main stud. Here a Whitworth thread gives extra axial movement for clamping and freeing, compared with a finer BSF thread-although the BSF may be used for the end of the stud in the tailstock. Initial major setting of SPINDLE the handle is done by facing the boss, I II-- and the final setting through the reaction screws. 9 FEBRUARY 1961 165 MODEL ENGINEER PUNCHES and CHISELS

LTHOUGH standard punches for finishing the bores of D-washers, By GEOMETER meet the requirements of a (3) for making small hexagon box great assortment of ordinary spanners. In turning, the blanks of A cutting punches are advisedly given work, there are inevitably times slight clearance (a few thou only) back filed with the slight clearance given to when they cannot be used by from the working ends; this can be cutting punches, and hardened and reason of size, shape or design. done, too, when filing hexagon tempered in the same way. Sometimes, of course, a simple, punches. Foil and spring blades can Whenever possible, hollow punches quick improvisation will solve a be punched directly on a flat lead for cutting soft materials should punching problem; at other times, support, while the bore of a D-washer be tapered to the piece to be wasted, the requirements may demand can be finished from a drilled hole, or the taper on the punch is likely special punches, particularly when as can a box spanner. to deform the piece to be used. This In small sizes, forming punches are is revealed at Dl where a hole punch there are cutting, forming or sizing chiefly used for turning rivet shanks has an outside taper, by comparison operations to perform. The special into neat snap heads, C. Silver steel with D2 when the taper is inside. punches can be in silver steel or can be used, or mild steel finally case A similar effect of a chamfer at a cast steel, hardened and tempered. hardened. A punch blank is centred cutting edge is sometimes apparent The ordinary pin-punch is a straight- and drilled a short distance, and then, in using an ordinary chisel E, where forward tool, with a length-diameter with the end heated bright red, it is there is sliding along line W-X that ratio to meet normal needs, which driven on a suitable steel ball- an attempt can be made to counteract means that it may dither or even bend afterwards thrown away, Facing and by tilting the chisel. A flat-sided at the extraction resistance offered heat treatment follow. For the heads chisel cuts relatively easily along line by a beefily hammered-in taper pin. of rivets, a hold-up is made similarly. Y-Z. On large punches and chisels, All is obviously well-once the pin A sizing punch, D, is useful for protection against chipping is pro- has been started, and the ordinary straightening the ragged edges of a vided at the heads, F, by applying punch can be used for driving it out. row of holes into an accurate port. bronze, or sometimes by using rubber For the start, an improvised punch In silver steel, it can be turned and sleeves. may be of silver steel rod, hardened and tempered, and conveniently held in a toolmaker’s clamp, A. Alter- natively, the shank of a broken drill or tap may be used; and if the end is slightly too large, it can be reduced by grinding a short distance. If you are making a pin-punch, it is rather wasteful to turn it from silver steel rod when a short length of actual punch size can be inserted in A D a well-fitting hole in a mild steel 0 holder. Should this not be possible, 0 a somewhat larger piece, depending on the drill or silver steel, can always be substituted, its end turned to the required size. The principle is applicable also to centre punches of various dimensions. When, by mischance, a punch insert snaps off with the holder, chuck the holder and turn back its end until you can get a grip on the re- maining piece in the vice and pull it out. A punch insert is hardened by heating it cherry red and plunging in water. For tempering, it is polished bright with emery cloth and then laid on sand on a piece of sheet metal, or on sand in a large spoon, and heated slowly from below. Watch the piece carefully; mid-brown is the colour at which it is quenched again in water. This method of hardening and tempering applies to special punches, B, as may be used (1) for driving holes in metal foil and spring blades, (2) 16 FEBRUARY 1961 191 MODEL ENGINEER TYPES OF

BORING BAR

SING different types of boring of adjusting the whole bar to vary A bar, either running with the cutting radius. Alternatively, a ,o U the lathe spindle or oper- rotating bar can be supported by the tailstock centre, or by a plain or ball ated from the tailstock, many bearing at the tailstock. Sometimes operations can be performed that the fixed steady can be used with a would be difficult or impossible long boring bar, or a bearing can be without them. Both the rotating provided on the angle plate on which and non-rotating types of bar work is set up. may be provided with single-point For accurate turning, requiring the tools or fly-cutters, set to radius, travelling or fixed steady, it can be an or with double-ended tools giving advantage to start with the jaws diameters over the two cutting bedding fully. Machining them to radius is a job for an overhung boring edges. Both types of bar may be bar, A. A travelling steady moves t used with or without pilot guides, with the saddle; while a fixed steady depending on the work. is clamped lightly to the bed in front Most boring bars can be machined of the saddle, and so moved along. from good quality mild steel-with Many operations are possible with care to obtain a smooth finish to an overhung boring bar when work functional surfaces. For one-off or is set up on a slide-mounted angle occasional use, they need not be case- plate. But the deeper a bore must be hardened, as this implies grinding to taken, the likelier it is to cause chatter size afterwards; and sometimes bar with an unguided bar. For open bores, or rod material which has an accurate when the bar can go right through, ground finish can be used as it is. the answer to this problem is found in boring and bushing the angle plate, and using a guided bar. The boring, BAR TOOL By GEOMETER B, is done by opening out with an I \ overhung bar from a drilled hole, which is then fitted with a bush, For use in the tailstock, boring bars secured by a thin nut, to. take the have taper shanks to suit the barrel, guided type of rotating bar, C. and when bumped in firmly they hold The outsize job which cannot be well. An unguided bar should carry swung on the faceplate or moved by a double-ended tool to give a balanced the saddle sets a boring problem that cut which counteracts wobble. A may sometimes be solved by a grubscrew will secure the tool, and rotating boring bar fed from the with careful feed it will clean out tailstock. Support and drive for the cored holes in castings that are set bar can be arranged, D and E, using up on the faceplate or angle plate. a bored bearing block on an angle A guided bar may be similarly used plate on the faceplate, and fitting the through open castings, its forward bar with a pin which comes down end extended to fit in a bronze or flat to a block fixed by a countersunk duralumin bush in the lathe spindle. screw to the faceplate. Several holes Its rigidity is naturally far superior in the bar extend its movement, when HOUSING and so it can be employed for more the pin is changed from one to the PAD accurate work. Using a single-point other-given that the bar will enter tool, a succession of cuts can be the bore in the lathe spindle. taken, setting it out for each one; Support and feed at the tailstock and when the tool wears, it can be can be provided by a plain bearing resharpened, unlike a double-ended with a single ball thrust at the end tool which must be renewed. of the bar. But an arrangement A rotating boring bar may be a using a ball bearing, F, is to be stubby, overhung type used directly preferred-the pad centre being fitted from the chuck or faceplate., or from in the lathe spindle to finish the a special fixture, all of which admit housing for the bearing. El 23 FEBRUARY 1961 221 MODEL ENGINPFR

. COUNTERSINKING and DEPTH DRILLING

0R functional purposes, countersinking of small numbers F of holes can be done by judgment, checking frequently with a pattern screw or rivet. It is, however? a process on which uniformity is by no means easily obtained, and once an error has been made-a countersink produced too deep-there is nothing one can do about it. Unfortunately, too, such an error is rather obvious to a scrutinising eye. When a countersink is too deep, there is an increase in diameter round the head of the screw or rivet-which a non-technical person can see after

By GEOMETER it has been pointed out. On the other hand, a countersink which is too shallow leaves the head of the screw or rivet upstanding, to catch anything such as a cloth rubbed over the surface. Of course, one may “ correct ” this effect by filing the screw or rivet flush. But by so doing, the head is made visibly small; and if there are several screws in an assembly, and they are ever removed,. they must all go back to their original holes. For easy assembling, then, as well with included angles of 90 deg., which ground, can be made from three as for good appearance, the heads means that one must use a rose bit pieces of flat strip metal, B. Two are of countersunk screws or rivets -particularly for wood or soft bolted together at the ends with should be just flush with the surface in material-or grind a twist drill to spacers,and the third is hinged which they fit, Al : and for important angle, or make a tool in silver steel. between them. The drill lies in the two work, sorting is advisable to eliminate This is essential for screws with a as in V-blocks. Setting of the gauge any that are non-standard. It can small parallel diameter at the top to is done with a protractor, or from be done with a piece of plate that which the countersinking tool should pencil or ink lines on paper, both for has been carefully countersunk as a just give diametral clearance. The normal drilling angles of 118 deg. and gauge. ordinary centre drill has an angle of countersinking angles of 90 deg. For cheesehead screws sunk in the 60 deg. A twist drill has an angle of In countersinking by hand drill, a surface, A2, the fitting is again fairly 118 which agrees fairly well with flat scriber, B, on a small block, helps critical. Usually the heads should rivets of 120, as does the centre drill to control depth; it is held by one not stand proud; but if the holes are exactly with those of 60, and so at hand while the drill is used with the noticeably sunken, the edges can times these drills can be used. other. Either the shank of the drill, collect a chamfer of dirt-which For a flat-bottomed hole, A2, a or a sleeve on it, has a line for refer- normal wiping will not remove. Still, twist drill can be modified, A4, to ence? which is easily seen against a a little sinking in this instance is follow in the hole enlarged by a coating of marking blue. generally acceptable. Greater toler- twist drill of normal angle. A shallow On a drilling machine, depth ance is possible for flat-bottomed flat-bottomed hole, A3 needs a pin- control of countersinks or flat- counterbores to take hexagon nuts drill or flat-ended cutter in silver bottomed holes is maintained by a or screws with hexagon heads, A3. steel with integral pilot; while a suitable stop, C, or a gauge with a Even here, it is desirable to have near- countersinking tool, A5, which must sensitive pointer, D. Sometimes, the flush fitting of nuts or screws and uni- have a pilot, is best made with it pointer can be applied to the sliding formity in depths of holes. separate to facilitate filing the teeth. sleeve or quill of the machine. When Usually, countersunk wood and A simple gauge to check the angle this is not possible, a collar grub- metal screws, and rivets, have heads of lips on a twist drill, as they are screwed to the drill is used. q 2 MARCH 1961 259 MODEL ENClNEER GAUGING SMALL and By GEOMETER MEDIUM while four pieces of accurate rod and a pair of plates, B, provide a larger dimension, X. These methods can be useful when you have no micrometer BORES to ensure a high standard of accuracy. For preliminary undersize testing, the callipers can be adjusted loosely in F you have a standard outside the plates; and should oversize be micrometer and inside callipers, necessary,shimstock can be used I a great variety of small and with the rod or balls. medium sized bores and short For precise spacing of plates, drill length dimensions-both outside shanks may not be sufficiently accur- and insids - can be verified to a ate-which goes for many square high standard of accuracy. For lathe tools even though they may be merely checking a bore, its size ground all over. Preferably both is carefully taken by the inside should be checked before use. For gauging directly without use callipers, and these are used in of callipers., silver steel rod makes a the micrometer to obtain the good substitute for an ordinary plug actual dimension. C gauge. Tapered at the end, it indicates In machining a bore, close checks 0 the approach of finished size. Long can begin when it is still several thou tapers can be turned on pieces by undersize. The micrometer is set, angling the top slide, but slight say, 0.010 in. under the dimension, chamfers require only careful work and the callipers are adjusted to it. with a smooth file and emery cloth. Then fairly heavy cuts can be taken Care is required in checking bores until they will just enter the bore. with a taper gauge when it is not to For important work, this may be be entered fully. If a bore is parallel the time to resharpen the tool and throughout its length, a taper gauge, take two or three fine cuts-to C, can be let in to a reference mark Y, eliminate slight bell mouthing from which may be the size from which a trial cuts, see the sort of finish pro- reamer is used; should the bore be duced, and ensure that all is satis- bell-mouthed (from trial cuts, or the factory. tool cutting keenly at the start), If there is doubt about the lathe mark Y may still be flush, but with cutting parallel, this procedure should the bore at a smaller diameter, Z. be adopted well before the finished This could leave too much for the dimension, while ample metal still FiELER GAUGE reamer. A right-through taper gauge, remains for you not to risk running or a check with callipers, reveals the near the finished size in making ~PLUNGER error. testing cuts after adjustments. For special cylinder bores, an There are, of course, many varia- accurate check in machining and tions from this basic method, some lapping is kept with a plunger plug employing callipers.If the bore is to gauge, D. It may have a screw at be finished by a reamer, you can take the end with an eccentric diameter the size from it, boring out a suitable for adjustment; or there can be a washer in the chuck until the reamer slot into which feeler gauges or strips will enter to finished size-the washer WASHER of shimstock can be slipped beneath , then serving as a reference for the the plunger. For larger bores, a calipers. As most reamers have a telescopic gauge, E, can be used, its taper at the end, a second and tmder- plunger extended by a spring and size washer provides for a pre-check, locked by a rod and screw in the with the callipers used well into the body. Either can be set or checked bore to verify parallelism. by micrometer. Dimensions may be taken with the For checking a recess, a quickly- callipers in two pieces of flat plate made gauge, F, consists of a washer which are lightly bolted to rollers or soldered to the shouldered head of a to short pieces of silver steel rod, bolt, and then turned to size. The A. This material is usually very other gauge for smaller and deeper dia- accurate. Three steel balls may be meters is machined from rectangular similarly employed with stiff flat mild steel and provided with an washers to obtain their dimension, X; adjusting screw. q 9 MARCH 1961 291 MODEL ENGINEER

. ACCURACY in awkward drilling

HEREis always some risk in are separated by substantial webs of drilling relatively small holes, metal. If all are not in line, the width T and when the process follows of the slots or ports is increased. important machining operations Careful centre-punching helps to avoid the faults. It is obtained, A, by using precautions for its success are several centre punches of suitable- obviously worth while. A small diameter silver steel, pushed through drill is so easily broken that, in a tight-fitting rubber bands and gripped twinkling, one may be faced with in a toolmaker’s clamp. the awkward problem of removing Running holes together to form a the broken end, or even with the slot or port can be done with pre- alternative of scrapping the whole paration and a suitable set-up, B. part. Normally, a drill would run off- Drilled holes usually have to be course, or jam and break; but by accurately positioned and spaced. pluggmg the first and each subsequent hole (except the final one) with rod of PLATE This can be done by careful marking- the same material as the job, the drill off and centre-punching. Then, with is given support. The rod should fit the line of the holes at right-angles to well-not tightly or loosely-and be the surface, drilling can proceed. filed to a step at the surface. It can It not infrequently happens,that be bent over, packed, and clamped. holes are at an angle to a surface, Careful centre-punching will position following holes, or a jig plate will guide the drill. Final truing and sizing By GEOMETER can be done with a punch. A similar principle of support admits of producing half-holes at the edges of faces? an example being and added to the normal hazard of the fitting of a ring locating peg in the drilling is the chance of misalignment. groove of a small piston, C. The Again, half-holes may be needed for groove is filled with a push-fit piece fitting pegs, holes crossing others at of material, and the hole is drilled tangents for fitting cotters, or lines of and tapped at the joint line. Then, holes to finish as slots All are with the material removed, the peg reasonably straightforward, given pre- is screwed in and filed down just paration. beneath the surface of the piston. To reduce the chances of faults in Drilling holes at angles is best important drilling, it is advisable performed with a guide or jig for before starting to examine a drill accuracy. The need is particularly for sharpness and lengths and angles apparent if there is risk of spoiling of cutting lips. If it is not satis- important work. Typical examples factory, it should be reground. When are drilling a steam passage from the this is done by free-hand grinding, the end of a cylinder to a port, D, and drill can be tested afterwards on a drilling the lubrication hole in a piece of material similar to that of crankshaft from the crankpin to the the job. It should be chucked firmly main journal, E. For a guide, a metal and run without wobble. Freeness plug is machined to clamp to the of cutting is important, as is easy cylinder, and its head is cut off to clearance of the drill in the hole if it angle. For a jig, two blocks are has to go to considerable depth. bolted together and bored for the Frequent clearing of swarf is necessary crankpin, and the guide hole is and lubrication is helpful, according drilled at their abutting faces. BUSH \ PLATE to the material. Central drilling of pins at a given When rows of holes are placed distance from the heads-an awkward straight and close together to form job-can be performed in a machine slots or ports, small errors in spacing vice, F, using a shouldered bush have exaggeratedly adverse effects which IS slightly smaller than a pin on results. Some holes may. break and is fitted in a plate over the jaws into neighbouring ones, while others of the vice. q 16 MARCH 1961 323 MODEL ENGINEER SUPPORTS for CHUCKS and FACEPLATES By GEOMETER

VEN in the best organised driving plate of the lathe, A. The the screwed material in the boss can workshop, improvisation has disadvantage is that the extra height likewise be drilled and tapped for a E a part to play, and when may obstruct use on some drilling countersunk screw. equipment is lacking there is no machines. If the driving plate has two Screwcutting material for mounting choice but to use what is to hand. opposite holes, a piece of steel bar a chuck is straightforward work on It may lead to the discovery, too, can be bolted to its face, by which the lathe; and if duralumin, hard the plate and chuck can be held firmly aluminium alloy or brass is used no that for some types of work, the in the bench vice. The three-jaw difficulty should be experienced in substitute equipment has advan- chuck can, of course, be similarly obtaining a good thread. The tailstock tages over that which would have mounted when round parts require centre can be used for support, and been used. handwork. the blank undercut at the chuck end, On this principle, a four-jawed Another support for either chuck for the thread to run clear, D. The independent chuck can be compared can be arranged, B and C, using a driving plate can be used as a gauge. with a machine vice. The vice is used piece of flat plate with four round Then the piece can be parted off, on the drilling machine, in the bench pillars of a length for the boss of after drilling and tapping for the vice, and on the lathe for gripping the chuck just to clear the surface. countersunk screw. At the opposite components and pieces of material. This reduces height compared with end, in the reduced diameter, a cross These are its standard functions. Yet support on a driving plate. The flat slot permits use of a screwdriver for most of the different shapes and sizes plate may be steel, though if alumin- speedy fitting and removal. can be held just as well in the in- ium is to hand its use will save weight. For use as a bench surface plate, a dependent chuck; and many of The four pillars can be faced carefully lathe faceplate can be supported on irregular form can be set up much to length and drilled and tapped three bolts in tapped holes in its rear easier and held far more securely in centrally for each to be mounted by face, E, while for mounting firmly in the chuck, which has four individually a countersunk screw. To secure the a vice, F, two strips of steel should adjustable jaws at right-angles, against chuck in its support, as when the be bolted to this face to be gripped the two gripping surfaces of the vice. plate is to be held in a bench vice, endwise with the boss clear. q Essentially, then, given that the diameter and depth of the chuck are acceptable, it is lack of a support or mounting which prevents its wider use. The same may be said of a large driving plate or the faceplate of a lathe, either of which can be used as a substitute for the bench surface plate, for marking off and testing. Here the A faceplate has a distinct advantage in 0 SURFACE that its slots admit of bolting a component if necessary, or of mounting an angle plate securely to provide \ a vertical face to which material can DRIVING PLATE be clamped. Should it be necessary to jack a component level, a bolt may be fitted in a slot in the faceplate with a nut either side to regulate height. Again, a straight-edged strip can easily be bolted to the plate to serve as a guide for a surface gauge when checking demands this control. For use on the drilling machine as a machine vice, the four-jaw chuck can be set upwards in a shallow hard- ’ PLATE wood box. Support should be at the rear face of the chuck, or at a substantial diameter on the backplate, and so tipping cannot occur with the pressure of drilling, as it would were the chuck supported on its boss. For support there to be effective, the chuck must be mounted on a piece of screwed material in a base which can be arranged using the ‘23 MARCH 1961 355 MODEL ENGlN EER CARE AND USE OF CHUCKS By GEOMETER

N essentials, lathe chucks are removed; the chuck is-taken off, and the shoulder on the lathe spindle no more than specialised vices, cleaning is done from the back with with a well-regulated bump, to fit I much more complicated in paraffin, a brush or syringe. In a firmly but not with excessive trghtness. construction of course than or- bad case, the backplate should be Removal should not then be a dinary bench types, and capable of removed, B, to clean the vital threads problem. On a back-geared lathe, gripping a greater variety of shapes. Y. Graphite grease or special assemb- this can be effected by using backgear ling paste can be used on threads and with a broad-based block on the bed Still, as gripping is their function, jaws of chucks to promote smooth up to a jaw of the chuck. For an their efficiency depends upon the working and guard against wear. independent chuck which is narrow, accuracy of their jaws, which is There is often no choice but to with its jaws above the gap, a long particularly important as they must grip components or material near the bar, D, can be used to the bed for be relied on for squareness and ends of the chuck jaws, which in removal. running truth. time results in strain and wear. It Using’ a cup-type grinding wheel, With an independent chuck, for is to be avoided when possible, worn chuck jaws can be trued on example, the squareness of end-facing especially as a much firmer and more the lathe with a set-up of each on the on flat-sided bar material depends on accurate hold always follows from vertical slide. Those of a self-centring the accuracy of the jaws; and in placing material well into a chuck. chuck have to be ground for centring using a self-centring chuck, we rely Sometimes narrow material can be work, and so a check should be made, on the quality for squareness, and also held as effectively by reversing the E, for wobble with material gripped. on the accuracy of centring to bring jaws of an independent chuck, C right, The jaw with the lowest reading is about true spinning or concentricity. as by using them normally, C left. ground first, F, to dimension Z; then Often a bench vice will withstand At the same time they are aligned. the others are longer than Z according a good deal of hard use, such as Gripping large diameters like this to their wobble. To set each jaw on fitting a pipe on its handle for extra gives the additional advantage that the slide, a pair of parallel steel blocks leverage, gripping at the side of its the jaws remain guided, often full can be fitted to it on the chuck, and jaws instead of centrally, hammering length, in the body of the chuck. then transferred with it to the slide, to bend or straighten material; while In fitting a chuck, it should go to where they are clamped. El neglect to clean the handle and slide results in sticking and wearing. Obviously, these are in the category of “ Don’ts ”if efficiency is to be maintained. Broadly, but more emphatically, and for like reason, the same or similar actions are to be avoided with lathe chucks. Clogging of jaws, screws or scrolls of chucks with swarf or fragmented metal is not usually a problem, except in boring operations. In ordinary use, a centre can remain in the spindle taper, or a cork be used instead, while a well-fitting rubber disc, A, next to the chuck backplate, prevents particles of metal from entering any exposed threads. Usually, of course, it is advisable to stand a chuck with its jaws down, to keep INDICATOR metal out of the threads; and always before a chuck is fitted, the threads in the backplate and on the spindle nose, and the faces of both, should be examined and, if necessary, cleaned. After right-through boring operations, when metal particles have been whirled in a chuck, their presence often prevents its jaws from being opened freely. Rather than strain and indent the threads by forcibly opening the jaws, they should be closed in when the work has been

30 MARCH 1961 385 MODEL ENGINEER Accuracy in

at the ends. It applies also to four- CHUCKING jaw chucks, whose jaws like those of the self-centring type can be trued by grinding. In the lack of other means, a tool post grinder can be used ENRRALLY,at a first chucking turners: “ Always tighten on number with a grinding wheel that will easily of bar stock in a self- one.” Then there is no doubt about enter the body of the chuck. To hold G centring chuck one expects which jaw (or screw) should be used. the jaws of the four-jaw type, a ring slight eccentricity on checking with By combining this principle with is mounted at the second step, and a surface gauge, or testing with a that of the sleeve to protect work, the inside faces set spinning con- the highest standard of accuracy is centrically for grinding, B. scraping cut. This is because the obtained at first chuckings. A piece A ring outside the jaws will not, chuck grips over a range of sizes, of material, such as brass, is chucked, of course, serve for a self-centring and it is very difficult to eliminate faced, centred, and then drilled and chuck, because of the reverse thrust from a screw the periodic errors reamed, or bored. After dotting to on the scroll. Each jaw must be which cause small variations in its No 1 jaw, it is removed and hack- separately clamped. It is done with pitch. The scroll of the chuck, sawed along the side to make the a bolt in the tee-slot, a plate and which moves the jaws, is of course split bush, A, in which bar stock or a packing piece, C and Dl. Alter- a type of screw. turned components can be accurately natively, a hook clamp can be made and safely gripped. for each jaw, D2 and 3. With either On measuring machines and jig- When such a bush is tapped in the jaw holder, closing pressure should borers where feedscrews must be to bore, it can be used for chucking be applied to the chuck before final the highest standard of accuracy, screwed components, though an unclamping. there are special arrangements to split, tapped mandrel serves just as For grinding jaws separately, using well. In fact, mandrels of various a cup wheel, a set-up can be made By GEOMETER types machined in the chuck and on an angleplate on the faceplate, used immediately (or dotted for re- locating each jaw by its groove on a setting) frequently provide the best squared strip on a parallel plate, E, compensate errors of pitch; or the solution to the problem of ensuring and then clamping; while to reduce errors are tabulated so that allowance accuracy in chucking-or in rechuck- width on chamfers, each jaw can be can be made for them. Inevitably, ing for second operations. mounted in a pair of angle iron then, in commercial chucks, there are Even with split bushes or mandrels, supports, F, and clamped through likely to be small built-in errors, which accurate chucking may not be possible hook bolts for grinding on face for accurate work one should be when chuck jaws are bell-mouthed Y-Z. q prepared to avoid. Accuracy at a first chucking- particularly when a self-centring chuck has been strained-can often be improved by packing at a jaw, or two jaws, with shimstock or foil of suitable thickness. Tinplate may also D be used, and even paper when the 0 jaws have considerable gripping surface and the diameter of the work is fairly large-otherwise concentration of pressure will cut through the paper. Similarly, in chucking hard, heavy BUSH pressure will mark the surface of the -RING work, unless protective foil, preferably brass, is used as a sleeve round the work or as strips at the chuck jaws. At a second chucking of bar stock, accuracy can be promoted by ob- serving two points. One-the more ‘GRINDI NG important-is to dot the stock to WHEEL No 1 jaw before unchucking, so that it can be replaced as originally fitted. The other is that in the original and every subsequent chucking one should tighten on No 1 jaw (or screw). Thus, one duplicates the original conditions, neither replacing nor tightening the work at hazard, however long the time between chucks. From this comes the axiom of many 6 APRIL 1961 MODEL ENGINEER SETTING and SUPPORTING

LATHE TOOLS By GEOMETER

ANY factors influence suc- oil give a mixture with plenty of cess in a turning or boring finish-improving, lubricating body- M operation;and a know- but it is advisable to clean down the ledge Of the characteristics of the lathe after use. For roughing and finishing cuts, lathe, its response to adjustments, height setting of a turning tool is its reactions to certain handling, an important factor. For heavy must always constitute a large part roughing cuts, endwise to the material, of a turner’s skill. the tool edge can be fractionally It is knowledge that comes gradually above centre A-S, so that slight spring of course, in the beginning often will tip the tool approximately to growing out of mistakes and mishaps. centre height. This is all right, but too Deplorable as these may seem at the high a setting, too much spring, time, they often teach a delayed deepens the cut; and by increasing lesson when they indicate what unfavourable factors, the diameter of should not be done on future occa- the work can be unexpectedly reduced sions ; or they may be positively -riskily so, if roughing is near to beneficial in stimulating an analysis finished size. of factors by which those that are Other hazards occur with a low unfavourable can be eliminated. tool-setting, B-T, which may be Among unfavourable factors are exaggerated through the inherent inappropriate shape and setting of down-spring. There is a reduction in tools, and their inadequate support effective rake on the cutting edge, when they must take the thrust of and the pushing of the tool below broad or heavy cutting, or when a centre tends to lift the work. It is feature of the work calls for their particularly marked with a parting-off considerable overhang, as in deep tool which is not cutting freely. parting-off operations, or in machining Resistance of the chip U, combined the crankpin on a balanced crank- with spring in the work, can move the shaft. centre of this Y from that of the For heavy cutting, as in roughing spindle W, upwards and towards the out, a square or straight advancing tool, with components X and Y. edge on the tool gives the shortest Jamming and tool breakage can length and the freest cutting. Tough speedily follow. material like steel can be stripped For most turning operations, then, smoothly off in a cool flat ribbon, a tool is advisedly set at centre height, whereas, using a round-nosed tool or slightly above. For roughing cuts, for a correspondingly heavy cut, the its shape can be as C, left, and for metal is compressed as it is torn off, finishing cuts as C, right, with a small and is then broken into short rough honed flat Z. lengths, or at times into hot blue Height setting can be expedited fragments. This is hard on the job, with a surface gauge D, its pointer the tool, and the lathe. adjusted to a rod or block which has On the other hand, for finishing been machined to centre height. with light shallow cuts, a round- This initial adjustment can be per- nosed tool, or one slightly flattened formed optionally on lathe bed or behind its rounded nose, gives an surface plate. improved finish, as the length of its For setting boring tools, a drilled cutting edge equals or exceeds the sheet iron plate, E, can be used. As advance per revolution. You thus it can be moved along their shanks, avoid a markedly spiral finish-a it indicates clearance, and packing shallow thread on the work. required, which is particularly useful For either operation, a combined for tools with forged shanks. lubricant and coolant is usually Support for a turning tool can recommended ; and various cutting often be arranged through packing, oils and suds are to be obtained. A F, left; while a narrow tool can be good home brew is made by flaking supported by a steel strut studded to soap thinly from a bar, dissolving in a block on the cross-slide, its top face boiling water and then mixing with veed to engage a ground vee on the car engine oil. Sufficient soap and tool. El 13 APRIL 1961 447 MODEL ENGINEER LARGE HOME-MADE MICROMETER

AKING equipment to mea- ment is possible over an extended can be produced slightly oversize- sure to a high standard range. In addition, the head bar regulating the opening of the die- M of precision is not so carrying the micrometer spindle can and finished by lapping with fine difficult as it might be thought be used in other precision equipment abrasive compound using a split by anyone who has never attempted by making provision to bolt or clamp brass or aluminium lap. it on. Lapping can also be the means of it-a fortunate circumstance for Both pieces of bar, which with the finishing the gauges by which the those who need accuracy on spacer form the frame, are drilled micrometer is set. These can be of dimensions beyond the 1 in. of and tapped 40 t.p.i., when clamped mild steel rod, carefully faced a few the popular standard micrometer to the faceplate, the one for anvil X, thou overlength. Then a guide block and cannot afford additional equip- the other for spindle Y. Each is can be faced, drilled, reamed, or ment. slotted from the end and is fitted bored in the chuck, so that a gauge Most micrometers, of course, have with a screw for closing the slot, the can be pushed through it, C, for a threads of 40 t.p.i., which are the anvil being gripped firmly (after brass or aluminium lap to be used at same as those employed for many setting) and the spindle adjusted to a the end. Two accurate gauges in a model fittings, and are specified when smooth working fit. Locking the sleeve give 2 in.;if the micrometer nuts are to be run on thin-walled spindle to hold a setting is done from has 1 in. movement, it can be opened tubes, or when they are to be screwed a threaded plate in the slot of the head to 3 in. Three gauges give an initial into the tube plates of boilers. Com- bar-the plate being forced down by 3 in. and the micrometer an ultimate mercial taps and dies for cutting another when the knurled nut Z is 4 in., and so on. tightened. The head bar carries a For dividing, the disc (which is scale, with 1/40 in. divisions, against gripped by a knurled nut to the By GEOMETER which registers the disc on the spindle spindle) can be mounted with a with its 25 divisions. change wheel on a mandrel. If you Mild steel can be used for both lack other means of indexing, the these threads produce excellent results anvil and spindle, though the-working arrangement D can be rigged, using when they are used with ordinary end of each can be casehardened. angle iron to the lathe bed and two care and skill, and so it is quite For a high-quality fit, spindle threads bars held together by a rubber band. q practical to use them for micrometers. The principle by which measuring to 0.001 in. is obtained on the ordinary micrometer can likewise be followed in the home-made equipment, by providing a similar thimble or sleeve, or even a disc, divided into 25. Then 40 (t.p.i.) x 25 equals 1,000 (1 in.), with one division giving 0.001 in. Dividing can be done from any change wheel with a suitable number of teeth. Having settled the principles and decided means for producing the ---- - more important parts, you can con- _ _--- lip\ sider the general design. Here sim- SCALE plicity, solidity, and built-up con- BAND struction have much to recommend k\ them, with all parts made separately. . SPACER This tends to confine the scope of errors; and you can use the “ measuring head ” for a purpose other than the one originally intended. A large home-made micrometer, as at A and B, provides an example. The frame or body can he built up from two pieces of rectangular mild steel bar, with a steel distance piece or spacer bolted between them. The length of the spacer controls the gap of the micrometer, and so by having a number of such spacers, each longer than its predecessor by the movement LOCKING PLATE of the micrometer spindle, measure- 20 APRIL 1961 419 MODEL ENGINEER LAPPING bores and shafts

expensive tools; whereas lapping, at to run it in the chuck and hold the very small cost, can make a better lap. With the lap chucked, abrasive ADJUSTING job than the best of reamers. is kept away from the chuck, and it is A great many materials can be used possible to plug the chuck with rag for laps, and all the softer metals for additional security. If possible, and alloys found in a workshop. this should be done when, for any Depending on the type of lap, lead, reason, the set-up must be reversed copper, brass, aluminium alloy, cast and a cylinder lapped in the chuck. iron and mild steel are all smtable. For most purposes, we need look no further than the last four. by GEOMETER Similarly, there is a large variety of special lapping compounds, but two are sufficient for general use; the While the cylinder is still gripped, fine grade compound used by garages the chuck can be removed and plugged for grinding in (lapping) valves, and from the back. The bed of the lathe the sludge to be found in the bottom should always be well covered with F all mechanical production of Brasso tins. The one can be used several sheets of newspaper. processes, lapping is per- for stock removal, the other for The lap should be turned almost finishing. to size, and then smoothed by filing 0 haps the most fundamental For lapping a bore on the lathe, it and therefore the most important. and tapered at the end for the cylinder is usually better to run the lap in the to push on. With abrasive smeared on Nowadays, of course, with modern chuck, A, and hold the cylinder than the lap, it may be too large, so that equipment,much can be done further filing is necessary to get the without it, so that it may be only initial fit. Back gear may be used for occasionally that we are thrown a start, followed by normal drive back on lapping, for some special Paraffin and I as the bore enlarges. or unusual job. thin oil help to speed and regulate How were the first surface plates cutting; and final smoothing can be produced ? They were made, if not D done with thin oil. by scraping, then by lapping-match- 0 Since a lap wears in use, adjustment ing three surfaces (in pairs) through a is usually necessary. On a cylinder fine abrasive. And how will lenses lap, B, it can be done by slitting with be produced in the future ? The a hacksaw and fitting two screws, one method will be by lapping-because Y to expand the lap, the other Z to of the geometrical precision required. keep it parallel. A short lap for a Geometrical precision is what lap- blind bore, C, can be adjusted by a ping essentially provides, though it single screw. Such a lap, used in a has great merits, too, in its slowness drilling machine, is extremely useful and its capacity to deal with the for sizing the inner end of a bore which hardest materials. Because of the cannot be reached by a reamer owing slowness, it is difficult suddenly to to the taper. make a bad mistake in lapping, as Other laps can be made and can easily be made in turning. Frac- adjusted as at D. A short bush (1) tions of a thou can be removed can be slit and used on a rod; a small without difficulty-in making gauges, lap can be drilled, slit, and then for example; and components and expanded by a taper pin (2), or slit tools that have been hardened and and expanded by a flat wedge (3). cannot be touched by other means A shaft lap can be made by drilling (except grinding) can still be lapped. and reaming a single piece of flat For model engineers, the process is stock, E, and drilling and slitting for particularly advantageous for finishing a bolt. For a crankpin, a lap can be the bores of cylinders when they have made by bolting up two pieces of been bored as accurately as possible flat stock and drilling and reaming, F. on the lathe. It is true that they could A very simple type consists of a be reamed. But large reamers are half bush on a bar. El

27 APRIL 1961 MODEL ENGINEER ACCURATE

A thin gauge_, c, can be made from sheet metal. It is sheared oversize and Centring and drilling finished to micrometer by draw-filing -rubbing edgewise on a Swiss file. If the gauge is made undersize in the process, the metal can be stretched for By surface, and the centre punch lightly another attempt by careful tapping GEOMETER tapped. Then the block is ready for with a hammer on a block. the lathe. With any of these centre-locating A development of the device consists devices, the basic setting from the in slotting the plate for securing and edge of the work can be obtained as at adjusting the stop strip with a counter- D, using a block gauge (instead of IVENthat a centre punch dot sunk screw, B. This gives the same calipers) between a plug in the centre can be located at the exact accurate setting for locating centre punch hole and the stop strip. When G point where it is intended punch dots from the edge of work; the stop strip is of known thickness, and a cut-away, w, which can easily distance Y can be taken over the strip to be, there is every chance--even be milled or filed, admits light from a and the plug by micrometer. in ordinary drilling-that the re- torch to facilitate the sighting of Centring in this way obviously sulting hole will be accurately spacing lines for two or more holes. demands centrality of the centre punch positioned. A small well-sharpened An alternative method of spacing point, which is ensured as at E. drill can be used to provide a holes is as at c. The position of one Standard silver steel rod is used for pilot hole from the centre punch hole is centre punched. Then the hole its good fit in reamed holes. After dot; and if the required hole is is drilled and reamed and a plug is being faced and pointed in the chuck, large, the opening-out can be done inserted. From this plug, a distance the punch is hardened and tempered. x to the edge of the plate can be Then its point is finished against a in stages with several drills. This obtained with calipers; or if there is a grinding wheel on a mandrel in the reduces to a minimum the chances cut-away on the plate a thin gauge can chuck. It is in a hole in a bar on the of the hole’s running. be inserted to a second plug in the slide and is turned by a knob. If the job is done on the lathe, its centre punch hole. The plate is then The general principle of centring and precision depends upon the accurate preferably of a size that admits of drilling is applicable, F, to cutting a setting of the centre punch dot-which holding to the work with a toolmaker’s large hole, z, by drilling a series of small is obtained by using a needle [ME, clamp. In this way, with a thick plate, ones, while maintaining control over January 26, page 103], or a pointed drilling can be done direct. their spacing by a pin in the jig plate.@ rod and indicator [March 30, page 405]. The work can be clamped to the faceplate, or mounted on an angle plate on the faceplate., either method being suitable for obtaming the precise rise-to-centre of the angle plate. The setting of an angle plate is, of course, particularly important, as any error is inevitably transferred to the rise-to-centre of components machined on it. Accuracy is ensured by using a centre-punched block, A, which is clamped to the front edge of the angle plate, and the centre punch dot is brought true by adjusting the angle plate on the faceplate. For locating the centre punch dot precisely from the edge of the block, a plate is used which has a reamed or lapped hole for a short centre punch, and a stop strip is held by a toolmaker’s clamp, to give the centre distance. One way of obtaining this distance is to push the centre punch through the plate so that callipers (set from a micrometer) can be used between the punch and the stop strip-with allowance for the radius of the punch. Once this setting is obtained, the device can be laid on the block on a flat

4 MAY 1961 545 MODEL ENGINEER HOLDING and INDEXING

CHUCKS By GEOMETER

HEN a lathe is the only is possible for the final adjustment of major machine tool in a work in the chuck. W workshop, there are often On a gap-bed lathe, a way of times when it must function in securing the chuck is as at B. Two ways other than those originally pieces of rectangular steel are each bent to extend from the jaw to the intended. This is particularly so bed. Then they are drilled for a in model engineering with the clamping bolt, which can be fitted workshop built around the lathe. with distance pieces if clearance is Certain types of milling, planing, restricted. The material can be bent grinding, lapping, indexing, and in an old vice,, or on a small anvil so forth, have all to be done on if the section is heavy and must be the lathe in the absence of special- heated to red. With a heavy section, ised machines or equipment. each piece can be drilled and tapped at the lower end for a screw to the bed to Many non-standard operations, permit angular adjustment. based on milling or boring machine Both ways of holding a chuck practice, are performed with a cutter apply whether it is a three-jaw or or tool rotating in a chuck or holder, four-jaw, and so admit of three or working on a component mounted on four basic settings-with, of course, a slide or saddle. All told, they. form a check on work from a square or an extensive and varied group, which surface gauge on the bed. For holding greatly extends the scope of the lathe. a four-jaw chuck on a flat-bed lathe, A further spread of operations an alternative way is as at C, with a follows when components (on which pair of jacks on a flat plate. Four turning operations have perhaps basic settings can be made, with already been performed) are held delicate final adjustment; but care is stationary in the chuck or on the needed to avoid slightly jacking the faceplate or angleplate for machining chuck if this would be detrimental to or grinding with slide-mounted heads accuracy. or attachments. When a chuck cannot be held by its jaws,or a faceplate must be Locking devices secured, a clamp, D, can sometimes D For this group of operations, the be used on the boss of the backplate 0 chuck or faceplate must be held firmly or faceplate. Two aluminium blocks often in some particular angular can be easily faced, drilled and bored, relationship with features already and two flat bars bolted up with an finished; accurate resetting or index- adjusting screw in each. ing is frequently required. Examples Either a three-jaw or four-jaw are found in machining keyways, chuck can be held behind its key teeth of gears, the tangential flanks of sockets by a band which can be cams, and other angular flats. Even anchored to the bed of the lathe, E. for certain filing operations cm the A bar, clamped to the bed, mounts a lathe, it can be an advantage to have long stud through a block attached the chuck firmly held against rotation. to the band by countersunk screws On a flat-bed lathe, a simple way -or by silver-soldering or brazing. of securing the chuck is as at A. A Thus fine settings can be made. piece of suitable angle-iron or rect- For indexing from an initial setting, angular-section steel, bent at right- an index plate, F, can be made from angles, is drilled through one flat sheet steel or iron to rivet to a band for bolting to the bed, and through clamped to the flange of the chuck the other for attaching a clamping backplate. Then the stud of the hold- plate by a bolt. Packing pieces can ing device can be provided with a be interposed to the jaw of the chuck; pointer. Dividing of the index plate and if they are rounded at the jaw can be done in any of severa1 ways; ends, and the angle piece has a slotted for turning it and cutting out its hole for sliding across the bed, a centre, it can be clamped to a ply- small amount of rotational movement wood backing on the faceplate. q II MAY 1961 577 MODEL ENGINEER Miscellaneous

TESTS andSETTINGS By GEOMETER

SEof a lathe on varied work tains an angle of a few degrees (from plungers is adjusted by its screws to calls for many tests and parallel or square), a check of the give uniform readings on the in- U settings, including checks angle can be made by moving the dicator. When the lathe is rotated, of the machine itself as well as of top slide 1 in. by the micrometer the plungers describe a true cylinder, tools and components. The total collar. The difference in reading on and the slide can be quickly set the indicator is then the “ taper per parallel by the indicator. With of such verifications and adjust- inch ”of the angle, which can be spacing Y 1 in. or 2 in., taper per inch ments-major and minor-is cer- taken from tables. is obtained for tapers. tainly very large, perhaps infinite, When an angle plate contains an Difficulty in setting a top slide for no other machine so well error and is to be used on a surface from outside to inside tapers can meets the requirements of profes- plate, it can be packed as on a faceplate, often be overcome by using a mandrel sional and amateur workers. In though for this purpose adjustable with plungers, D. The slide is moved fact, almost everyone employs a feet are advisable, B. Just behind to set them to turning tool or indicator; the vertical face, there can be clamped then, with the lathe turned 180 deg., dodge, knows of one, or-come a flat bar with a screw each end. A to that-can evolve one to aid the angle for setting the boring tool clamp with a third screw gives three- is obtained. an operation or overcome a diffi- point support. Should testing of For a“ taper per inch ” setting, a culty. components require the angle plate mandrel can be made as at E, with As a lathe comprises major align- to be tilted through a few degrees, Z 1 in. or 2 in. The screws are set to ment in its construction, it is suitable it is easily done with the screws. micrometer over the mandrel-and for checking squareness of faces on A parallel setting for a top slide care should be exercised in chucking components or tools. By mounting can be obtained with a mandrel, C. this. these on the faceplate, and employing Because of possible error on the An adjustable centre, F, provides an indicator, a high standard of chuck jaws, maximum wobble on the for testing or producing tapers, and precision is possible. An example is mandrel should be in the plane of is made with a hard centre in a flat testing the accuracy of a square, the two shouldered, equal-length plun- bar which is bolted to another attached as at A. gers. This is arranged after an in- to a shank to fit in the tailstock First, the top slide can be set dicator check. Then each of the barrel. parallel to the lathe axis, using a mandrel in the chuck, or turning a piece of rod for checking. It is assumed that the faceplate is flat- not concave or convex: otherwise, a piece of true bar would need to be clamped to it and packed out with paper or shimstock at one end for setting up the square. D if there is slight wobble on the 0 faceplate, the point of maximum run-out should be at right-angles to - the blade of the square-which will ensure that the square is trulv mounted to the faceplate. By running the indicator along the blade, any error will then be revealed. If one is present, adjust the top slide to give a uniform reading on the indicator, turn the lathe, and reset the indicator. The reading will then show the error as doubled. Almost any component with two faces at right-angles can be checked for truth in this way. In particular, it is advisable to verify an angle plate which is to be used on the faceplate for mounting work, as any error of alignment will be reproduced in it. Paper or shimstock may be used to bring the face of the angle plate true to the faceplate. When a component or gauge con-

18 MAY 1961 609 MODEL ENGINEER By GEOMETER

CENTRING and DRILLING methods

N general work there are wise on the face of each,, where the pin provides a secure hold and lets the many ways of inducing the is to be, a line is scribed and then drill through. I standard of accuracy required deepened to a shallow V with a three- To guide a drill for a pilot hole, in operations of centring, drilling cornered file. With the pieces clamped, which is often all that is required and boring which settle the posi- the Vs come together to guide the for accuracy, a clamp can be as at D, drill to make the hole for the pin, made from mild steel bar and a pair tions and spacing of holes. For which is gripped when the faces of of setscrews. The pieces can be draw- a simple job a centre punch and the pieces are again draw-filed. filed true, and their width checked drill can suffice. For a special Similar Vs guide the drill for the with a micrometer. A clearance hole component or part of a jig, tool- drill hole. This is drilled with the jig W can be drilled, and a collar C made maker’s buttons may have to be in the chuck, at which setting a round for gripping in the clamp to drill the used-unless one has access to nose can be turned to facilitate re- hole for the drill through the clearance equipment like a jig borer. chucking. The jig can be used in hole. Scribed lines on the work Between these two extremes, all the chuck or vice-bench or machine locate the clamp. sorts of dodges are possible to help type-with washers or a collar setting Collars of definite size locate holes in promoting the precision-dimen- the pin. from the edges of work, or along a sional, geometrical or both-which is When it is important for square or clamped straightedge. For example, a so simple to specify but often not at rectangular material to be drilled collar 1 in. dia. locates centres 1/2 in all easily achieved. centrally, the job can be done as at C from an edge. Such a collar can be To drill centrally through a round by machining a collar from round bar. used as a gauge when bar is being rod, a bush can be machined in the Without unchucking the bar, it is faced to length, as at E, with the final lathe to the diameter of the rod and centred and drilled, and the outside cut on the line X-Xl. centred and drilled at the same diameter of the collar is turned to the Parallelism over the edges of work setting. For use, it is clamped on top width of the bar to be centred. Two is ensured by facing on the angle of the rod in the machine vice, the clamps hold the collar in place on the plate, F, setting either to the faceplate jaws of which align them both. work-though one with a forked end or to packing or gauges, as Y-Z. q Larger work which is relatively short, like a disc or collar, can be set up on an angle plate on the faceplate, A. The angle plate is mounted the required distance from centre, and the job clamped centrally to it. The central setting is obtained by using a surface gauge or indicator with attachment to equalise the diameter about the lathe axis. Alternatively, the setting can be done to scribed lines. With the angle plate located vertically from the lathe bed wtih a square, and using a surface gauge or pointed tool at centre height, a centre line is marked on the angle plate. The job is marked with a longitudinal line each side, in V-blocks, and these lines are set to the centre line on the angle plate. This can be done on a rough-turned trunk piston when the longitudinal lines have been located to the gudgeon pin bosses. Careful centring is followed by drilling, in stages if necessary; and this in turn is followed by boring with a tool or by reaming. For centrally drilling small pins, a jig is advisable; and the type at B is easily made, even in very small sizes. Two pieces of rectangular mild steel bar are draw-filed, clamped, drilled, and dowelled with rod. Cross- --- _._ -._. 25 MAY 1961 641 MODEL ENGINEER Setting-up

HOLLOW COMPONENTS By GEOMETER

HE great variety of hollow to No 1 jaw ensures accurate resetting made by first shouldering a piece of parts which are encountered in the same chuck, and a short plain mild steel; then, gripped firmly in the T in general work calls for diameter near the thread admits of chuck, it is centred, drilled, tapered, almost equally varied means-in truing to indicator in an independent turned to size and undercut, and slit detail at least-m order to set chuck. All sorts of turning, facing and lengthwise by hacksaw. A cone on a threading operations can be done on drawbolt through the spindle expands them up. Ordinary chucks serve components on such a mandrel, it. On such a mandrel, a long tube for the simpler and more straight- without doubt about their accuracy. can be faced, its free end supported forward jobs when components Parts that are too narrow to align by the fixed steady. can be gripped by their jaws on by pushing on a plain mandrel can Components that can be set up an internal or external surface. sometimes be gripped between a by the steps of chuck jaws-but There are definite limits to this shoulder and a washer by a nut at the at the risk of wobble or jumping out means of setting-up. With facing end of a mandrel. With small piston can be given support in various operations alone, it may be necessary rings this is essential, for the practice ways. One way, D, is to use a centred to true anything from a tiny nut to a in home production is to slit each ring plate kept up by the tailstock centre. piece of solid-drawn tube for a boiler and compress it, as shown, on a For a mounting by the chuck itself, E, barrel. At times the length as well mandrel, B, for turning the outside when a normal drawbolt cannot be as the ease of deformation of tubular diameter. Then it has inherent used, a plate Y can be screwed to the parts can create problems in setting springiness at its finished size; and chuck backplate, or one Z can be up; and there are many occasions if required, it can be machined with placed to pull against the chuck jaws whenparts have to be set up for its inside and outside diameters when a bolt is put through the com- second operations in ways which eccentric to help in equalising thrust ponent. ensure concentricity between their all round against the cylinder wall. For setting up a large tube, a turned inside and outside diameters. By comparison with plain mandrels, block can be used in the chuck and a For parts with finished bores, the expanding types have the advantage centred plug at the tailstock. Alter- best means of setting up is a mandrel of accommodating dimensional differ- natively, the block can be turned after -to be certain of concentricity of ences in the bores of components. screwing to a board and bolting this diameters and squareness of ends. It A simple expanding mandrel, C, is to the faceplate, F. can be turned in mild steel-though brass or duralumin may often be equally suitable-to run in the chuck, with or without support from the tailstock centre, or to mount between centres and drive by a carrier. Mach- ined slightly oversize with a smooth surface, it can be finished with a small taper from the entering end, using a ---COMPONENT Swiss file and emery cloth. Generally, it is advisable to smear the surface of a plain mandrel with , thin oil before the part is twisted on firmly by hand. Then, if slipping occurs, the bore is not scored. Oil helps, too, when the part is being E removed. 0 In machining, a series of light regulated cuts is recommended, particularly for facing the end of a part, Y--l Lz COMPONENT like the cylinder, A, where the dia- \ meter may be large and the cut at WASHER imes intermittent. For tapped or internally screwcut components, a threaded mandrel, B, can be made at a single setting in the F chuck, undercutting it at the shoulder 0 to clear the thread, and producing this by die from the tailstock or by TUBE screwcutting. A centre punch dot 1 JUNE 1961 673 MODEL ENGINEER SPANNERS and devices for TIGHTENING By GEOMETER and LOOSENING

N general assembling and dis- to the thread. Occasionally an octagon mantling work, even an ex- nut will be used, to limit the size I tensive standard tool kit some- over comers. times fails to deal with a special The spanner is as at A. To make it, a piece of steel is machined the nut, bolt or screw which has been width of a flat on the nut; it can also used to meet some demand of be the length across two flats. if the design. Often, too, standard nuts, nut is not very large. Then using it bolts and screws are awkwardly as a former, the spanner material situated, and when they must be can be bent in two pieces for a hexagon loosened and tightened for servicing 1, or an octagon 2. The former work special spanners or adapta- serves again for welding the pieces tions of standard types are clearly -holding in the vice or a clamp. Then the box spanner is welded to a worthwhile. backing piece 3. Any welder can do Of course, in restricted locations, the job with the pieces prepared. standard spanners with jaws at an Extra reach is given to a tubular angle can be used in various ways, box spanner, B, by a solid or tubular turning flat types over to change the extension fixed with a rivet or bolt. angle of attack and so rotate a nut The extension can take a tommy bar, or bolt a fraction of a turn. Flat or a nut can be welded to it to take ring spanners,in themselves and a ring spanner. Another idea for a when turned over , admit of still finer tubular box spanner is to slot one angular application, and do not hole, so that the tommy bar can be require so much clearance for their moved from a right-angle-which, at use as open types. times, is necessary to clear obstruc- Limitations of some locations can tions. Slotting is done by drilling be overcome by using curved or an extra hole,_ or holes,. and run- cranked spanners, open or ring types; nig mto the ortginal one with a round while other normally inaccessible file. places can be reached by tubular The problem of loosening a slender box spanners or socket spanners, cap can usually be solved with a sometimes used with a ratchet wrench. piece of strong cord and a bar, C. Nevertheless, it is surprising how The cord is wound two or three times often such variety proves inadequate. round the cap, tied, and twisted up When a welding torch is at hand, by the bar, which is used as a lever. a modern chrome spanner can be Such a cap distorts if it is gripped in quickly bent or cranked to deal with a vice, or the corresponding part may a special situation-or a cranked be easily broken, so that an all-round spanner can be slightly straightened grip is essential. or reset. Heat from the torch should A flange may be stopped from be concentrated in the area where rotating,while its securing nut is bending or straightening is to be done. tightened or loosened, by a piece of One end of the spanner is in the vice. flat bar held by a bolt to abut to The other end is pulled to angle. another bolt, D. Alternatively, with If you have an old vice, this work, like a cut-away on the bar, two bolts TWIS any other involving heat, should be can be used through it. done in it. For turning large screws, or screws For a large ring nut, which may be in awkward places, a driver can be made awkward to turn, a spanner can be from flat mild steel, E, its two ends made from rectangular mild steel bar. bent initially at right angles and then CAP The dimensions of such a nut defeat one twisted at 45 deg. to improve I proper use of an adjustable spanner angular working. For a screw or with limited depth of jaws, though cap requiring a pin-spanner, rod can their opening may be ample. The be bent U-shape and used in a tool- nut may be in a recess and thus maker’s clamp, or bar can be drilled SPANNER inaccessible, or so thin that it squeezes and pins driven in, F. I 8 JUNE 1961 705 MODEL ENGINEER HOLD-UP S and SPACERS for By GEOMETER RIVETING

SSUMING that design is correct, efficiency and neatness are A almost inseparable qualities in riveting, which is an essential operation in many fields of profes- siona l an d model engineering. Correct design means, of course, that with due allowance for scale and contingent problems the boiler or other component has a sufficient numbe r of rivets, of suitable size and material, disposed to take B stresses in shear and give an 0 acceptable factor of safety. At practical fulfilment, the result of much thought and many decisions XD-UP on these matters is satisfying to an en ginerr and can be pleasing to a layman, for neat lines and groups of snap head rivets have more to offer visually than the finest welded joints. As always, of course, between .CER design and product lies the track of -UP practical production well-beaten, perhaps, but with pitfalls which require preparation to avoid. Plates to be joined should be drilled so that rivets fit closely, and the burrs and punch can be used as aA with t depressions, the material should be are removed at the edges of holes by the hold-up gripped in the vice. chamfered by filing to clear other filing or lightly countersinking. Rivets Ordinary care gives a good result; rivet heads. must be of correct length, their heads and for a simple job, the endplate can For riveting down the length of an properly supported on hold-ups, and be invisibly soft-soldered by fluxing open-ended barrel, a hold-up D,, their shanks turned with snap head in the barrel, putting in a lump of consists of a piece of heavy mild steel punches. Long rivets can be shortened solder and heating, so that with tilting bar with a movable collar. One end by snipping the shanks and filing and turning the solder runs all round of the bar is gripped in the vice each one to length with the rivet the joint. Tinning before riveting is and the other held by an assistant. pushed through a hole in a piece of helpful in this wor. k Expanding spacers for working at flat steel bar, which can be faced to When a hold-up cannot be used a distance down barrels can be made thickness if necessary. direct, it is advantageous if,_in design, on hydraulic or mechanical principles, Hold-ups and punches can be in rivets have been arranged in opposi- as a t E an d F. The body of the mild steel or cast steel, made by tion. Then they can be fitted and hydraulic spacer is from rectangular dimpling the material with a drill, finished in pairs, using a spacer as at B. mild steel bar, drilled and reamed heating it to red, and driving it on to Here the spacer is a screw and blind a slant to take a well-fitting plunger a hard steel ball. The facing of each nut, each machined from hexagon rod with the open end of the hold plugged. should be so that the shoulder of a to tighten with spanners with the Another hole is drilled from the end, snap head is just proud of the end. rivets in place. breaking into the first, and is tapped The tools can be used soft, or mild For supporting at a distance down for a pressure screw which is fitted steel can be case-hardened, and cast a tube (like a flue), a spacer can be after filling the holes with thick steel hardened and tempered. Hard made from round mild steel, as at C. grease. copper rivets can be annealed by The piece should be drilled and tapered The mechanical spacer consists of heating them to red and plunging inside on the lathe for a cone and bars W and X hinged at Y, at a small them in water, to aid in forming snap drawbolt. With rivet head depressions off-set from the rivet line. One carries heads on then shanks. made, the material can be cross- a screwed-on jaZ. w Tightening the For riveting the flanged endplate drilled and slit to expand. Round bolt expands the spacer between two into the barrel of a boiler, a hold-up the diameter, between the rivet head rivets. q 15 JUNE 1961 737 MODEL ENGINEER Setting and machining

ANGLE PLATES By GEOMETER

OLTED to the faceplate of a backplate .Packing blocks set the lathe, an angle plate provides plate from the headstock, and shimstock corrects twists and brings the B a platform on which flat- top face true. After facing. the plate based components can be clamped. is set up again for the other face. In practice, convenience in setting For machining an inside face, the up (or even the ability to set up angle plate can be set up on the certain parts) depends on the size vertical slide, to use a fly-cutter or and type of the angle plate; while large end-mill from the chuck. In the alignment of faces and bores, this set-up, the problem of overhang which are subsequently machined, from the chuck and chatter of the cutter can be overcome by running depends in turn on the accuracy the cutter spindle in a steady, as at of-the angle plate. dhen set up, D and E. its face should be at right-angles The spindle can be in mild steel, to the face of the faceplate. and the’bearing in brass, bronze or When components are relatively duralumin, clamped on tubular pillars small for the lathe. there is no problem mounted on a plate bolted to the in actually mounting the angle plate. lathe bed. Shimstock washers correct It is bolted with its flange towards small errors of height .The angle the edge of the faceplate. But when plate is mounted by drilling and components are relatively large, tnere countersinking a bar to take lock- is the problem of setting the platform nutted countersunk screws and push- far enoug h from the snindle axis. PACKING ing in a T-slot of the vertical slide F. The corners of the flange may overlap By turning the lock-nuts, the plate can the edge of the faceplate and prevent then be tightened to the slide. q rotation ;or at smaller off-sets, it may be impossible to fit two bolts for a secure hold-one, of course, being inadequate. This problem is encountered on straight-bed toolroom lathes, and on modellers lathes, even gap-bed ones, which are often employed for relatively possible slight warping. By showing outsize work. With all, the solution up the pattern to the faceplate and is the same-an angle plate bolted, vertical slide. the most suitable over- as a t A, with the flange towards the all dimensions can be obtained. centre of the faceplate.Two bolts Machining of the casting is really are easily fitted, there is the maximum a job for a planer or shaping machine, length of platform X,, which can be but it can be done on the lathe, with a convenience for clamping com- care. In fact, if the plate is machined ponents, and a smaller balance on a planer or shaping machine, and weight (not shown) can be used. is not quite accurate, it can be cor- When the accessories do not include rected on the lathe. This applies to an angle plate of this type, its making most angle plates. A test of accuracy, can be thoroughly worthwhile--even as at B, is made with a surface gauge. if it is not required immediately, for Alternatively, a pointer can be used the outsize job will come along sooner on the slide. If you have an indicator PLATE or later. In addition, such an angle you should, of course, use it instead. plate offers similar advantages for Any error is corrected by packing setting up work on the vertical slide with shimstock or foil at Y or Z; but for milling operations. to save this on every occasion the For a casting in cast-iron, the plate can be set up, as at C, and faced pattern can be two pieces of flat true. hardwood screwed together, the screw The same set-up is used for an holes plugged with putty or plastic unmachined but reasonably accurate LOCK wood .The thickness of the wood casting. First, it is smoothed by filing. NUTS should allow for a machining cut of Then holes are drilled and tapped for VERTICAL about 3/64 in. on each face, and attaching it to a driving plate or chuck 22 JUNE 1961 769 MODEL ENGINEER PEENING and other SECURING STOP 1 methods SLEEVE

N the normal or annealed state, most metals and alloys I stretch and flow under impact or heavy pressure, which makes possible a huge range of manu- facturing processes, from beating small articles in sheet metal to cold forging heavy components- besides subsidiary operations from simple riveting to expanding the skirts of worn pistons by shot- blasting the interior. On the principle of displacing metal, parts can be secured against movement and light assembly performed. Thus, a nut can be prevented TUBE COLLARS from unscrewing by judicious use of a centre punch at one or two positions on the end thread of a bolt-which will not prevent the nut from being re- By GEOMETER moved later; while to secure a hard steel ball in the end of a screw to take thrust (or spring-load in a housing rd DRAW BOLT as a lock), the end of the hole can be lightly peened to contain the ball. Another application of peening is as an additional security for a shrunk- On occasion, a ball valve will be should be carefully scraped clean and in seating for a poppet valve as at A. fitted, as at Bl, with a stop or sleeve coated with jointing compound. When shrinking-in alone is relied limiting its lift. When the sleeve is In certain assemblies, a lead shot upon, the seating can be straight- not screwed in, it can be secured by may be fitted in a hole after a screw sided and fitted in flush with the peening. A tool for the work is a which is not normally to be removed, surrounding metal. But when the hollow punch, B2, with a short or which provides a pre-set adjust- seating is to be additionally secured guide-the guide being turned from ment. Such a shot, Dl, is fitted by by peening, its extreme outer corner the solid, or provided by drilling up punching like a Welch plug. A plain should be slightly chamfered, then the punch and fitting a piece of rod. plug may be secured by staking the the surrounding metal can be care- Cast steel heat-treated, or mild steel end of its hole, D2, with a small fully hammered or displaced over the case-hardened, can be used for the rectangular-ended punch; while a chamfer. tool, and for others used for peening flush-fitting screw, D3, can be held Instead of performing the peening thrust balls, or spring-loaded balls, by centre-punching metal into its slot. by hammering, a tool for the work into the ends of screws or housings. For expanding ends of tubes, a can be made by machining a holder Metal flow in another way is taper punch, El, can be used, followed in mild steel with three hard steel employed to secure core plugs or by a mandrel, E2, with a let-in ball balls let into the face at a radius Welch plugs in the jackets of many or hard rivet. The tool can be turned slightly greater than that of the water-cooled engines. As at C, a with a tap wrench or brace. The seating. There should be a spigot to plug is a mild steel concave-convex projection of a rivet, E3, can be locate in the seating, a central stud disc, which is placed in a machined varied by fitting directly in the with locknuts and a cross handle for recess and tapped centrally with a mandrel or to a filed flat. turning. Grease holds the balls in punch to expand it. When it rusts Other expansion tools may be on drilled dimples for fitting the tool and through, or for other reason begins the principle of that at F. Here the screwing on the locknuts. A light to leak, removal can be effected by body contains a hard steel cone tap at the end of the shank indents making a central slit with a small operated by a draw bolt to expand a the balls. Then with the locknuts sharp chisel, and then levering the number of steel balls. Washers or tightened, the tool can be turned to plug out. Alternatively, three or collars outside the body allow for peen the metal over the chamfer on four holes can be drilled in line. adjusting working distance of the the seating. For fitting a new plug, the recess balls from the ends of tubes. q 29 JUNE 1961 801 MODEL ENGINEER