the piston pin to replace with a new not only the gaskets and o-rings and also the oil and dirt seals on the front where the striking pin is that must be absolutely not air leaking because all your work burns in a few months again out . you can start all-over again.
a vise is a must (do a safety goggles) hard steel on hard steel can deliver hot splinters at this job, put it the chisel with the machine fixed cross in a vice place the chisel lock on the machine open and slam a fist hammer slowly machine of the tool down.
why cant i get my drill bit 