Bearing designations

Metric bearings

The designations of metric tapered roller bearings follow one of the following principles:
  • The series designations in accordance with ISO 355 consist of a digit and two letters. The digit represents the contact angle. The two letters represent the diameter and width series, respectively. This is followed by a three-digit bore diameter d [mm]. The basic designations of SKF tapered roller bearings start with the letter T, e.g. T2ED 045.
  • Designations established prior to 1977 are based on the system shown under Basic designations, e.g. 32206 (table 1).
  • Metric bearings with the designation prefix J follow the ABMA designation system, which is used for inch bearings (→ ANSI/ABMA Std. 19.1).

Inch bearings

Inch tapered roller bearing designations are in accordance with ANSI/ABMA Std. 19.1.

Within a series:

  • roller and cage assemblies are equal but the inner and outer rings can have different sizes and designs
  • any inner ring with roller and cage assembly (cone) can be assembled with any outer ring (cup)


  • Cup and cone have individual designations and can be supplied separately (fig. 1).
  • The designations of cups and cones, as well as the series, consist of a three- to six-digit number, which may be prefixed to characterize a bearing series from extra-light to extra-heavy.
  • The complete bearing designation is an abbreviated combination of cone and cup designations. It consists of the cone designation followed by the complete or parts of the cup designation, separated by an oblique stroke (table 2).
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