My vise needed some balls for holding non parallel pieces. I saw this somewhere on the net along with using copper wire or aluminum wire at the moveable jaw to allow clamping to a flat side when dealing with rough parts.
Both work but I keep loosing my wire! Any how, since I just finished my tool and cutter universal grinder I thought I would try it out.
Chucked up the 1" ball bearing in a 5C collet, mounted that on the grinder table and went to work. Here is the result. The flat is visible on the ball on top of the piece of brass.