Set your circle cutter without calculating

I used to dread using my adjustable circle cutter: I had to figure the radius of the circle (halving odd diameters like 3-⁷⁄₁₆ " brought out the calculator), then fuss with a ruler, the pilot bit, and cutter to set that radius. It was a pain in the neck and required a lot of tweaking.

To eliminate the headaches, I devised the simple fixture, shown in the illustration at the bottom of the page, with a half-scale ruler built right in. After drawing the half-scale on my CAD system, I printed it (you can use the full-size pattern shown below) and had it laminated at an office-supply store. Then, I attached it to the jig with double-faced tape.

If I need a 3-⁷⁄₁₆ " circle, I simply insert the pilot bit into the ¹⁄₄ " hole in the riser block, extend the cutter to the 3-⁷⁄₁₆ " mark on the half-scale, and lock it in. When I'm done, the cutter and its hexhead wrench store in the jig as shown below.
—Bob DiTucci, Wayne, N.J.