WHILE WORKING ON AN AIR LUBRICATION PUMP ON A WORK BENCH IN THE REFUSE SHOP, EE'S LEFT THUMB WAS SEVERED BETWEEN THE BOTTOM OF THE NAIL & THE 1ST JOINT. WHEN AIR WAS APPLIED TO TEST THE PUMP, THE PISTON STROKED, CUTTING THE END OF HIS THUMB WHICH WAS INADVERTENTLY IN THE CHAMBER.