In addition to the 2-row assembly, 3-row and 4-row angular contact ball bearings or ball screw support bearings for precision machine tool spindles are also commonly used. The assembled bearings here are manufactured as a pair of bearings, with a prescribed preload, and at the same time, strictly manage the mutual deviation of the outer diameter and the inner diameter of the assembled bearing. Therefore, it is necessary to avoid random assembly and use of a pair of assembled bearings. The main assembly method legend load capacity moment load rigidity and high speed characteristics. Back-to-back configuration (DB) ● Can bear radial load and axial load in two directions ● Due to the long distance between the load center and high moment load rigidity ● Assembly errors such as angular error can easily lead to increased internal load, early peeling and other damage. Face-to-face configuration (DF) u0026#1048675; ● Due to the short load center distance, the moment load rigidity is weak ● Because the moment load rigidity is weak, the increase of the internal load caused by the angle error can be suppressed. Therefore, it is suitable for use when the angle error cannot be avoided or the shaft is bent due to the load. Tandem configuration (DT) u0026#1048661; ● Can bear radial load and axial load in one direction ● Axial load capacity is twice that of single row bearings, so it is suitable for large axial loads in one direction. 3-row configuration (FFB) u0026#1048661; ● Can bear radial load and axial load in two directions ● The axial load capacity in one direction is twice that of single row bearings, but it is not equal to the preload distribution of each bearing , The single-row side is twice as much as the 2-row side. When rotating at high speed, it is difficult to set the preload reasonably due to the uneven distribution of the preload. 4-row configuration (FFBB) ● Can bear radial load and axial load in both directions ● Under the same preload clearance, the preload is increased by 2 times compared with the back-to-back configuration, and the rigidity is enhanced.