North Mains MMU 003 at 35 block, approx. 50 ft in cross-cut 5 to 4. the operator was making a clean up pass with only his bits and scrubber running loading a s/c. There was a frictional ignition in the left corner of the face, the flame was orange in color with smoke after the flame went out flame lasted 1 to 2 seconds. no injuries.