Five kinds of rolling bearings commonly used in machine tool industry

There are five kinds of rolling bearings commonly used in machine tool industry
1. Deep groove ball bearing
This kind of bearing is generally only used to bear radial load, because the clearance is not adjustable, so it is often used in the situation of low precision and no pre tightening, such as ordinary drilling machine spindle.
2. Angular contact ball bearing
This kind of bearing can bear radial and axial loads at the same time. Because it will cause internal axial force when bearing radial load, it should be installed and used. Its configuration methods include "back-to-back", "face-to-face", "series connection" and "multi connection", and the stiffness of main shaft can be improved by preloading. The contact angles of these bearings are 15 °, 25 ° and 40 ° respectively. The b7000cy high-precision angular contact ball bearing with 15 ° contact angle is a special bearing specially designed for high-speed grinder spindle. In addition to the change of internal structure design, the rings and rolling elements are made of high-quality electroslag bearing steel. The cage material is phenolic laminated pipe, and the tolerance level is 5, 4 and 2. Therefore, this kind of bearing has high rotation accuracy and limit speed, small friction and low temperature rise.
3. Two way thrust angular contact ball bearing
The 230000 two-way thrust angular contact ball bearing is usually selected. The contact angle is 60 ° and it is composed of a seat ring with lubricating oil hole, two shaft rings, a spacer ring and two groups of steel balls and cage components. Choosing the appropriate height of spacer can make the bearing have the required preload after assembly.
This kind of bearing can bear two-way axial load, has good rigidity, low temperature rise, high speed under normal lubrication, and is easy to assemble and disassemble. As a new structure, it is widely used in grinding machine, lathe, boring machine, milling machine, drilling machine and other spindles, and is often combined with double row cylindrical roller bearing in use.
4. Double row cylindrical roller bearing
This kind of bearing can bear larger radial load and allow higher speed. The two rows of rollers in the bearing are arranged in a cross way, and the fluctuation frequency is twice as high as that of the single row bearing, and the amplitude is reduced by 70%. There are two kinds of bearings in common use: NN30 / W33 and nn30k / W33. The inner ring of the bearings has rib and the outer ring can be separated; The outer rings of nnu49 / W33 and nnu49k / W33 series bearings are provided with rib and the inner rings are separable. The inner rings of nn30k / W33 and nnu49k / W33 series bearings are tapered holes (taper 1:12), which are matched with the tapered Journal of the main shaft. By moving the inner rings axially, the inner rings can be expanded to reduce the bearing clearance and even preload the bearing. The cylindrical hole bearing usually adopts hot fitting, and uses interference fit to reduce the bearing clearance or achieve the purpose of preloading. For nnu49 series bearings with separable inner ring, the finish machining of raceway is usually carried out after the inner ring is installed with the spindle to obtain high spindle rotation accuracy.
5. Tapered roller bearing
It can bear both radial and axial load, and double row tapered roller bearing can bear bidirectional axial load. Because of the sliding friction between the big end of tapered roller and the inner ring rib, the limit speed of tapered roller is often lower than that of cylindrical roller bearing of the same size. Hollow tapered roller bearings can be cooled by oil to reduce the temperature rise and increase the allowable speed. But the manufacturing process of this kind of bearing is complex, and the requirement for the lubrication system of machine tool is also high. Generally, it is only used on the horizontal spindle with special requirements.