EMPLOYEE WAS USING AN IMPPACT WRENCH TO TIGHTEN THE SECURING BOLT OF A SUPER NUT. THE SUPER NUT IS USED TO HOLD THE LARGE BOLTS FOR THE SPIDER ARM OF THE PRIMARY CRUSHER. AS HE TIGHTENED THE S ECURING BOLTS, THE LARGE BOLT BROKE LOOSE FROM HEAD OF THE BOLT AND THE BOLT FELL STRAIGHT DOWN CAUSING THE EMPLOYEE'S HAND TO BE CAUGHT BETWEENTHE IMPACT WRENCH AND A METAL LODGE ON THE CRUS