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        According to the ISO classification standard, precision bearings are divided into: P0, P6, P5, P4, P2. The grades are increased in turn, in which P0 is the general accuracy, and other grades are precision grades. Of course, different classification standards, different types of bearings, their classification method is different, but the significance is one to. The performance of precision bearing requires high runout accuracy, high-speed rotation and small friction and friction change.

Precision bearing and ordinary bearing should be distinguished from the following points:

1. The size deviation (inner diameter, outer diameter, ellipse, etc.) of products with high accuracy level is smaller than that of products with low accuracy level;

2. The required values of rotation accuracy are different. For products with high accuracy level, their rotation accuracy (inner diameter runout, outer diameter runout, end surface raceway runout, etc.) are stricter than those of products with low accuracy level;

3. The required values of surface shape and surface quality are different. The surface shape and surface quality (surface roughness of raceway or raceway, circular deviation, groove shape deviation, etc.) of products with high precision grade are stricter than those of products with low precision grade;

4. The material properties of the products with high precision grade are more favorable than those with general accuracy grade.