Precision Bearings Review

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Precision bearings are a class of bearings which the bearings components are manufactured to extra tight tolerances for use at high speeds, radial and thrust loads. Typical end product applications which require precision bearings are dental work equipment, gas turbine main bearings, aircraft or aerospace installations.

Precision Bearings and Standards:

Precision bearings components are specified by ANSI/ABMA ABEC and RBEC Grades and Tolerances. These standards designate a manufacturing tolerance system for the bearings balls, inner and outer rings / races. The following :are the major tolerance specifications provided within ANSI/ABMA bearing standards.

  • Ball Grade – ball grade specifies dimensional and tolerance form, surface roughness and sorting tolerance for balls. For example, the level of spherically, expressed in millionths of an inch, e.g., a Grade 10 ball must have a roundness ( Circularity ) of each spherical element within 10 millionths of an inch.
  • Limits of Size Variation of Ball Diameter – defines the maximum and least material condition of the spherical diameters of a bearing ball.
  • Variation of Ball Lot Diameter – the difference between the mean diameters of the largest ball and smallest ball in a manufactured ball lot.
  • Deviation from Spherical Form – the difference between the largest and smallest diameters measurable on a single ball..
  • Surface Roughness (Ra) – Surface irregularities measured in micro-inches.
  • Inner and Outer Ring Bore Limits of Size - maximum and least material condition of the inner basic bore.
  • Inner Ring and Outer Ring Bore radial runout, axial runout, and width.

In general, precision bearings are produced to the more accurate ANSI/ABMA standards. The lower the ANSI/ABMA grade number the higher the accuracy requirements for each of bearings component used within the bearing assembly.