resizing ptfe rod

[Peter Fairbrother]

I have need of some ptfe rod of about 8mm diameter. The exact diameter
doesn't matter, but it has to be the same within a couple of 1/100mm. I
will more of it in future, ie I need a continuing supply.

When I buy ptfe rod it is typically oversize, eg nominal 8mm is maybe
8.6 to 9.0mm dia. If I could resize it to say 8.50 +/- 0.002mm that
would be great, but I need meters of it, far too much to resize by
turning down on a lathe.

Any ideas?

Ta

Peter Fairbrother

[David Billington]

Hi Peter,

    That's a tight tolerance considering the high expansion coefficient
of PFTE, much temperature change and it'll be out of spec.  My
suggestion though would be what I made some years back for a job I do
from time to time turning parts out of acetal bar and the same problem
with the rod being over the size required, basically a travelling steady
with ball bearing tips to support the rod and a turning tool built in
right next to the rollers, in my case I mount it in the toolpost and run
it down the rod. Maybe you could mount something similar in a vice and
feed the rod through using a drill to turn it. Food for thought maybe.

[David Billington]

Just occurred to me that travelling steadies usually have 2 supports,
the one I made has 3 at 120 degrees apart so it looks like a fixed
steady with roller tips.