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