In bearing installation, engineers are most concerned about how to operate correctly. If the operation is improper, it is likely to cause damage to the bearing. If it is operated at high speed and the working temperature is high, special attention should be paid to the fit of the rotating ferrule not to be too loose to prevent eccentric vibration, and there must be no gap in the fit of the fixed ferrule to prevent the ferrule from deforming under load. Excite vibration. The burning interference of the rotating ferrule should also be smaller within the possible range. As long as the effect of thermal expansion at the working temperature and the effect of centrifugal force at the maximum speed are ensured, it will not cause creep or slippage of the tight-fitting surface. According to the size of the working load and the size of the bearing, the fixed ring selects a very small clearance fit or an interference fit. Too loose or too tight is not conducive to maintaining the original precise shape. It is necessary to accurately calculate the interference amount of the rotating ferrule as well as the appropriate amount of the fixed ferrule. The roundness of the shaft and the seat hole and the verticality of the shoulder should be required in accordance with the corresponding accuracy of the bearing. The assembly accuracy of the cage is guaranteed by the special assembly mould, which can fully guarantee the assembly accuracy requirements of the bearing. The condition of adopting small interference fit for the fixed ring is that both sides of the matching surface have high shape accuracy and small roughness, otherwise it will be difficult to install and disassemble. In addition, the effect of thermal elongation of the spindle needs to be considered.　 Swing load and indeterminate load should be treated the same as rotating load in the fit, too loose fit will cause damage to the mating surface. For ferrules and shafts or seat holes that rotate relative to the load direction, transition fit or interference fit should be selected. The interference size is based on the principle that when the bearing is working under load, the ring does not produce 'creeping' on the mating surface of the shaft or the seat hole. When the load is very light, or the ferrule occasionally rotates at a low speed under heavy load, a transition fit can be used. At this time, the shaft surface should have a higher hardness and a smaller surface roughness. For heavy load occasions, it should usually be tighter than the fit in light load and normal load occasions. The heavier the load, the greater the fit interference should be. The main shaft using paired double angular contact ball bearings usually has a lighter load. If the fit interference is too large, the internal axial preload will be significantly too large, which will cause adverse effects. The main shaft of the double-row short cylindrical roller bearing and the main shaft of the tapered roller bearing have a relatively large load, so the fit interference is relatively large. Sometimes the direction and magnitude of the load cannot be determined with certainty. For example, in high-speed rotating machinery, in addition to the load of the fixed direction of the rotor weight, there is also the rotating load caused by the unbalanced mass. If this kind of rotating load is greater than the fixed load If the rotating load is much smaller than the fixed load, the resultant load is still a rotating load. Regardless of rotating load or swing load, the size and direction of the bearing are constantly changing. In the variable working state, the load on some ferrules may sometimes be a rotating load, sometimes a fixed load, and sometimes a swing load. This load is called indefinite load.