Quote Originally Posted by Brian Kent View Post
As a part of a large candle-holder project I am making an 8-sided pyramid. I need to figure out the table saw blade angle for the miter-cuts. If you know how to do this, could you check my work?

I am using this calculator:
http://www.pdxtex.com/canoe/compound.htm

I started with the slope calculation. The pyramid is 9" across at the base, so the Horizontal Run is 4.5". The Vertical Rise is 18.75". The resulting slope is 76.5° (76.504 to be exact).

It has 8 sides so the included angle shows as 135°. That calculates to an end angle of 5.5° (5.522) and a bevel angle of 22° (21.84).

Does this seem reasonable, before I try it on lumber?
This is a fairly common problem. I have made octagonal bird house tops and slanting-side flower boxes using a BASIC program (I actually wrote!) as an "app" to do the math. That was a long time ago and I no longer have the program or the skill to write it. However, I have collected programs (better than mine) that do this math for woodworkers. An easy one to follow is from the Woodworkers Guild of Georgia, see http://www.woodworkersguildofga.org/...Calculator.htm Using this program with your 76.5 slope angle and 8 sides I get blade angle 21.8 and miter angle 5.72 (90-84.28).