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Rotary Bearing Tolerances

Many countries throughout the world have their own standards organizations. For example, Germany, Japan, Korea, Russia, and China are major bearing producers and all have industrial standards that cover ball and roller bearings. In almost all cases, these standards are similar to or state equivalency with ISO 492. The Table below shows the equivalent tolerance grades for three of the most common standards.

Bearing Classes by Standard
ANSI Standard 20 ISO 492 DIN 620
ABEC 1 Class Normal P0
ABEC 3 Class 6 P6
ABEC 5 Class 5 P5
ABEC 7 Class 4 P4
ABEC 9 Class 2 P2

In the table above are links to the ABEC tables listing tolerances for both inner and outer rings, in both inch and metric units. These tables are useful in determining sizes and tolerance for components, such as shafts and housings. The designer should always do a tolerance stack up study at both maximum and least material conditions when sizing components, particularly when designing for miniature ball bearings. Some tolerances have been omitted for clarity.

Since radial runout is sometimes misunderstood, we offer and explanation with sketches below to clarify the standard technique by which it is measured.


Radial Runout Tolerance Measurement Techniques

The proper technique to measure the radial runout is to hold (i.e., fix) either the inner or outer ring and rotate the ring under consideration.  Typically the ring is rotated one revolution while an indicator or gauge records the variation during the movement as shown below.

                  
Inner Ring Runout Measurement Arrangement

Operator reads the indicator while rotating inner ring one revolution with dead weight placed on inner ring.
  Outer Ring Runout Measurement Arrangement

Operator reads the indicator while rotating outer ring one revolution with dead weight placed on outer ring.











The Precision Alliance | More than components... Solutions! The Precision Alliance | More than components... Solutions!