The purpose and principle of bearing preloading

Due to the clearance of the bearing, under load conditions, the inner and outer rings in operation will produce relative movement, which will reduce the stiffness of the bearing, cause radial and axial vibration of the shaft, and affect the working accuracy and life of the machine. In order to reduce this vibration, preload bearings are usually installed on high-precision and high-speed mechanical equipment, that is, a certain load (radial or axial) is applied to the bearing in advance during installation to eliminate its original clearance.，thus the bearing body and the inner and outer rings are elastically deformed, to prevent from relative displacement between the inner and outer rings when the bearing is working.

1. The purpose of preload

The preload spindle bearing can eliminate the original clearance of the ball and raceway and form a certain elastic deformation.so the bearing has a certain rigidity under an external load, the installed bearing is opposite to the direction of the external load, which will not cause a gap between the ball and the raceway due to the external load, so as to improve the rotation accuracy of the spindle, strengthen the rigidity of the spindle and increase the service life, while reduce noise.

2. The principle of preload

The size of the preload is generally determined according to the size of the working load, the rotation accuracy and speed of the spindle.

1）In applications where the spindle load is small, the rotation accuracy is high, and the speed is low, the larger preload can be selected.

2）In applications where large working load and high speed, a smaller preload should be selected because it is easy to cause heat and expand.