A CONTRACTOR MECHANIC WAS REPAIRING A TRACK ON A D6 DOZER. IN THE PROCESS OF INSTALLING THE MASTER LINK HE STRUCK THE PIN WITH A STEEL SLEDGE HAMMER CAUSING A CHIP OFF THE PIN. SHOULDER TO BE PRPELLED STRIKING EE STANDING 15' AWAY, INT HE RIGHT AIR BI UPS. THE FRAGEMENT BECAME IMPEDDED ABOUT 1"" DEEP.