The relationship between bearing and load direction:

Under normal circumstances, for pure radial load requirements, deep groove ball bearings or cylindrical roller bearings can be selected. And if it is a thrust ball bearing, then it is only suitable for bearing an appropriate amount of pure axial load. Moreover, one-way thrust ball bearings can only withstand bearing loads from one direction.

If it is a two-way thrust ball bearing, or a two-way thrust angular contact bearing, it can withstand axial loads in two directions. For example, if the bearing is subjected to combined radial and axial loads, then angular contact ball bearings or tapered roller bearings are usually used. And if it is a four-point contact ball bearing and a two-way thrust angular contact ball bearing, then it can withstand the combined load in both directions with the advantage of the bearing load.

However, if the bearing load in the combined load is relatively large, then the thrust bearing is only used to bear the axial load and has no relation to the radial load. If a suitable single-row radial ball bearing or a four-point contact ball bearing is used to bear the axial load, a proper radial clearance should be maintained between the outer ring and the seat hole.

If the load is off the center of the bearing, it may cause overturning moment. According to stainless steel bearing manufacturers, double row ball bearings can withstand overturning moments. However, it is recommended that you choose paired angular contact balls or paired tapered roller bearings. Face-to-face type, back-to-back type is better. Of course, cross tapered roller bearings can also be selected.

Relationship between bearing fit and load type

1. Basis for choosing cooperation

According to the load acting on the agent's bearing relative to the rotation of the ferrule, there are three types of loads borne by the ferrule: partial load, cyclic load, and swing load. Generally, cyclic load (rotating load) and swing load adopt tight fit; except for special requirements in use for local loads, tight fit is generally not suitable. When the bearing ring bears the dynamic load and heavy load, the inner and outer rings should adopt interference fit, but sometimes the outer ring may be a little looser, and it should be able to move axially in the housing hole of the bearing housing; When the bearing ring bears the swing load and the load is light, a slightly looser fit than a tight fit can be used.

2. The choice of fit: the base hole system is adopted for the bearing and the shaft, and the base shaft system is adopted for the fit with the housing. The matching of the bearing and the shaft is different from the tolerance matching system used in the machine manufacturing industry. The tolerance zone of the bearing inner diameter is mostly below the change. Therefore, under the same matching conditions, the matching of the bearing inner diameter and the shaft is closer than the usual matching . Although the tolerance zone of the bearing outer diameter and the tolerance zone of the base shaft system are below the zero line, their values ​​are different from the general tolerance system. When installing various types of bearings, select the tolerance zone of the shaft and housing hole. Tolerances of different tolerance grades of bearings, shafts and housings, or bearing samples.

Therefore, when choosing a fit, first consider the type of load bearing the ferrule. Generally, there are three types of load bearing rings:

1) Fixed load

The composite radial load acting on the ring is borne by the local area of ​​the ring raceway and transmitted to the opposite area of ​​the shaft or bearing seat. This load is called a fixed load. The characteristic of the fixed load is that the composite radial load vector is relatively static with the ferrule. Neither the ferrule nor the composite radial load rotates or rotates at the same speed are all fixed loads. The ferrule that bears the fixed load can choose a looser fit.

2) Rotating load

The synthetic radial load acting on the ferrule rotates along the circumferential direction of the raceway and is borne by various parts in sequence. This load is called a rotating load.

The characteristic of the rotating load is that the resultant radial load vector rotates relative to the ferrule. There are three conditions for rotating loads:

a. The load direction is fixed and the ferrule rotates;

b. The load vector rotates and the ferrule is stationary;

c. The load vector and the ferrule rotate at different speeds.

3) Swing load and variable load

Sometimes the direction and magnitude of the load cannot be determined with certainty. For example, in high-speed rotating machinery, in addition to the load of a fixed direction of the rotor weight, there is also a rotating load caused by an unbalanced mass. If this rotating load is greater than the fixed load If the rotating load is much smaller than the fixed load, the resultant load is still a swing load. Regardless of rotating load or swing load, its size and direction are constantly changing. In the variable working state, the load on some ferrules may sometimes be a rotating load, sometimes a fixed load, and sometimes a swing load. This load is called indefinite load.

Swing load and indefinite load should be treated the same as rotating load in the fit, too loose fit will cause damage to the mating surface.

For ferrules and shafts or seat holes that rotate relative to the load direction, transition fit or interference fit should be selected. The interference size is based on the principle that when the bearing is working under load, the ring does not produce "creeping" on the mating surface of the shaft or the seat hole. When the load is very light, or the ferrule occasionally rotates at a low speed under heavy load, a transition fit can be used. At this time, the shaft surface should have a higher hardness and a smaller surface roughness.

For heavy load occasions, the fit should usually be tighter than the light load and normal load occasions. The heavier the load, the greater the fit interference.