EMPLOYEE STATED THAT THE OPERATOR WAS TURNING A 90 DEGREE TURN TO THE LEFT. THE VICTIM WAS ROOF BOLTING ON THE OPERATOR SIDE & WAS INSTALLING A DRILL STEEL IN THE CHUCK SO THAT THE MINER COULD SEE WHEN TO PUT IN A CORNER BOLT. WHEN HE WAS BACKING OUT FROM PUTTING THE DRILL STEEL IN, THE RIB PROTECTOR CAUGHT A NOTCH IN THE RIB CAUSING THE PROTECTOR TO SWIVEL AROUND STRIKING EE.