For example, JUST FOR FUN CM CA3 PDF a straight eight sided cylinder, the pieces need to be bevelled at 22. But when the cylinder is tapered, that same 22. I knew about the problem, but hadn’t had a reason to work out the math for it so far. Looking around the web, I couldn’t readily find a site that already had it worked out, so I thought it might be a fun thing to cover on this site.

I worked out the math for it. A number of people have asked about the math for the claculations. I worked it out on paper, and then made a Sketchup drawing to verify my calculations. I also typed the formulas into the Sketchup model so I wouldn’t lose them. You can enlarge the image at left to for a better view. To try my calculations on a real workpiece, I made an octagon, tapered by 30-degrees.

But looking at it along the joint, that 45 bevel gauge set to 45 degrees no longer fits the joint. The more the shape is tapered, the closer to 90 degrees the miters become. I had cut the test pieces using my miter saw. But I’m really no fan of using a miter saw, especially for small pieces, where it’s difficult to secure the workpiece against the low fence. For my second piece, I went back to using the table saw. Miter saws are also very dusty. For my next piece, I chose ten sides, and a 40-degree taper angle.