Learn about the radial clearance standards for rolling bearings

Bearing clearance refers to the amount of movement when the bearing is not installed in the shaft or bearing box, one side of the inner ring or outer ring is fixed, and then the side that is not fixed moves radially or axially. According to the direction of movement, it can be divided into radial clearance and axial clearance. Clearance is also very important for the use of bearings.

The radial clearance of a rolling bearing is the arithmetic mean of the radial distance of the outer ring relative to the inner ring from one radial eccentric limit position to the opposite limit position in the non-preloaded state. According to the national standard GB/T307.1-2018, radial clearance is divided into five grades: large, medium, small, very small and extra small. The clearance values of each grade range are as follows: C2, CN, C3, C4, C5; C0, C1, C2, CN; Small for C0, C1, C2, CN; The minimum is C0 and C1; The extra small ones are C0 and C1, where C0 represents a small clearance and C5 represents a large clearance.

 

In addition, the ISO standard and the American ABMA standard also have different grades for radial clearance. The ISO standard is divided into four grades: N, P, M, and K, and the American ABMA standard is divided into five grades: C1, C2, C3, C4, and C5. When selecting bearings, it is necessary to specify the criteria used to determine the clearance class.

 

The radial clearance of a bearing directly affects its service life, temperature rise, noise and vibration and other properties. Excessive clearance may lead to shorter bearing life, reduced rotational accuracy, vibration and noise; If the clearance is too small, it is easy to cause friction and heating to increase, the temperature rise to increase, and even lead to bearing locking. Therefore, when selecting the bearing clearance, it is necessary to consider the tightness of the bearing and shaft fit, the temperature difference caused by the bearing operation, and the difference in the expansion coefficient of the bearing and the shaft.

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