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wrote:

Trevor Jones--

Thanks for your comments--my last auto engine rebuild was over 30 years
ago--guess thing change.;-))

Tut

Things have not changed that much in that time.

Cylinders get bored using a boring tool, The bores are sized to fit the
pistons, not the other way around. Odds are good that your local engine
rebuilder is using the same machine he was using 30 years back. The
bores are then honed with abrasive stones to provive a finish.

About the only part of the engine rebuild process that may involve
lapping, is the final seating of the valves to the valve seats. Even
that is more of a shade tree mechanic thing, as the pro's tend to get
good seal using their proper tools in good shape.

I think it's fair to say that abrasive finishing of nylon is a
non-starter. Any abrasive that can cut into the nylon will produse a
vast multitude of stringy threads and a rough surface, not conducive to
sealing the piston. Any loose abrasive, such as lapping compound, will
embed itself into the nylon and provide you with a quite effective way
to destroy the cylinder of the air rifle.

Suit yourself, though.

What make of air rifle? Chinese? European? American? Parts are readilly
available for many makes, and cheaply, too. Not as much fun as building
your own, but the chance of success is greatly increased.

Cheers
Trevor Jones