EMPLOYEE WAS TAKING BOLTS LOOSE ON THE LINER OF THE PUMP WITH AN 1 5/8"" WRENCH, PUSHING DOWNWARD WITH BOTH HANDS. THE WRENCH SLIPPED OFF SENDING HIS HANDS DOWN AGAINST THE NEXT BOLT BELOW, SMA SHING HIS MIDDLE FINGER. HE WAS WORKING UNDER HURRIED CONDITIONS AND WITHOUT GLOVES ON.