Step 1: Cut the Luan

Cut a piece of 1/4" thick luan into an elongated oval. The circular end of the piece should be the same size as the router's base plate.

Step 2: Measure and Mark the Circle

Determine the radius of the circle you want to create on your work piece; measure and mark that distance from the center of the circle on the piece of luan. At the mark, drill a hole through the luan to act as a pivot point. The distance from the center of the circle to the pivot point on the end of the piece of luan should equal the radius of the circle you wish to create.

Mark the desired radius for your work piece on a piece of square 1/4" thick plywood (the same length and width as the work piece).

Step 3: Cut the Radius Curve

Remove the router's base plate, and screw the luan into place on the router.

Secure the luan's pivot point to the center of the piece of plywood with a small nut and bolt.

Use the router to cut out the radius curve drawn on the plywood.

Step 4: Clamp the Jig to the Work Piece

Using a drill and small screws, attach the two small blocks of plywood (each about 6" x 2" x 1/4") to either end of the curve cut on the plywood base.

To use the jig, clamp it down onto the work piece, positioning the curve on the plywood base atop the area on which you want to cut an identical curve. Pivot the router around the curve to cut into the work piece.