EE REMOVED GUARD TO TRAIN BELT AT SCREW TAKEUP. AFTER BELT TRAINED BELT WAS SHUT OFF. EE #2 ENT TO INVESTIGATE WHY JAW CRUSHER WOULD NOT START AND TOLD INJURED EE THAT HE WOULD WORK ON IT. START SEQUENCE REQUIRES CONVEYOR BE STARTED FIRST AND WHEN EE PUSHED START BUTTON HEARD YELL AND PUSHED STOP BUTTON. EE 2 WENT TO HELP INJURED GET ARM FREE FROM PULLEY BY CUTTING BELT AND REMO