Bearing accuracy

The accuracy of the bearing includes dimensional accuracy and rotation accuracy.

Dimensional accuracy is an item required when the bearing is installed on the shaft or bearing box. It includes the inner diameter, outer diameter, width, chamfering dimensional tolerance or allowable value. The geometric accuracy includes the allowable value of the inner diameter deviation, the average inner diameter difference, the outer diameter deviation, the average outer diameter difference, and the parallel difference of the end face of the ferrule. Rotation accuracy is specified for oscillation during rotation, including radial oscillation and axial oscillation of the inner ring and outer ring, as well as the tolerance range of the inner ring side swing and outer diameter surface perpendicularity.

Dimensional accuracy (items related to shaft and housing installation)

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

2. The allowable deviation of the inner and outer round diameters of the roller group

3. Allowable limit value of chamfer size

4. Allowable variation of width

Rotation accuracy (items related to the beating of rotating element)

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

2. Allowable lateral runout of the inner ring

3. Allowable variation of the inclination of the outer diameter surface

4. Allowable variation in thickness of thrust bearing raceway

5. Allowable deviation and allowable variation of tapered hole

Classification of bearing accuracy grades

The accuracy grades of the bearings range from ordinary grade 0 to grade 6, grade 5, grade 4 and grade 2, improving in turn.

1. The tolerance level of the bearing is mainly determined according to the rotation accuracy requirements of the shaft pair support.

Class 0 bearings are ordinary bearings and are the most widely used in various machines. Used in a very wide range of general bearing systems with a rotation accuracy greater than 10um. This type of bearing is mostly used in general machines that do not require high rotation accuracy, such as the speed change mechanism of ordinary machine tools, feed mechanism, automobile, tractor speed change mechanism, ordinary motors, water pumps and agricultural machinery and other general machinery rotating mechanisms.

6 (6x) bearings are high-grade bearings, and grade 5 bearings are precision bearings. In precision bearing systems with a rotation accuracy of 5-10um or higher speeds, such as bearings used in ordinary lathes (front support uses 5 grades, and rear supports 6 Level) more precise instruments, meters, and precision instruments, meters, and precision rotating mechanisms.

4. Class 2 bearings are called ultra-precision bearings. In ultra-precision instruments with a rotation accuracy of less than 5um or a high speed, such as precision coordinate boring machines, gear systems of precision grinders, precision instruments, meters, and high-speed cameras.

2. Accuracy grade code of previous old codes for bearings in various countries

The standards formulated by various countries are based on ISO standards, which are generally consistent with ISO, and some are stricter than ISO standards.

The old code standards used to be G-level (level 0), E-level (level 6), D-level (level 5), C-level (level 4), and B-level (level 2).The current code generally adopts the German DIN standard.

P0 (level 0), P6 (level 6), P5 (level 5), P4 (level 4), P2 (level 2).

Generally, the standard grade P0 is reflected in the bearing model, and the name is omitted. Only the bearings of P6 or above can appear in the bearing model identification.

For example: 6205 and 6205/P5, where the accuracy level of 6205 is P0, but the mark is omitted. This gives people the impression that P0 grade is a non-precision grade bearing.

In addition to the difference in processing technology, the bearing accuracy grade is also reflected in the difference in price.

For example: the price of domestic bearings, price of P6 precision bearings are 1.5 times that of P0, P5 precision bearings are 2 times that of P0, and P4 precision is 2.5 times that of P5.