Bearing clearance refers to the amount of movement when the inner ring or outer ring of the bearing is fixed when it is not installed, and then the unfixed side moves radially or axially. According to the direction of movement, it can be divided into radial clearance and axial clearance. The size of the clearance during operation (called working clearance) has an impact on the rolling fatigue life, temperature rise, noise, vibration and other properties of the bearing. The radial clearance of rolling bearings is generally divided into groups /C1, /C2, /C0, /C3, /C4 and /C5. Groups 1 and 2 are small clearance groups; group 0 is the standard group clearance; groups 3, 4, and 5 are larger clearance groups. The selection of rolling bearing clearance groups should be based on the product type, size, operating temperature, and the tightness of the fit with the shaft and hole, etc. according to the corresponding standards. Of course, this is an issue that should be determined when selecting equipment. The detection of clearance must also be carried out professionally in accordance with relevant industry standards.