EMPLOYEE STATED HE WAS DRILLING A ROOF BOLT HOLE IN AN AREA THAT HAD BEEN CUT FOR OVERCAST DEVELOPMENT. THE AREA HAD OLD BOLTS EXPOSED IN THE ROOF. WHILE DRILLING THE HOLE HIS DRILL HEAD CONTACTED THE BOLT & IT BROKE. WHEN THE BOLT BROKE IT FEEL ON THE ROTATING DRILL HEAD & THEN STRUCK THE EE IN THE MOUTH.