Bearings with different structures have different working characteristics, and different use occasions and installation positions have different requirements for the structure and characteristics of the bearings. The following factors should be considered in the selection of bearing types:
Spindle design: spindle speed, spindle rigidity, spindle temperature rise, spindle accuracy, spindle design life, and spindle reliability and stability. Because when designing the main shaft, when choosing which bearing to use, you should first determine the overall performance parameters of the main shaft, and roughly determine the performance requirements of the main shaft, for example: whether the main shaft requires a higher speed requirement or a higher rigidity requirement, in order to determine What type of spindle bearing to choose. Usually the most basic requirements for the spindle are as follows: 1. High rotation accuracy; 2. High speed; 3. Wide speed range; 4. High rigidity; 5. Low temperature rise; 6. High reliability. Some of the above requirements are in conflict with each other. Therefore, it is almost impossible for the main shaft to meet all the above requirements at the same time. Therefore, when designing the spindle support structure, the main performance of the machine tool should be considered. According to the different performance of the machine tool, different types of bearings and matching forms are selected as the supporting structure of the main shaft.
In terms of spindle structure: the choice of spindle bearings is ball bearings or cylindrical roller bearings; the pairing mode of spindle bearings is 2 groups, 3 groups, 4 groups or 5 groups. It may be a cylindrical roller bearing. The internal pairing method of the main shaft bearing generally adopts the pairing methods of front 2 and rear 1, front 2 and rear 2, and front 3 and rear 2; the lubrication method of the main shaft bearing generally adopts two lubrication methods: oil lubrication and grease lubrication. The design of the spindle requires the selection of an appropriate lubrication method.
In terms of the limit speed of the spindle bearing: select the corresponding dimensional accuracy of the spindle bearing according to the requirements of the spindle precision. Variety). Due to the different types of bearings, the speed also varies greatly. In general, bearings with low friction and low heat generation are suitable for high speeds. The design should strive for the rolling bearing to work under the condition of lower than its limit speed. See the detailed introduction of precision bearing limit speed.
The performance of the main shaft bearing: the fatigue life, rigidity, noise, heat and other factors of the main shaft bearing should be considered, and the most appropriate main shaft bearing clearance (preload) should be selected, because the bearing clearance and preload are directly related to the performance of the bearing The higher the speed, the more important it is, so it must be carefully considered. Improper selection will cause problems such as early failure of the spindle bearing or burning of the bearing channel; in addition, the choice of grease for the spindle bearing must also be cautious, and the spindle speed and temperature should be considered. 1. Working environment, select the spindle grease that meets its requirements, and the grease injection amount must also be injected according to the specified requirements. Generally, the grease injection amount is about 18%–25%, to ensure that the internal grooves, balls, and retainers of the spindle bearing Sufficient lubrication does not mean that the more grease is injected, the better. Excessive grease injection will cause problems such as excessive temperature rise of the spindle.
The installation of the main shaft bearing: the actual installation conditions, the accuracy of the shaft and the bearing seat, the tolerance fit, the pre-tightening force when fixing, the pre-tightening force and the clearance of the bearing after the actual installation should be considered, which are directly related to the installation of the main shaft bearing after use effect.

Technical information: The relationship between the contact angle of the spindle bearing and the speed and load: the larger the angle of the angular contact ball bearing, the greater the axial load carried and the lower the speed; the smaller the contact angle, the greater the axial load carried Smaller, the higher the speed, the greater the radial load; for example, for the same type of angular contact ball bearing, the rigidity of the C angle bearing is about 45% of the rigidity of the AC angle bearing, and the rigidity of the paired bearing mainly depends on the pairing of the spindle bearing In terms of preload and preload, it also depends on the rigidity of the shaft and housing. Preload: The relationship between spindle bearing preload and contact angle is similar, and it is one of the important factors related to the performance of spindle bearings. Generally, there are three types of preload for angular contact bearings: light preload A (L), medium preload B (M), and heavy preload C (H). Under different preload conditions, the greater the preload, the greater the radial rigidity and axial rigidity, the corresponding increase in the temperature rise of the spindle, the corresponding decrease in life and limit speed, and the excessive preload will cause bearing damage. Unfavorable problems such as loud noise and bearing channel burns occur.