INJURED EMPLOYEE WAS ATTMPTING TO MACHINE A HUB IN THE METAL LATHE IN THE MAINTENANCE SHOP. THE HUB HAD A LIP THAT PREVENTED THE JAW OF THE CHUCK TO HAVE FULL CONTACT WITH THE PIECE. AS HE S TARTGED THE LATHE, THE CUTTING TOOL CONTACTED THE HUB AND EJECTED IT INTO HIM, RESULTING IN A LACERATION ON HIS CHIN THAT REQUIRED FOUR STITCHES.