HE WAS CHANGING SHAFTS AND HANGER BEARINGS ON #2 SCREW. TOOK OUT BOLTS THAT HOLD SHAFT TO SCREW. PUT PIPE WRENCH ON SHAFT THEN TURNED ON MOTOR TO BREAK SHAFT LOSE FROM SCREW. THE SCREW CAME OU T OF PAN HITTING HIM IN THE RIGHT ARM AND PUSHED HIM INTO GUARD RAIL, HITTING HIS LEFT SIDE.