While working on an upcoming article on different methods to create curved components, I needed to cut a large radius into a base of particle board. Most of the circle-cutting jigs I have around the shop are set for diameters less than 24″. I needed an instant circle jig for around a 23″ radius. It’s easy to do.
Build Your Own
Grab a piece of plywood that’s longer than the radius you need. Because I was using this setup to cut off 1/2″-thick particle board, I used a trim router with a 1/4″ upcut spiral router bit already installed – another setup that we have ready to go in the shop. I didn’t need a plunge base because I was working from edge to edge on the board, not starting somewhere in the middle of the base. Through the plywood drill a 1/2″ hole, which is where the router bit sticks through.
My router base has a few holes drilled through it because of some other work I’ve done in the past, so the next step is easy, too. Slip the router bit through the 1/2″ hole, try to center it so that it doesn’t touch an edge then drive a couple of screws through small holes in the router base to attach it to the plywood.
Measuring from the edge of your router bit, lay back the radius amount then drill a through-hole that slips over a pivot point on the particle-board base. I had previously located the pivot while drawing in the needed arc. Slip the instant circle jig over the pivot and slowly make the cut to produce a clean and accurate arc,