During the installation process of bearings, the preload should be controlled mainly for angular contact ball bearings, eccentric bearings, tapered roller bearings, double-row cylindrical rollers with tapered holes, etc. In the final stage of the installation of these types of bearings, it is necessary to accurately Adjust the clearance, that is, control the preload (load), especially for the shaft system with strict requirements on rotation accuracy, noise, and temperature rise, such as the machine tool spindle, not only to control the preload (load) to adjust the clearance during the initial installation, And it needs to be adjusted in use. There are many ways to control the preload. The following are several methods to control the preload and adjust the clearance. (1) Measure the starting friction torque of the eccentric bearing, measure the relationship between the bearing starting friction torque and the axial load in advance, and adjust the preload by controlling the starting friction torque, which is often used in the axial direction of tapered roller bearings installed in pairs Preload. (2) Measure the axial displacement of the bearing. For the tapered hole bearing, measure the relationship between the axial load and the axial displacement of the eccentric bearing in advance, so as to control the axial displacement to adjust the preload. (3) Measure the deformation of the pre-tightening spring, measure the relationship between the load and deformation of the spring in advance, and adjust the load of the constant pressure pre-tightening by controlling the deformation. (4) Measure the tightening torque of the nut, and adjust the pretightening amount by controlling the tightening torque of the nut when preloading the bearing with a nut. (5) Use the bearing end cover to add pads, which will cause one end to be tightened, and the other end of the bearing will not be put into the gasket first, and the screws are tightened. When the shaft cannot rotate freely, it means that there is no play in the shaft system. Use a thickness gauge, etc. Measure the gap between the end cover and the end face of the bearing seat, and add this value to the required clearance value to get the thickness of the gasket. (6) Using the middle spacer, the length of the inner ring spacer can be calculated from the length of the bearing outer ring spacer and the support size, and it can also be determined by actual measurement. It is difficult to detect the preload of the eccentric bearing, except for a few with special instruments. In addition, most of them use a dial indicator to measure the axial and radial displacement of the shaft or measure the starting friction torque. In order to keep the preload at the best value, some foreign bearing companies use special instruments and some structures to adjust the preload. The load is detected and adjusted to achieve controllable preload.