C93200 vs C93700: Which Bearing Bronze Is Right for You?

When it comes to bronze bushings and bearings, C93200 and C93700 are the two most commonly specified alloys. Both are leaded tin bronzes designed for bearing service, but they serve different niches. Choosing the right one can mean the difference between a bearing that lasts for years and one that fails prematurely. Here's how they compare.

Quick Comparison

C93200 (SAE 660) is the general-purpose workhorse — the most widely used bearing bronze in the world. It offers a balanced combination of strength, wear resistance, and machinability at a competitive price. C93700 (SAE 64) is the high-lead variant, formulated for heavy loads and low speeds where conformability and embeddability are critical.

Composition Differences

Both alloys are copper-tin-lead bronzes, but the lead content is the key differentiator. C93200 contains 6-8% lead and 6.3-7.5% tin. C93700 increases the lead to 8-11% while maintaining 9-11% tin. The higher lead content in C93700 provides better lubricity and allows the bearing to conform to slight shaft misalignments. The higher tin content improves strength and wear resistance.

Mechanical Properties

C93200 has a tensile strength of 35,000 psi, yield strength of 18,000 psi, and hardness of 65 Brinell. C93700 is slightly stronger at 35,000 psi tensile but offers 18,000 psi yield and 60 Brinell hardness. The lower hardness of C93700 is actually an advantage in bearing applications — it allows the bearing surface to conform to the shaft and embed contaminant particles rather than scoring the shaft.

When to Use C93200 (SAE 660)

Choose C93200 for general-purpose bearings and bushings where loads are moderate and speeds are medium to high. It's the default choice for pump bushings, valve components, steam fittings, gears, and hydraulic cylinder parts. C93200 is also significantly easier to machine (70% machinability rating) and is available from virtually every bronze supplier in the country. If you're not sure which alloy you need, C93200 is almost always a safe starting point.

When to Use C93700 (SAE 64)

Choose C93700 when your application involves heavy loads at slow speeds — think crane wheels, rolling mill bearings, railroad components, and heavy machinery where shock loading is common. The higher lead content gives C93700 superior conformability, meaning it can accommodate slight shaft misalignments without galling. It also has better anti-seizure properties if lubrication is momentarily interrupted.

Cost and Availability

C93200 is the more economical option and the most widely stocked bearing bronze. Nearly every continuous cast bronze supplier carries it in a full range of solid bar, hollow bar, and finished bushing sizes. C93700 is readily available but may have slightly longer lead times in less common sizes. Both alloys are produced as continuous cast bronze, which provides the dense, uniform grain structure needed for reliable bearing performance.

Bottom Line

For most bearing and bushing applications, C93200 (SAE 660) is the right choice — it's proven, affordable, and universally available. Step up to C93700 when your application demands heavy-load, low-speed performance or when conformability and anti-seizure properties are critical. Either way, both alloys are available from Triton Bronze & Metals as continuous cast bar stock or finished parts, cut to length and shipped nationwide.