How to choose rolling bearings?

According to the rotation of the load acting on the bearing relative to the ferrule, there are three kinds of loads on the rolling bearing ring: partial load, cyclic load, and swing load. Generally, the cyclic load (rotary load) and the oscillating load are tightly fitted; in addition to the special requirements of the local load, it is generally not suitable to use a tight fit. When the rolling bearing ring is subjected to the holding load and is heavy, the inner and outer rings should be equipped with interference fit, but sometimes the outer ring can be loosened a little and should be able to swim axially in the housing hole of the bearing housing; When the bearing ring is subjected to the oscillating load and the load is light, a looser fit than the tight fit can be used.

Load size
The amount of interference between the bearing ring and the shaft or housing bore depends on the size of the load. When the load is heavy, a large interference fit is used. When the load is light, a small interference fit is used. Generally, when the radial load P is less than 0.07C, it is a light load, P is greater than 0.07C and equal to or less than 0. When 15C is normal load, P is greater than 0. When 15C is heavy load (C is the rated dynamic load of the bearing).

Operating temperature
When the bearing is running, the temperature of the ferrule is often higher than the temperature of the adjacent parts. Therefore, the inner ring of the bearing may loosen with the shaft due to thermal expansion, and the outer ring may affect the axial movement of the bearing in the housing hole due to thermal expansion. When choosing to cooperate, the temperature difference and expansion and contraction of the bearing device part should be taken into consideration. When the temperature difference is large, the interference between the selected shaft and the inner ring should be larger.

Rotation accuracy
When the bearing has high rotation accuracy requirements, in order to eliminate the effects of elastic deformation and vibration, the clearance fit should be avoided.

Structure and material of bearing housing hole
For the form housing hole, it is not advisable to use an interference fit when mating with the bearing outer ring, nor should the outer ring rotate in the housing hole. For bearings mounted on thin-walled housing bores, light metal housing bores or hollow shafts, a tighter fit than thick-walled housing bores, cast iron housing bores or solid shafts should be used.

Easy to install and disassemble
For heavy machinery, the bearings should be loose. When a tight fit is required, separate bearings, tapered bores and adapter sleeves or withdrawal sleeve bearings are available.

Axial displacement of the bearing
In the cooperation, when a ferrule of the bearing is required to be axially movable during operation, the outer ring of the bearing and the hole of the bearing housing should be loosely fitted.

Matching choice
The bearing and the shaft are matched by a base hole, and the coupling with the outer casing is made of a base shaft. The cooperation between the bearing and the shaft is different from the tolerance matching system used in the machine manufacturing industry. The tolerance of the inner diameter of the bearing is mostly less than zero. Therefore, under the condition of the same fit, the matching ratio of the inner diameter of the bearing to the shaft is generally tight. . Although the tolerance zone of the bearing outer diameter and the tolerance zone of the base shaft are below the zero line, the value is not the same as the general tolerance system.