Radius Sanding Jig
Sanding an even radius on workpieces can be tricky, especially if you're doing it freehand. But you can take the guesswork out of this process in a hurry with this quick-fix jig. To use the jig, you'll need an oscillating spindle sander or a drum sander attached to a drill press.
On the edge of a piece of 3⁄4 " plywood, cut out a half circle that will accommodate your largest sanding drum, as shown, above. From the edge of this half circle, measure to a point 1⁄8 " short of the radius to be sanded, and bore a 3⁄4 " hole where shown. Now, glue a 3⁄4 " dowel in the hole. The accuracy of the jig depends on the dowel standing 90-degrees to the plywood, so leave the dowel long enough to check it with a square. After the glue dries, you can cut the dowel to a shorter length.
Next, mark the radius on the workpiece, and cut the curve just outside the line. Bore a 3⁄4 " hole at the center point of the radius and slip the workpiece over the dowel. Adjust the plywood so the sanding drum just touches the long edge of the workpiece. When the jig is positioned correctly, clamp it to the sanding table, turn the sander on, and rotate the workpiece into the drum to sand a perfect radius.
If you don't want to bore a hole completely through your workpiece, you can bore the hole halfway through the stock, and cut the dowel just short of this depth. For smaller workpieces, you'll want to use a dowel with a smaller diameter.
Or, for a workpiece where you don't want any holes visible, delete the hole in both the workpiece and the jig top, and rotate the workpiece on a nail head protruding from the jig table.
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