First, the purpose of matching The purpose of matching is to firmly fix the inner ring or outer ring of the bearing with the shaft or housing, so as to avoid unfavorable axial sliding on the mutual mating surface. This unfavorable axial sliding (called creep) can cause problems such as abnormal heat generation, wear of the mating surfaces (and thus intrusion of worn iron powder into the bearing interior), and vibration, making the bearing unable to function fully. Therefore, for bearings, due to the rotation under load, it is generally necessary to make the ring with interference so that it can be firmly fixed with the shaft or housing.

Second, the dimensional tolerances of shafts and housings The dimensional tolerances of shafts and housing holes of the metric series have been standardized by GB/T275-93 'Cooperation of Rolling Bearings with Shafts and HousingsDetermine the fit of the bearing to the shaft or housing. The selection of the cooperation The selection of the cooperation is generally carried out according to the following principles. According to the direction and nature of the load acting on the bearing and which side of the inner and outer rings rotates, the load on each ring can be divided into rotating load, static load or non-directional load. The ferrule that bears the rotating load and the non-directional load should be a static fit (interference fit), and the ferrule that bears the static load can be a transition fit or a dynamic fit (clearance fit). When the bearing load is large or subjected to vibration and shock load, its interference must be increased. When using hollow shaft, thin-walled bearing housing or light alloy, plastic bearing housing, it is also necessary to increase the amount of interference. When it is required to maintain high rotation, high-precision bearings must be used, and the dimensional accuracy of the shaft and bearing housing should be improved to avoid excessive interference. If the interference is too large, the geometrical accuracy of the shaft or bearing housing may affect the geometrical shape of the bearing ring, thereby compromising the rotational accuracy of the bearing. Non-separable bearings (such as deep groove ball bearings) use static fit on the inner and outer rings, so it is extremely inconvenient to install and disassemble the bearing. It is best to use dynamic fit on one of the inner and outer rings.