Six issues of bearing clearance

The so-called bearing clearance refers to the amount of movement when the bearing is not installed on the shaft or bearing box, one side of the inner or outer ring is fixed, and then the other side is not fixed to move radially or axially. According to the moving direction, it can be divided into radial clearance and axial clearance. Clearance for the use of bearings is also very important, bearing manufacturers tell you must not ignore this point.

There are six major issues of bearing clearance

1. The size of the running clearance (called working clearance) has an impact on the rolling fatigue life, temperature rise, noise, vibration and other properties of the bearing.

2. When measuring the clearance of the bearing, in order to get a stable measurement value, the specified measurement load is usually applied to the bearing. Therefore, the measured value is larger than the real clearance (called theoretical clearance), which increases the elastic deformation caused by the measured load. For roller bearings, the elastic deformation is small and can be ignored.

3. The internal clearance of the bearing before installation is generally represented by the theoretical clearance.

4. From the theoretical clearance minus the bearing installed in the shaft or shell due to interference fit after the expansion or contraction of the ring clearance is called "installation clearance". The clearance after adding or subtracting the dimension variation caused by the temperature difference inside the bearing is called "effective clearance".

5. The bearing is installed with the clearance when the bearing is placed under a certain load, that is, the effective clearance plus the elastic deformation caused by the bearing load, so as to be called the "working clearance".

6. When the working clearance is slightly negative, the fatigue life of the bearing is the longest, but with the increase of the negative clearance, the fatigue life decreases significantly. Therefore, when selecting the bearing clearance, it is generally appropriate to make the working clearance zero or slightly positive. In addition, when the rigidity of the bearing needs to be improved or the noise needs to be reduced, the working clearance should be further taken as a negative value, while when the temperature of the bearing rises sharply, the working clearance should be further taken as a positive value, and so on.