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. 19.2.

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)
  • 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
  • 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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