Can cylindrical roller bearing only bear radial load?

Cylindrical roller bearings are generally only used to bear radial load, only when the inner and outer rings of single row bearings with ribs can bear smaller directional axial load or larger clearance axial load.

Relationship between bearing and load direction:

Under normal circumstances, for the use of pure radial load requirements, can choose deep groove ball bearing or cylindrical roller bearing. If it is a thrust ball bearing, then it is only suitable for bearing an appropriate amount of pure axial load. And the one-way thrust ball bearing can only bear the bearing load from one direction.

If it is a two-way thrust ball bearing, or a two-way thrust angular contact bearing, then it can bear two directions of axial load. For example, if the bearing bears the combined load of radial and axial, then the angular contact ball bearing or tapered roller bearing is usually used. 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 of two directions with the advantage of bearing fou load.

However, if the combined load of the bearing fou load is relatively large, then the thrust bearing is only used to bear the axial load, and has no correlation with 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 deviates from the center of the bearing, it may cause overturning moment. Stainless steel bearing manufacturers, and double row ball bearings can withstand overturning torque, but it is recommended that you choose a pair of angular contact ball, or pair tapered roller bearings, face-to-face type, back-to-back type is better. Of course, you can also choose cross tapered roller bearings.

Relationship between bearing fit and load type

1. Basis of selection and coordination

According to the rotation of the load acting on the bearing relative to the ring, the ring bears three kinds of load: local load, cyclic load and swing load. In general, tight fit is used for cyclic load (rotating load) and swing load; in addition to special requirements for local load, tight fit is generally not suitable. When the bearing ring is under the sustained load and heavy load, the inner and outer rings should adopt interference fit, but sometimes the outer ring can be a little loose, and it should be able to move axially in the bearing housing hole; when the bearing ring is under the swing load and the load is light, it can adopt the fit slightly loose than the tight fit.

2. Selection of fit: the fit between bearing and shaft adopts base hole system, while the fit between bearing and shell adopts base shaft system. The matching of bearing and shaft is different from the tolerance matching system used in machine manufacturing industry. The tolerance zone of bearing inner diameter is mostly below the change. Therefore, under the same matching condition, the matching ratio of bearing inner diameter and shaft is usually close. Although the tolerance zone of bearing outer diameter is below the zero line with that of basic shaft, its value is different from that of general tolerance system. Selection of tolerance zone for shaft and shell hole during installation of various bearings. Tolerance of different tolerance grades of bearings to fit shaft and housing, or bearing samples.

Therefore, in the selection of fit, the first thing to consider is the type of load on the ring. Generally, there are three types of rings bearing loads as follows:

1) Fixed load

The synthetic radial load acting on the ring is borne by the local area of the ring raceway and transmitted to the relative area of the shaft or bearing seat. This kind of load is called fixed load. The characteristic of the fixed load is that the synthetic radial load vector and the ring are relatively static. Both the ring and the resultant radial load do not rotate or rotate at the same speed. Loose fit can be selected for the ferrule bearing fixed load.

2) Rotating load

The synthetic radial load acting on the ring rotates along the circumferential direction of the raceway, which is successively borne by various parts. This kind of load is called rotating load.

The characteristic of rotating load is that the resultant radial load vector rotates relative to the ring. There are three cases of rotating load

a. The load direction is fixed and the ring 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 indefinite load

Sometimes, the direction and magnitude of the load can not be determined accurately. For example, in high-speed rotating machinery, in addition to the load with fixed rotor weight, there is also the rotating load caused by unbalanced mass. If the rotating load is much larger than the fixed load, the combined load is still the rotating load; If the rotating load is much smaller than the fixed load, the combined load is the swing load. No matter rotating load or swinging load, its size and direction are constantly changing. In variable working condition, the load on some rings may be rotating load, fixed load or swinging load. This kind of load is called indefinite load.

The swing load and the indefinite load should be treated as the same as the rotating load in the matching. The loose matching will cause the damage of the matching surface.

Transition fit or interference fit should be selected for the ring and shaft or seat hole rotating relative to the load direction. The interference size is based on the principle that when the bearing works under load, the ring will not produce "creep" phenomenon on the matching surface of the shaft or seat hole. When the load is very light or the ring occasionally rotates at low speed under heavy load, the transition fit can be selected. At this time, the shaft surface should have higher hardness and smaller surface roughness.

For heavy load cases, it is usually tighter than that for light load and normal load cases. The heavier the load, the greater the interference.