On Sat, 08 Oct 2005 18:28:57 -0700, Jon Anderson
wrote:

Doing some new parts for a new customer. A few of his parts, he doesn't
have drawings for, as they are purchased from the manufacturer of the
equipment he buys, modifies, and resells.

I have two bushings to make out of plastic, he doesn't know exactly what
they are made of. I thought MDS until I compared a sample to the
bushing. MDS from McMaster at least, is a sort of gray color and quite
hard compared to the sample. Sample part is a very dark charcoal black,
and under a microscope it looks like microscopic pits tear out of the
material in machining. Also seems to have very minute reflective flakes
impregnated throughout. It feels like Teflon, and a trial part I made in
Teflon has the right "feel" on the mating shaft. Both materials seem to
be about the same hardness. I know about Delrin AF, and it's certainly
not that.

I've never seen a black Teflon before. Almost like graphite filled...
Ring any bells?

Thanks,

Jon

It exists. Google it.

I tried to use bronze filled teflon for a seal once. What a disaster.
It came highly recommended, but the thermal expansion was much greater
than the tool steel it was to seal. It invariably buckled out of its
groove and jammed. Silicone elastomer did the trick.

Pete Keillor