Using a diamond tapered bead reamer from Widget Supply. About 60 cents each for the 1/8 inch style. And less for the 1/16 inch type.
The 1/16 inch style works well for beads made on a 1/16 inch SS mandrel that are in the range of 9 mm OD by using a hand reamer.
http://www.widgetsupply.com/product/BCZ32.html