PTFE Rods for Bush Manufacturing

Why PTFE for bushes

A bush machined from PTFE rod runs dry. With a coefficient of friction between 0.05 and 0.10 — the lowest of any solid material — a PTFE bush needs no oil or grease, which is exactly what you want in food, pharmaceutical, chemical and cleanroom equipment where lubricant contamination is unacceptable, or in sealed assemblies that can never be re-lubricated. It will not swell in wet or humid conditions the way a nylon bush does, so the running clearance you machine is the clearance you keep. And because PTFE is chemically inert, the bush survives in acids, caustics and solvents that would destroy metal or other plastic bearings.

Virgin vs filled PTFE for bushes

Virgin PTFE gives the lowest friction and best chemical resistance, but it is soft and creeps under sustained load. For a lightly loaded, slow-moving or chemically-exposed bush, virgin PTFE rod is ideal. For higher loads, higher speeds (PV values) or where wear life matters, a filled grade — glass-filled, carbon-filled or bronze-filled PTFE — trades a little friction for a large gain in load capacity, wear resistance and dimensional stability. Tell us the shaft diameter, load and speed and we will confirm which grade to machine from.

Machining and fitting tips

PTFE machines cleanly on standard lathes with sharp tooling, but it has a high thermal expansion coefficient, so allow for it: a bush cut to a tight interference fit at room temperature can seize when the assembly heats up. Machine the bore to the running clearance recommended for the operating temperature, not just ambient. PTFE also cold-flows, so for a press-fit bush a metal backing sleeve or a shouldered housing prevents the bush creeping out of position under load.

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