ELECTRICIAN & HELPER WERE WORKING IN THE SURFACESHOP, ATTEMPTING TO REPAIR A PUMP. THEY WERE USING A 48""PIPE WRENCH TO TIGHTEN A FITTING INTO THE DISCHARGE END OF PUMP. EE WAS STEADYING THE WRENCH AS CO-WORKER APPLIED PRESSURE TO WRENCH USING HIS ENTIRE BODY WEIGHT. THE PIPE WRENCH SLIPPED OFF OF THE FITTING & PINCHED EE'S FINGERBETWEEN THE WRENCH AND THE FLOOR.