For you guys who have a grinder. If your machine starts shocking you with what seems to be static shock, run a small wire from the base or a metal part to the ground (the earth itself). This should stop it if it's static.
If you're sure enough getting shocked, you may need to take an airhose and blow out the windings of the motor. Steel dust can build up and short across and do funny things. Sealed motors would, of course, be less likely to have this problem.
Lin