Why Use Bronze for Bearings?

Metallic bearings are often made from bronze.

Bearings are mechanical devices that allow two parts to rotate with respect to each other. The wheel bearings on your car, for example, allow the axle and wheel to turn while remaining connected to the body of your car. Nowadays bearings are made from a wide variety of materials, including both metals and polymers. Bronze is a popular bearing metal that offers a variety of advantages.

Durability

The choice of bearing material is very important in determining how long the product will last and what kind of performance it delivers. Bronze bearings can be very durable. According to the Copper Development Association, if they are properly designed and maintained, bronze bearings can outlast the machinery itself. It also features a much lower coefficient of friction than steel-on-steel, meaning the amount of friction is less; this property reduces the amount of scoring on steel shafts and improves performance.

Corrosion

Bronze exhibits relatively good corrosion resistance. While not as corrosion-resistant as silver or stainless steel, bronze is superior to tin, lead, cast iron and steel. When it remains exposed to the air over a long period of time, the surface of a bronze component forms a copper oxide layer that protects the metal beneath from further corrosion. The presence of sulfur or chlorine compounds, however, accelerates bronze corrosion and deterioration markedly.

Alloys

One of the features that makes bronze so versatile as a bearing material is the wide range of bronze alloys you can buy. Each of these alloys has different properties and is thus suited to certain applications. Tin bronzes, for example, feature improved strength and hardness combined with good ductility; aluminum bronzes are even stronger and have superior corrosion resistance. Although high leaded tin-bronzes are weaker, they have excellent antifriction properties and can be machined easily. Moreover, the high-lead products embed dirt as tiny microscopic particles, reducing scratching or scoring of the steel shaft and thus extending effective lifespan.

Considerations

Another option is sintered bronze, a type of porous bronze bearing that can absorb oil and thereby provide for improved lubrication. Like aluminum bronze, manganese bronze combines high strength with good corrosion resistance. Bronze bearings are much better conductors of heat than nonmetallic materials, which is especially helpful in cases where high speeds cause heat to accumulate quickly. No bearing material is perfect, because each situation calls for certain properties, but bronze's desirable characteristics and the menu of different alloys you have available makes bronze an attractive choice for many applications.

References

• Copper Development Association: Selecting Bronze Bearing Materials
• Bearings Reference Center: Bearings 101
• US General Services Administration: Bronze, Characteristics, Uses and Problems