I cobbled up this disc sander jig to clean up the edges of small circular workpieces. It consists of a sled that rides on a base fixed to the table. To build the jig, first make the base and sled from 3⁄4"-thick plywood about 5" wide. To determine the length for both pieces, measure the distance between your sanding disc and the front edge of the tool’s table, and add an inch or so. Saw a dado lengthwise down the center of each piece. Size a 1⁄2"-thick runner to fit the dado, terminating it 2" from the outer end of the base, and then glue it in place where shown. Glue a 2"-long stop into the outermost end of the sled dado. Size a “registration bar” to fit your table slot, and glue and screw it to the underside of the base, so that the base and sled both rest against the sander disc.
To use the jig, drive a 4d finish nail into the sled at the centerline, setting it back from the inner edge of the sled a distance equal to the desired circle radius. Clip off the head of the nail. Drill a 5⁄64"-diameter hole in the backside of your workpiece, and set it on the nail. Place the sled on the jig base, and slowly push it inward while rotating the workpiece. Continue until the stop hits the end of the sled runner, creating a smooth-edged, perfect circle.
