Just got a brand-new Jet bench grinder. I turned it on and it started vibrating wildly. Before I could flip the switch back off, the wheel cracked and jammed in the guard, stopping the motor cold. I also heard something go whizzing right by my head, I think a small chunk broke off and came flying out the back chute, bouncing off the wall.
Needless to say, I'll be taking advantage of Amazon's excellent return policy.