How to distinguish bearing accuracy?

Nov 05, 2022

In the purchase of bearings, sales staff will often ask customers a question: what class of accuracy do you need bearings? This is because different users have different needs for bearings, resulting in different manufacturers provide different bearing precision. But no matter how much more the bearing precision is required, there is still a grade standard for bearing precision. The following is an introduction to some of the precision classes of bearings.

The accuracy of bearings is generally divided into: dimensional accuracy and rotational accuracy.

Dimensional accuracy of bearings (items related to shaft and housing installation)

1、Allowable deviation of inner diameter, outer diameter, width and assembly width

2、The permissible deviation of the inner and outer compound diameters of the roller group

3、The permissible limit value of chamfering dimension

4. Permissible variation of width

Rotational accuracy of bearings (items related to runout of rotating bodies)

1. Permissible radial runout and axial runout of the inner ring and outer ring

2. Permissible lateral runout of the inner ring

3、The permissible variation of the tilt of the outer diameter surface

4、The permissible variation of the thickness of the thrust bearing raceway

5、The permissible deviation and permissible variation of the tapered hole

The standards for bearing accuracy are: Class 0, Class 6X, Class 6, Class 5, Class 4 and Class 2, making a total of six classes.
The accuracy of the bearings increases from Class 0. For general use Class 0 is sufficient, but for some conditions or occasions requiring high accuracy, Class 5 or higher is required.

The international standards for accuracy grades are based on ISO standards and are generally consistent with ISO standards, with individual cases being stricter than ISO standards. Divided into: 0 level, 6X Class, 6 Class, 5 Class, 4 Class, 2 Class, a total of six Classes.

The old Chinese bearing code standard is: G Class (0), E Class (6), D Class (5), C Class (4), B Class (2).
The current codes in China are based on the German DIN standard and are: P0 (0), P6 (6), P5 (5), P4 (4), P2 (2).

General standard Class P0, reaction in the bearing model is omitted not marked, only P6 or P6 Class above the bearing, grade code will appear in the bearing model.
For example: 6210 and 6210P5, which 6010 accuracy class for P0, just omitted not to write. This will easily give people the impression that P0 level is a non-precision class bearing.

Bearing applications and accuracy classes
Bearing accuracy rises from Class 0 onwards. For general applications Class 0 is sufficient, but for some applications requiring high precision conditions or occasions, Class 5 or higher is required.

Class 0: generally used for bearing systems with a rotational accuracy of more than 10 microns and is very commonly used. For example, the speed regulating mechanism on ordinary CNC lathes, tool walking mechanism, speed regulating mechanism of cars, speed regulating mechanism of big tractors, rotating mechanism of ordinary chemical machinery such as motors, centrifugal pumps and agricultural machinery.

Classes 6X~5: in the rotary precision in 5-10 microns or high speed precision bearing system, such as CNC lathe common bearings (front support point Class 5 , rear support point Class 6, finer instruments and equipment, instrument panel and its instrumentation, instrument panel and precision rotary mechanism.

Classes 4 ~ 2: in the ultra-instrument, such as fine coordinate milling machine, fine grinding machine drive gear system software, such as instrumentation, instrument panel and high-speed camera, etc., rotational accuracy of no more than 5 microns, the speed is relatively high.

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