Precision bearings are classified into P0, P6, P5, P4, P2 according to ISO grading standards. The grades increase in order, with P0 being of ordinary precision and the other grades being of precision grade. Of course, different grading standards and types of bearings have different grading methods, but the meaning is the same. Precision bearings require the rotating body to have high runout accuracy, high-speed rotation, and minimal friction and friction variation in terms of performance. Due to the precision of precision bearings being within 1 μ m, high dimensional and shape accuracy is required for their matching components (shaft, bearing seat, end cap, retaining ring, etc.), especially the precision of the mating surface should be controlled within the same level as the bearing. This is crucial and often overlooked. It must also be noted that if the matching parts of precision bearings do not meet the above requirements, the precision bearings often experience errors several times or even more than 10 times larger than the original bearings after installation, and cannot be considered precision bearings at all. The reason is that the errors of matching parts are often not simply added to the errors of the bearings, but amplified by different factors and added
