EMPLOYEE WAS INSTALLING A ROOF BOLT AND ACCIDENTLY STRUCK THE BOOM LEVER CAUSING IT TO DROP DOWNOFF THE BOLT. HE THOUGHT THE BOLT WAS GOING TO SET UP AND HE USED HIS RIGHT HAND TO MOVE THE BOLT OVER FOR ALIGNMENT. AT THE SAME TIME HE APPLIED UP PRESSURE TO THE DRILL POD AND HIS RIGHT MIDDLE FINGER WAS CAUGHT BETWEEN THE PLATE AND ROOF. THE TIP OF FINGER BEHIND NAIL WAS SEVERED.