ROTARY HEAD IN THE DRILL MAST WAS NOT SECURE PRIOR TO WORKING ON THE BROKEN CHAIN. WHEN EE STARTED RAISING THE BROKEN CHAIN WITH A MANUAL COME ALONG, THE ROTARY HEAD SHIFTED AND DROPPED. HE WA S STRAPPED IN A SAFETY HARNESS, BUT WAS SHOCKED BY THE SUDDEN MOVEMENT AND GRABBED THE CHAIN WHICH DREW HIS HAND INTO A PROCKET, INJRING HIS FINGERS.