Best PTFE. for rings Virgin or filled, carbon/grahite

[ChinkoaParticipant @chinkoa]

Which is best PTFE. for inlet Steam Bobbins rings. Virgin, Filled Carbon PTFE, or Graphite filled PTFE?

For the amount of use it will get I am leaning towards the Virgin variety.

What sizes and clearances for a 15/16 Dia. Bore? Diameter, Width and thickness.

I am thinking of fitting two rings insame groove and making the total width the same as the inlet port (1/4&quot 2 x 1/8" wide rings.

Colin

[ChinkoaParticipant @chinkoa]

Rings for inlet Steam Bobbin

[Simon CollierParticipant @simoncollier74340]

That is a vexed issue. The high expansion of PTFE with temperature is very problematic. The bore needs to be honed to a very good finish or the PTFE will wear very quickly. Fluoroscint, which is mica filled I think, would be my pick but it is very expensive. It's thermal expansion is 1/3 that of virgin and in the order of that of aluminium. If at all possible, I would use conventional valve rings.

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