A little bit of chamfering

Your plan for the Optical Illusion Cutting Board in issue 266 (March 2020) suggests using a chamfer bit for spot-on 45° cuts. But the one I bought wouldn’t chamfer the full thickness of the 3⁄4" workpiece. I went ahead and cut the 45° bevel on my tablesaw, but it wasn’t perfect. So, if I make another cutting board like this, what size chamfer bit should I get?

—Ron Wientjes by email

Think back to your high-school geometry, Ron, and remember that both legs of a 45˚ right triangle are equal length. Applied to router bits, if you want to completely chamfer the edge of a

3⁄4" thick workpiece to 45˚, you need a bit with a radius at least 3⁄4" larger than its guide bearing. The CMT 836.950.11 bit I used measures 29⁄16" in diameter, which, when you subtract the 1⁄2" bearing, leaves a little over 1" radius for cutting, so it will chamfer a board up to 1" thick.

You can buy the CMT bit at amazon.com by searching for the model number, or by pointing your smartphone’s camera at this code. The Freud 40-118 and Whiteside no. 2310 also have sufficient cutting capacity.

John Olson, Design Editor