By Tom and Kay Benham, Contributing Editors, Lapidary Journal Jewelry Artist
If you need to make small, perfectly round cabs (1⁄2 inch or smaller), it can be difficult because the eye can't easily pick out imperfections in the smaller sizes. I've found that if you use the back end of a drill bit -- which is the same size as the desired final diameter of the cab -- for the dop stick and carefully grind up to it, the cab will be perfectly round. Be sure to preheat the end of the drill bit with a heat gun to assure good bonding of the dop wax. I have cut cabs down to 1⁄8" using this technique and it's particularly helpful when trying to cut a matched pair. The drill bit can then be used as a mandrel to make a perfectly fitting bezel for your cab!