TAPERED-STAVE Bowl Bill Wells Am Relatively New to Woodturning Blank; Using Fewer Will but Have Worked with Wood Most of Reduce the Wall Thickness I My Life

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TURN A TAPERED-STAVE Bowl Bill Wells am relatively new to woodturning blank; using fewer will but have worked with wood most of reduce the wall thickness I my life. That’s why I started turn- you will have when turning. ing segmented pieces right away—I Start your drawing with a had a shop full of lumber and no V-shaped cone angle like the left turning blanks. But rather than using image in Figure 2; I used 600. If you a typical segmented design compris- want a flatter design, use a larger ing small segments glued into rings, I angle; a narrower design, a smaller started making staved designs, which angle. Next, draw the top line, which are similar but with fewer pieces. I will establish the top diameter, and the began with vertical beveled-edge bottom line for the base diameter. staves, which are useful but limit your Now you need to find dimensions a 5" (13cm) stave length, so I used 5½" blank to having only vertical sides. and angles for the staves, as follows: (14cm). Neither stave length nor width Soon I moved on to bowl-shaped needs to be exact, as long as all staves designs, which require tapered staves Stave width are cut to the same dimensions. that form a conical blank (Figure 1). If you have drawn a full-sized top In this article, I’ll describe how to view, you can measure the stave width Miter and bevel angles design and build a tapered-stave bowl. directly from your drawing; otherwise, Calculation of miter and bevel angles The example project is based upon the it can be estimated by dividing the for a tapered-stave design requires some bowl shown in the opening photo, but circumference of the top (3.14 × diam- number crunching, which I have done I have included everything you need eter) by the number of staves. Since the and presented in Figure 4, a table of pre-cal- to make a project of your own design. top diameter of our example project is culated miter and bevel angles for various 8¾" (22cm), the circumference is 27½" cone angles and numbers of staves. Benefits (70cm). With twelve staves, the width • Economical—very little wasted material would be 2.3" (5.8cm), which is very Grain orientation • Staves cut smoothly along the grain close to the measurement I took from For this project, the wood grain runs • Requires only a dozen or so pieces, my drawing, 2¼" (5.7cm). around the bowl, and, depending on the compared to hundreds species, this can create a dramatic effect. • Finished piece displays only facegrain Stave length I used bubinga for the example project, Stave length can be measured directly but any kiln-dried, defect-free hardwood Design and plan from your full-sized drawing; add ½" can make beautiful bowls. To achieve All segmented designs begin with a (13mm) for trimming. Figure 3 indicates this grain orientation, each stave will drawing, and stave designs are no excep- have the grain running across its width, tion. I use a software program, but all you not along its length. So you will be cross- need is ¼" (6mm) graph paper, a ruler, Two stave designs cutting your board to achieve the stave and a protractor. Make your drawings full width and ripping to achieve the stave size so you can use them later to easily length. This is opposite from most wood- determine stave dimensions. working applications, where you cross- See Figure 2 for terminology used cut a board to length and rip it to width. in this article and Figure 3, the design Your board should be at least ¾" drawing for the example project, (19mm) thick; the thickness determines showing all dimensions and angles. how much material you will have to work First, choose the number of staves for Figure 1. Basic-stave design, left, is with when turning. I used a 36"- (91cm-) straight-sided; tapered-stave design, your bowl. I used twelve staves, which right, is cone-shaped. long board, 5½" wide, which was plenty is enough to produce a decent turning for the twelve staves plus two extras.

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Terminology & Sample Specs

Figure 2. Terminology of tapered stave design. Note that I use the term Figure 3. Dimensions and angles for the example project. This is a CAD cone angle—other resources might use side incline angle, which is half drawing, but a hand drawing will work just as well. the cone angle.

Table saw sled Staves 4 6 8 10 12 Much has been written about the need Cone angle Miter Bevel Miter Bevel Miter Bevel Miter Bevel Miter Bevel for absolute precision when cutting seg- 0 0.0 45.0 0.0 30.0 0.0 22.5 0.0 18.0 0.0 15.0 ments, and staves are a kind of segment. 10 5.0 44.8 2.9 29.9 2.1 22.4 1.6 17.9 1.3 14.9 20 9.9 44.1 5.7 29.5 4.11 22.1 3.2 17.7 2.7 14.8 The most critical thing is to make every 30 14.5 43.1 8.5 28.9 6.1 21.7 4.8 17.4 4.0 14.5 stave identical—same miter, bevel, width, 40 18.9 41.6 11.2 28.0 8.1 21.1 6.3 16.9 5.2 14.1 and length for each. But you don’t have 50 22.9 39.9 13.7 26.9 9.9 20.3 7.8 16.3 6.5 13.6 to use a micrometer to measure stave 60 26.6 37.8 16.1 25.7 11.7 19.4 9.2 15.5 7.6 13.0 70 29.8 35.4 18.3 24.2 13.4 18.3 10.6 14.7 8.7 12.2 width and length; rounding up to the 80 32.7 32.8 20.4 22.5 14.9 17.0 11.8 13.7 9.8 11.4 nearest fraction is OK, as long as you use 90 35.3 30.0 22.2 20.7 16.3 15.7 12.9 12.6 10.7 10.5 the same dimension for each stave. You 100 37.5 27.0 23.9 18.7 17.6 14.2 14.0 11.5 11.6 9.6 110 39.3 23.9 25.3 16.7 18.7 12.7 14.9 10.2 12.4 8.5 do need to set angles for miter and bevel 120 40.9 20.7 26.6 14.5 19.7 11.0 15.7 8.9 13.1 7.4 precisely, and below I discuss ways to do 130 42.2 17.4 27.6 12.2 20.6 9.3 16.4 7.5 13.6 6.3 this. But don’t worry; there is a fix if your 140 43.2 14.0 28.5 9.8 21.3 7.5 17.0 6.1 14.1 5.1 angles are off slightly. 150 44.0 10.5 29.1 7.4 21.8 5.7 17.4 4.6 14.5 3.8 160 44.6 7.1 29.6 5.0 22.2 3.8 17.7 3.1 14.8 2.6 To cut the tapered segments, I made 170 44.9 3.5 29.9 2.5 22.4 1.9 17.9 1.5 14.9 1.3 a simple sled from ¾" plywood, with a 180 45.0 0.0 30.0 0.0 22.5 0.0 18.0 0.0 15.0 0.0 hardwood runner underneath that slides Figure 4. Table of miter and bevel angles for cutting tapered staves. Numbers used for the example in the table saw’s miter slot (Photo 1). The project are highlighted. key is to start by making the sled over- sized, so that the left edge extends past the blade by an inch (25mm) or so. When Table saw sled you have completed the rest of the sled, raise the blade and push the sled through to trim off the overhang. This will make the left edge of the sled exactly parallel with the saw blade; now the left edge can serve as a reference for laying out angles. Use a 4"- (10cm-) wide piece of 1 2 The author’s shopmade table saw sled The saw is set up for cutting staves. An plywood for the fence; be sure the top for cutting tapered staves, set for a miter adjustable stop block, at left, ensures each edge is smooth and straight. I used a angle of 7.6°. Since the digital protractor stave is cut at identical width. The saw digital protractor to set the angle of the is aligned with the left edge of the sled, its blade is tilted to the required bevel angle, angle is set to the complement of the miter in this case, 13°. fence to the miter angle, in this case, angle: 90°-7.6° = 82.4°. 7.60. Drive the left screw first, tap the

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3 4 The ends of staves must also be beveled so they will sit flat when assembled into a cone. Set the saw blade’s bevel to one-half the cone angle—in this case, 30°. 5

fence till you get the angle you want, and beveled end, then turn the board the fence. Trim away until the top edge is and then drive the other screws. over and cut your first stave. After each beveled, as in Photo 4, and make a mark I also made an adjustable stop to stave is cut, the board is turned over on the sled at the small end of the stave ensure cutting accurate stave width. and the next stave cut. Each time you to indicate where to place the remaining Your stop does not need to be adjust- turn the board and cut, the stave will staves when you cut them. Now do the able, but it is essential to have some have the correct miter and bevel. same to the bottom edge of the stave, but kind of rigid stop for consistency. trim with the narrower side up. To set the blade bevel (some call this Bevel the stave ends blade tilt) to 130, I use a magnetic digital After all staves have been cut, the ends Get ready to glue angle gauge. Photo 2 shows the saw set have to be beveled so that, when assem- It is awkward to glue and then clamp up for cutting staves. The blade is tilted bled, the staves will sit flat yet the staves together a dozen angled pieces. It helps at the bevel angle, the fence is set at the will splay outward and the top rim will greatly to have a set of custom-made miter angle, and the point of the board is be horizontal, as shown in Photo 3. You cauls to keep the staves in a conical shape. against the stop to set the width. The stave can use the same sled as in the previous I made twelve cauls, one for each stave length is predetermined by the width of step, but re-set the saw blade’s bevel to (Photo 5). It helps to do a dry fit-up prior the board, which has been ripped to 5½". one-half the cone angle. For the example to gluing. Lay all your staves out in a fan To start, trim away the square end project, I set the bevel to 60 ÷ 2, or 300. pattern, wider side up and tape the staves of your board to establish a mitered Now set the stave, wider side up, against together with blue painter’s tape (Photo 6). Then move the taped-up staves into a cone shape, set it on a work surface, and Dry-fit the assembly Glue the staves add the cauls and rubber bands (Photo 7). Notches in the cauls provide a place for rubber bands to grip, and the compres- sive force of the bands is directed inward. Make these, or something similar, before gluing. You will be glad you did. 8 6 Next, separate the staves into two equal groups. You are going to glue up these two groups separately but at the same time. Keep each group securely taped and put a narrow strip of double- sided tape on the two edges that won’t be glued. This way, you will end up with 9 two separate halves of your bowl blank. 7 Apply a liberal amount of wood glue Apply plenty of wood glue in the Tape the staves into a fan pattern and and clamp with rubber bands. Two dry-fit them prior to gluing. Cauls and opposing joints are not glued yet, valleys between the staves (Photo 8). rubber bands hold the staves in place. forming two halves of the bowl blank. Now gather everything together and set the cone big end down on your

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work surface, with the cauls in place, my bandsaw, then sanded it smooth to work with. Changing to a ⅜" (10mm) and stretch rubber bands to keep the and flat. I used a disc sander to sand bowl gouge, I turned the piece to its final assembly together. Now is the time to the mating face of the stave assembly shape, with slight contours at the base and make sure the glue joints are aligned. (Photo 11). Make sure the two pieces top (Photo 13). If you start with thicker Add several more and tighter, heavy mate without gaps, then glue and material, you will have more flexibility rubber bands. Photo 9 shows the staves clamp the two pieces together. I use a with regard to your bowl’s final shape. glued and clamped. Let dry overnight. shopmade press for clamping (Photo 12), but other clamping methods, or Sanding and finishing Unbundle and check fit even using weights, will work. I typically start sanding with 120- You now have two similar halves. Butt As you see in Photo 12, I also glued a grit abrasive and progress to 800 grit. them together and, alas, the edges will waste block to the base for mounting on A staved piece sands nicely because not fit perfectly flat. This is normal; after a faceplate. Let the glue dry overnight you are sanding along the grain on all, you made several compound-miter before proceeding to the next step. each segment. To finish this project, I cuts, so any slight variation in accu- applied three coats of shellac, rubbing racy would be magnified across all the Finally, ready to turn! with 0000 steel wool between coats. staves. To get the mating edges to fit flat Mount the blank onto your lathe and After parting the bowl off, I wrapped together, sand both halves face down on rotate it by hand. It will be somewhat foam tape around the remaining base a smooth sanding board (Photo 10). I use out of round, as would be a solid-wood and waste block and held the bowl in 120-grit abrasive glued to MDF. blank. I use a ½" bowl gouge to rough- place with the live center in the tailstock Now glue the two halves together, using turn the outside, starting at a slow for completing the base (Photos 14, 15). the same procedure as in the previous step. speed, and use the same tool for the interior. Except for the base, you will Bill Wells is a retired engineer living in Make and glue the base be cutting entirely along the grain, Olympia, Washington. He has worked with wood in one way or another most of his For the example project, I made the which will likely be smooth going. life and is now a member of Woodturners base from a piece of ¾"-thick walnut, After truing the bowl round, I had a of Olympia, an AAW chapter. Bill welcomes 5" square. I cut the base round on little over ½" of uniform wall thickness comments at [email protected].

Flatten Glue on base Sand the bottom remaining edges smooth and flat prior to gluing on the base. I use a shopmade fixture to apply pressure, but an F clamp with a deep enough throat would also work. 10 Sand to flatten the mating edges of each half yet to be glued. 11 12

Turn the bowl Turn your tapered- stave bowl. Foam tape is wrapped around the remains of the base and waste block to form a jam chuck for completing the 13 14 15 bottom.

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