Installation of angular contact ball bearings

Angular contact ball bearings are more complex to install than deep groove ball bearings, mostly in pairs and require preloading. The installation is good, the working accuracy and bearing life of the main machine can be greatly improved; otherwise, the accuracy will not be met, and the service life will be affected.
Installation form

Angular contact ball bearings are available in back-to-back, face-to-face, and series arrangements. When installed back to back (the wide end faces of the two bearings are opposite), the contact angle of the bearing spreads along the direction of the rotation axis, which increases the radial and axial support angle rigidity and the maximum deformation resistance; face to face (the narrow end faces of the two bearings are opposite) When installed, the contact angle of the bearing converges toward the direction of the rotation axis, and the ground bearing angle is less rigid. Since the inner ring of the bearing protrudes from the outer ring, when the outer rings of the two bearings are pressed together, the original gap of the outer ring is eliminated, and the preload of the bearing can be increased; when the series arrangement (the wide end faces of the two bearings are in one direction) is installed The contact angles of the bearings are the same and parallel, so that the two bearings share the working load in the same direction. However, in order to ensure the axial stability of the installation when using this type of mounting, two pairs of bearings arranged in series must be mounted opposite each other at both ends of the shaft.

Preloading
Preloading can be done by grinding the end face of a ferrule in the bearing, or by placing two spacers of different thickness between the inner and outer rings of a pair of bearings, clamping the bearings together to make the steel ball and the raceway Get it in close contact.

The preloading has a great influence on the service life of the bearing. According to the relevant information, when the bearing is equipped with 0.012mm interference, the service life is reduced by 38%. When there is 0.0116mm interference, the service life is reduced by 50%; When the bearing is assembled with a gap of 0.004 mm, the service life is significantly reduced. When there is a gap of 0.008 mm, the service life is reduced by 70%. Therefore, it is important to make a reasonable choice of the size of the preload. Generally, a small preload should be used for high speed, and a large preload should be used for low speed. At the same time, the preload should be slightly greater than or equal to the axial working load.

Preload calculation
When the preload is selected, the minimum preload is calculated as follows:
Aomin=1.58tgaR±0.5A(N)
Radial load acting on the bearing (N)
Axial load acting on the bearing (N)
The angle between the straight line passing through the contact point of the steel ball and the raceway and the straight line passing through the center plane of each steel ball (ie, the nominal contact angle):
7000C a=15°
7000AC a=25°
7000B a=40°

Each bearing in a pair of bearings is calculated according to this formula. The "+" in the formula is used for the bearing whose axial working load reduces the original pre-common value; "the bearing used for the axial working load to increase the original pre-common value. Two pairs The minimum preload of the bearing is the maximum of the two values obtained by the two bearings (according to the assembly experience, a preload of about 50N is generally taken).
Preload adjustment
Dry running test. After the angular contact ball bearing has passed the assembly inspection, the test shall be carried out at the working speed for no less than 2 hours, and the temperature rise shall not exceed 15 °C.