The assembly symbols of various NACHI precision angular contact ball bearing assembly methods are shown in Figure 4.1. The assembly sequence and load bearing direction of the assembled bearings are very important. Therefore, as shown in Figure 4.1, the outer diameter of the outer ring of the assembled bearing has '<' indicating the assembly symbol, so that the order of assembly can be confirmed. If the bearings can be assembled in the correct order, a '<' mark will be formed on the outer diameter of each bearing. DB DF DT FFB u200bu200bBFF FFF FFBB BBFF FFFB BFFF. The front side flatness (Af) and the back side flatness (Ab) of the free-form angular contact ball bearing are pre-adjusted to be the same, and the specified preload can be obtained regardless of the combination method (Fig. 4.2) NACHI free-form angular contact balls Bearings are supplied as a single product (group symbol: U) or in a combination of 2 (group symbol: DU). When two sets are provided, the mutual deviation of the inner diameter and outer diameter is controlled. When using a single product in combination, please select a bearing that is close to the actual measured size of the inner and outer diameters. The free assembly type of NACHI Ball Screw Support Bearing TAB series is marked with the assembly mark '<' on the outer diameter of the outer ring. Please refer to Figure 4.3 for the relationship between the grouping method and the grouping mark. The assembly method and the direction of the assembly mark of the freely configurable bearing (only for the TAB series of ball screw support bearings).