Bi-material bearings consist of two materials, a metal shell and a plastic bearing surface. Common combinations include a steel-backed PTFE-coated bronze and aluminum-backed Frelon. Steel-backed PTFE-coated bronze bearings are rated for more load than most other bi-metal bearings and are used for rotary and oscillating motions. Aluminum-backed frelon are commonly used in corrosive environments because the Frelon is chemically inert

 

It is not at all unusual to come across a bronze sleeve bearing that has been performing satisfactorily for decades, even under severe operating conditions. In fact, a properly designed and maintained bronze bearing often outlasts the equipment it serves. Achieving such performance is not difficult, but it requires sound design, the right bearing material, accurate manufacture and, as with any mechanical equipment, diligent maintenance.

 

Bronzes are unquestionably the most versatile class of bearing materials, offering a broad range of properties from a wide selection of alloys and compositions. This data sheet describes the most used standard bearing bronzes and is aimed at helping the designer select the right bronze for the job at hand.

 

Good bearing design involves three fundamental elements: understanding the service environment, designing for proper lubrication and selecting the best bearing material for the job. Accurately assessing expected service conditions cannot be overemphasized; it is the basis for all subsequent decisions. Creating or at least identifying the lubrication mode in which the bearing will operate is equally important. Sometimes the mode can be established through design; other times it is simply dictated by operating conditions.

 

Finally, the bearing material selected must suit both the service environment and the operating mode. The wide array of properties offered by the bearing bronzes simplifies material selection process and helps insure that the alloy chosen will provide optimum bearing performance.

 

Satisfying the often conflicting demands of the particular mix of operating conditions expected makes almost every bearing design a compromise. Conditions involving extremes of load, speed or temperature in combination, whether low or high, are especially challenging. The bearing designer's task is to optimize that compromise to achieve the best possible performance in the finished product.

 

Having defined the bearing's operating conditions the next step is establishing the in-service lubrication mode - hydrodynamic, boundary or mixed film. Sometimes this can be done by design, other times it must be accepted by default.