C93200, known throughout the bearing industry as "SAE 660 bronze," is a high-leaded tin bronze sand-cast specifically for plain bearing service. The composition runs roughly 81-85% copper, 6.3-7.5% tin, 6-8% lead, and 2-4% zinc — a deliberately high lead loading that puts C93200 firmly in the bearing-bronze category rather than the general-purpose casting category. This is one of the most widely used bearing bronzes in industrial machinery, hydraulic cylinders, pumps, and heavy equipment bushings anywhere in the world.

The tin provides the alloy's core strength and wear resistance, while the 6-8% lead does the heavy lifting for bearing performance: it forms a continuous network of soft inclusions that lubricate the running surface, resist galling against a steel shaft even under marginal lubrication, and embed abrasive contaminants rather than letting them score the shaft. This makes C93200 the default choice for bushings and thrust washers running at moderate to heavy loads and speeds, particularly in applications where oil-film lubrication can be interrupted — construction equipment, agricultural machinery, and general industrial drivetrains.

C93200's 6-8% lead content — among the highest of the common bearing bronzes — makes it one of the easiest cast bronzes to machine, for exactly the same reason it makes a good bearing. The lead exists as fine, soft globules dispersed through the copper-tin matrix rather than in solid solution. As the cutting edge advances, those globules shear well ahead of the tool, snapping the chip into short segments and depositing a thin lubricating film right at the tool-chip interface.

The result is low cutting forces, minimal heat buildup, and strong resistance to built-up edge formation, along with consistently good surface finish even on general-purpose tooling. Because the lead content is so high, chip control tends to be excellent across a wide range of feeds and speeds, and tool wear stays low since the material offers little abrasive resistance. As with any sand casting, expect some porosity in thicker sections and a harder oxidized skin on as-cast surfaces that calls for a slightly more durable edge on the first roughing pass.

Relative to the copper-alloy machinability benchmark set by C36000 free-cutting brass at 100%, high-leaded bronzes like C93200 can match or exceed that figure in many operations, since their lead content by weight often runs even higher than free-cutting brass. It's a genuinely easy alloy to cut, which is part of why it remains a workhorse bearing material despite being more expensive per pound than plain steel bushings.