Bearings and Lubricants
Bearings - Retainers or Cages
The function of a bearing retainer is to maintain proper distance
between rolling elements. Almost all roller bearings have stamped
retainers made of iron-silicon bronze or lead brass. Run-of-the-mill
bearings tend to have stamped steel retainers.
Stamped bronze or brass retainers for ball bearings are used more
in Europe than the U.S.; here, they are generally an extra-cost
option for high-speed applications. Plastic bearing retainers have
higher speed capability than metal retainers in most applications,
but these bearings are limited by temperature.
Retainer wear is inversely related to hardness so, in general,
the harder bearing retainer materials are more desirable, particularly
at high speeds. However, bearings using plastics such as phenolic
are often operating at temperatures up to 270°F, PTFE to 450°F,
and polyimide to 500°F. Common metals for low wear are S-Monel,
M-1, and 440C. Common softer metals include cobalt and copper alloys.
For most applications, bearing retainers can ride on the outer
or inner race. But for high speeds, they should ride on the outer
race and be thin enough to allow lubricant flow between retainer
and inner race. For high-speed small-bore bearings, it is often
necessary to use a silver-plated semihard tool-steel retainer with