Disc Sander Circle Jig

Rough-cut two circles 1/4" larger in diameter than the disc you want. Drill a 1/16" hole through the center of one disc, which will serve as a model for the hole-free disc. Clamp a block to the sliding bar so it will stop the bar's nail at a distance from the sanding surface equal to the desired radius of your circle. Slip the model disc's hole over the nail in the bar, and sand it to size by rotating and feeding it into the sanding disc until the stopblock contacts the jig's base. Attach the second roughed disc to the top of the model with cloth-backed carpet tape, and sand the second disc the same way you sanded the model.