EMPLOYEE WAS WORKING AT THE SHOP TAKING BOLTS OUT OF THE FACE PLATE TO THE BOOSTER PUMP TO REMOVE THE WEAR PLATE. EMPLOYEE WAS ATTEMPTING TO LOOSEN A BOLT, PUSHING THE WRENCH AWAY FROM BODY WHEN THE WRENCH SLIPPED OFF THE BOLT AND THE TOP OF RIGHT INDEX FINGER STRUCK ANOTHER BOLT PROTRUDING OUT OF THE FACE PLATE RESULTING IN A LACERATION.