I tried using a round rasp but was never able to get that nice even cup.
Now I do it right on the lathe. Instead of cutting the plug off flat I angle in as far as possible with the cut off tool then finish the inside with the small home made tool in the photo. All I have to do to finish is nip out the tiny bit left in the center with a small carving gouge.
Photo #1 - the tool with the turned blank
Photo #2 - the finished plug
|