An employee was fabricating a mount for a conveyor cylinder when he discovered a burr on the short side of a 3-inch by 5-inch piece of metal. He moved to the pedestal disc grinder to remove the burr (still wearing his welding gloves), put the metal down on the rest, and pushed it against the disc. The downward motion of the disc caused the metal to flip up. His right thumb contacted the disc and was pulled down between the grinding disc and grinder rest, suffering an avulsion.