Hi Bill,  Thanks for the info.  A few people have replied already and
their letters have been forwarded to the MMD.  I will also forward
yours as it contains some information that the others did not have.

Thank-you,

John A. Tuttle

 - - -

John,  Delrin is a DuPont plastic very similar to nylon.  Specifically
it is a polyimide / polyamide copolymer.  As I remember it was first
marketed in the 60's (this date may be wrong it is just as I remember it).

Delrin is available in blocks that can be machined.  It is much easier
to machine than aluminum (or certainly steel).  It is used for making
silent gears (like camshaft gears on autos).  It is very hard and self
lubricating in some applications (a little like Teflon in that
respect).  It is a popular material for small production run mechanical
objects.  I suspect that it is available as rods which could be cut to
form the pistons you refer to.  Delrin is not electrically conductive.

Regards,

Bill Finch