EMPLOYEE WAS ASKED TO BRING A CAN OF OIL TO ROOF BOLTER AFTER PUTTING OIL IN ROOF BOLTER OPERATOR OF ROOFBOLTER STARTED BACK TO BOLT TOP. HE DIDN'T SEE EMPLOYEE HAD LAID HIS HAND ON BOLTER, WH EN HE SWUNG HEAD TO ONE SIDE IT CAUGHT EMPLOYEE'S FINGER AGAINST FRAME OF BOLTER.