A client has asked me to build a fixture for his artwork. This fixture will be a panel 5' x 5' x 6" deep. It needs to have a spiral groove approximately 1" wide x 1 1/2" deep cut into the face of the panel, starting in the center and rotating out to the edges. Any ideas on how to go about cutting a spiral groove cleanly?
Find a shop with a point to point or CNC router. Try calling the tools sales places in your area--they should be able to help you locate a shop with one.
To do it yourself I'd suggest the following (try this on scrap first).
Take a 3" to 4" high cylinder of about 2" diameter (pvc pipe would work well). Secure it to the face of the board in the center of the spiral. Take a router and connect a cord from it to the spiral. As you move the router around the cylinder (I believe in a counter-clockwise direction and keeping the cord taut), the cord will wrap around the cylinder, continually shortening the distance between the router and the cylinder. Voila, a spiral groove.
You will of course have to experiment a bit to come up with the right cord length and cylinder diameter. But you should be able to make it happen.