EE HAD THE TASK OF REMOVING PARTS FROM A 3406 CAT D8N ENGINE. IN REMOVING PART FROM THE CYLINDER HEAD, EE HAD A PROBLEM WITH THE BOLTS SECURING THE TURBO MOUNT TO EXHAUST MANIFOLD. THE NUTS WE RE NOT HEAT RESISTANT AND HAD ROUNDED OFF. EE MADE THE DECISION TO USE A CHISEL. EE HAD ALMOST FINISHED THE CUTTING, WHEN HE MISSED CAUSING THE CHISEL TO HIT HIS L THUMB AGAINST MANIFOLD, CUT