Operating Conditions

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Lubricants serve a number of very important purposes in ball bearings, including:

  • protecting bearing surfaces from corrosion
  • reducing rolling and sliding friction
  • preventing metal-to-metal contact between balls and raceway
  • providing a barrier against external contaminants (grease)
  • removing heat (oil)

Lack of lubrication or inadequate lubrication is the most common cause of bearing failure.

Standard RBC Thin Section Ball Bearings are lubricated with either oil or grease. The unsealed bearings, the K series, are thoroughly coated in MIL-L-3150 oil and drained of excess. Sealed bearings are lubricated with MIL-G-23827 grease. The external surfaces of sealed bearings are lightly coated with the same grease for corrosion resistance. Additional lubricants are also available. Your RBC Sales Engineer can help select the appropriate lubricant for special applications.


Standard RBC Thin Section Ball Bearings can operate at temperatures from -65°F to 250°F. Temperatures up to 350°F can be reached if the bearings are temperature stabilized. By the use of special materials RBC can provide bearings for operation to 700°F. Contact your RBC Sales Engineer for recommendations on bearings operating above 250°F.

Limiting Speed

The limiting speed of a bearing is dependent upon a number of different factors including bearing size, bearing type, ball separator design, lubrication and loading. The limiting speeds for the bearings shown in this catalog are determined using the following:

Bearing Type
Load Condition
k Value
C or A
Radial or Thrust
Radial, Combined
Radial & Thrust,
or Moment

The k values shown give the maximum speeds at which a typical thin section ball bearing can operate. It is recommended that operating speeds of large diameter bearings in a given series be reduced up to 40% of the calculated rating to avoid high bearing temperatures. Speed ratings can also be impacted by load conditions, lubrication, alignment and ambient temperature. All of these factors must be considered when designing thin section ball bearings into your application.