Bought a old military air hammer at a garage sale for $5. It had riveter heads which fit and some chisel heads that will work but the retainer will not go over them to hold them in. Need to machine them down to the profie of the riveter head. Very hard. Metal comes off in very thin strings red hot. Do I have the wrong equipment or is this something I can't do. It goes through carbide like crazy. Any other ideas?