Bearing tolerance class

Bearings under the ABEC system are generally called precision bearings, with numbers from 1 to 9. The higher the number, the higher the accuracy level for bearing manufacturing（ Large = narrower tolerance zone range = more expensive price).

What does the tolerance zone mean?

Tolerance zone refers to a series of the differences between absolute and accurate measured dimensions used in production and processing. In short, the narrower the tolerance zone, the higher the machining accuracy.

Other grade numbering systems:

ABEC is only a method to define the tolerance class of bearings. The international organization for standardization and the German Standards Organization (DIN) have similar standards to measure the accuracy of bearings. In ISO and din systems, a smaller number means a narrower tolerance zone, and a larger number means a wider tolerance zone. This is contrary to the ABEC standard. Please see the corresponding table below.

ABEC ISO DIN
ABEC 1 Normal P0
ABEC 3 Class 6 P6
ABEC 5 Class 5 P5
ABEC 7 Class 4 P4
ABEC 9 Class 2 P2

abbreviation:

ABEC = ABMA system for rating ball bearing tolerances
ISO = International Standards Organization
DIN = German National Standards Organization

The bigger of the number, the better of quality.