The clearance of rolling bearings refers to the maximum radial or axial movement of another ring when one ring is fixed, and is divided into two types: radial clearance and axial clearance. When assembling rolling bearings, the clearance should not be too large or too small. Excessive clearance can reduce the number of rolling elements that can simultaneously bear the load, increase the load on a single rolling element, thereby reducing the rotational accuracy of the bearing and shortening its service life.
A small clearance will increase friction, lead to an increase in heat, exacerbate wear, and also reduce the service life of bearings. Therefore, strict control and adjustment of clearance are required during bearing assembly. Pre tightening refers to applying an axial force to the inner or outer ring of a bearing during assembly to eliminate clearance and cause initial deformation at the contact between the rolling elements and the inner or outer rings. Pre tightening can improve the stiffness and rotational accuracy of bearings in working conditions. For bearings that bear large loads and require high rotational accuracy, they usually work without clearance or with a small amount of interference, which requires pre tightening adjustment during assembly. The adjustment and pre tightening of clearance are usually achieved by making appropriate axial relative displacement between the inner and outer rings of the bearing.
Before installing bearings, the bearings, shaft necks, and bearing seat holes should be cleaned thoroughly. During installation, use specialized tools to press the bearing flat and evenly, avoiding direct impact of hard objects such as hammers on the bearing. If there are no specialized tools, a copper or wooden rod should be used as a cushion, and then hammered to ensure that the pressure is evenly distributed on the inner and outer rings of the bearing, avoiding unidirectional pressure and preventing the bearing from tilting, damaging the mating surface, or installing eccentricities.
During the installation of bearings, if it is found that the fit between the bearing neck and the bearing seat hole is too tight or too loose, the installation should be stopped and a suitable bearing should be selected for reinstallation. If there is a deviation in the journal or bearing seat hole, it should be repaired before installation.
After installation, the machine should be started to measure the temperature of the bearing housing and listen for its sound. If the temperature is too high, it indicates that the clearance is too small; If the sound is abnormal, it may indicate excessive play. According to the inspection results, adjust the clearance after stopping the machine.
When disassembling bearings, special attention should be paid to not transmitting pressure through the rolling elements to avoid damaging the bearing cage. Try to use a puller to slowly disassemble the bearing. If there is no puller, a copper or wooden rod can be used as a cushion and gently hammered to disassemble, while being careful not to damage the surface of the shaft neck or bearing seat hole.