Abstract: At approximately 3:00 p.m. on May 16, 2006, Employee #1, a maintenance mechanic, was using a Central Pneumatic .25-in. die grinder fitted with a 4-in. abrasive-impregnated, fiber reinforced, cut-off disk to remove damaged threads from the end of a bolt. Employee #1 was holding the bolt in his left hand and bracing the bolt against a lathe table while he used the pneumatic die grinder that was in his right hand. While he was cutting the bolt, the disk shattered, throwing disk fragments into his chest. Employee #1 collapsed and was bleeding profusely from the chest injury. The grinder was not guarded as required. Employee was hospitalized.