OUR EXPERIENCED TIRE MECHANIC WAS REPLACING THE INSIDE DUAL TIRE ON A CAT 785 HAUL TRUCK WHEN THE SNAP RING SLIPPED FROM HIS HAND & CAUGHT THE TIP OF HIS RT. RING FINGER BETWEEN THE RING & THE WHEEL. THE INJURY WAS TO THE FLESH ON THE BOTTOM OF HIS FINGER. EE WAS TAKEN TO AN E.R. WHERE THE WOUND WAS CLEANED & HE WAS GIVEN A PRESCRIPTION FOR PAIN MEDICATION.