As the basic accessory of the machine tool, the performance of the spindle bearing directly affects the speed, rotation accuracy, rigidity, noise, temperature rise and thermal deformation of the machine tool, and then affects the accuracy and surface quality of the machined parts. Therefore, high-performance machine tools must be equipped with high-performance bearings.

The accuracy of rolling bearings is generally divided into five levels: P0, P6, P5, P4 and P2. The accuracy of bearings used in precision machine tool spindles should be P5 and above. For the spindle bearing for high-speed and high-precision machine tools such as CNC machine tools and machining centers, ultra-precision bearings of P4 and above are required.

With the development of CNC machine tool spindles to high speed, high-speed machining can effectively improve the machining efficiency of the machine tool and shorten the machining cycle of the workpiece. This requires the machine tool spindle and its related parts to adapt to the needs of high-speed machining. Ceramic material Si3N4 has excellent properties such as low density, high elastic modulus, low thermal expansion coefficient, wear resistance, high temperature resistance, and corrosion resistance, making it an ideal material for manufacturing high-speed precision bearings. In view of the difficult processing of ceramic materials, precision ceramic bearings are mostly hybrid ceramic ball bearings in which the rotating body is ceramic and the inner and outer rings are still made of chrome steel.

As a precise, efficient and sensitive transmission element, ball screw pair should use high-precision screws, nuts and balls, but also bearings with high axial rigidity, small friction torque and high running accuracy. At present, the most widely used single-row thrust angular contact ball bearing is used for ball screw support.

Under normal circumstances, the precision machine tool bearings we mentioned refer to spindle bearings and screw bearings with accuracy of P5 and above.