jim rozen writes:

Machine tool bearing surfaces do not typically exceed more than a few
100s of psi transiently, and much less statically.

Except for the clamping action of a the tailstock casting
on the ram. I would say that pure ptfe is a poor choice
for that application.

If you mean the narrow longitudinal strip of the ram which is engaged by
the clamp, yes, you would leave that as bare metal. It's not a bearing
surface anyway.

Note that with a polymer bearing surface, you could create a negative
clearance on the ram vs bore. This would eliminate both play and stiction,
which are typically why you need a clamp at all.