EE WAS PUNCHING HOLE,1/2"",IN RUBBER CONVEYOR BELTING USING AN ARCH PUNCH. EE STRUCK HIS LEFT HAND WITH A 3 LB SHOP HAMMER WHILE HOLDING THE ARCH PUNCH. HE STRUCK HIMSELF ON THE FIRST FINGER BE HIND THE FIRST KNUCKLE AND THE REAR AREA OF HIS THUMB, CAUSING SWELLING AND TENDERNESS.