AFTER SERVICING A CAT 789B END DUMP, EE WAS TIGHTENING A BOLT ON THE REAR HUB WITH A 3/4"" BREAKER BAR. AS HE WAS APPLYING PRESSURE, THE BOLT ON THE HUB STRIPPED AND HIS RIGHT LITTLE FINGER WAS PINCHED BETWEEN THE BAR AND THE HUB. HE WAS THEN TAKEN TO HOSPITAL, AND TREATED FOR A LACERATION AND A FRACTURE.