C93200 Bearing Bronze (SAE 660) — Leaded Tin Bronze for Bearings, Bushings & Wear Plates

ASTM B584 (UNS C93200, SAE 660) · Published: 2026-06-14 · Updated: 2026-06-17

C93200 (SAE 660) is the most commonly specified bearing bronze worldwide. Its 7% tin + 7% lead + 3% zinc + balance copper composition creates a microstructure of hard copper-tin dendrites (the load-bearing phase) embedded in a soft lead-rich matrix (the lubricating phase). When the bearing runs, the lead phase smears across the surface, providing emergency lubrication if the oil film breaks down. This self-lubricating characteristic is what makes C93200 forgive the kinds of intermittent lubrication failures that would seize a steel-on-steel bearing instantly.

The 6-8% lead content is what differentiates C93200 from non-leaded bronzes like C90500 (tin bronze, no lead) or C90700. The lead provides machinability (C93200 machines at approximately 70% of free-cutting brass — excellent for a bronze) and embeddability (the ability to absorb hard dirt particles into the bearing surface rather than letting them score the shaft). For applications in food processing or potable water where lead is prohibited, substitute C89835 (bismuth-tin bronze, ASTM B584) — but expect approximately 15-20% shorter bearing life and higher shaft wear.

Key applications: general-purpose sleeve bearings, pump impeller wear rings, thrust washers, worm gears, bridge pins, and marine shaft bearings. Not recommended for: high-speed applications above 500 SFM (surface feet per minute), operating temperatures above 230°C (450°F), or highly corrosive environments — use C95400 aluminum bronze or C95500 nickel aluminum bronze for these conditions.

Global Equivalents & Cross-Reference