How to Choose a Bronze Bushing Material: C93200 vs C93700 vs C95400

The short version: C93200 for everyday bearings, C93700 where dirt and poor lubrication are normal, C95400 where loads exceed what tin bronzes carry.

Why lead is in bearing bronze

The classic bearing bronze recipe is copper plus tin plus lead. Tin hardens the alloy; lead does something subtler — it exists as soft particles that act like a dry lubricant and, more importantly, let grit bury itself instead of cutting the shaft. A bushing carrying dust and shock loads without lead in it soon becomes a shaft-scoring machine.

That trade-off matters more than the strength numbers when you are choosing.

C93200 (SAE 660) — the default

Copper 81–85%, tin 6.3–7.5%, lead 6–8%, zinc 4–7%. It is the most common bearing bronze in the world: strong enough for the vast majority of industrial bushings, easy to machine, and its lead content swallows ordinary levels of contamination. If you are replacing a bushing and nobody specified an alloy, C93200 is the safe default.

C93700 — for the dirtiest jobs

The lead climbs to 9–12% and tin to 9–11%. More lead means more embeddability and better seizure resistance under shock and boundary lubrication; it costs strength and machinability. This is the alloy for crusher socket liners and mining bushings where oil is marginal and grit is everywhere.

C95400 — when the load wins

Aluminum bronze: copper 83–87%, aluminum 10–11.5%, iron 3–4.5%. Roughly twice the strength of tin bronzes, seawater corrosion resistance, and it keeps strength at elevated temperature. It is harder, so it needs reasonably clean, aligned, lubricated service — put it where tin bronze would break, not where it would wear.

A simple decision path

Dirty service, marginal lubrication → C93700. Normal industrial service → C93200. High load, hot, or seawater → C95400. When in doubt, send us the duty: load, speed, lubrication, environment. We pour all three alloys daily and will recommend the one that survives.