Bearing fit refers to the radial or axial positioning in which the inner diameter of the bearing and the shaft, the outer diameter of the bearing and the mounting seat hole must be reliably and evenly supported in the whole circle direction. Generally speaking, there must be a proper amount of interference before the bearing ring can be fixed in the radial direction and supported adequately. If the bearing ring is not properly or fully fixed, it is easy to cause damage to the bearing and related parts. The dimensional tolerance of shaft and housing hole of metric series has been standardized and can be selected from ISO standards. The fit between the bearing and the shaft or housing can be determined by selecting the dimensional tolerance.

When selecting cooperation, in addition to fully considering various service conditions, the following important factors should also be considered:

★ nature and size of load (rotation differentiation, load direction and load nature)

★ temperature distribution during operation

★ internal clearance of bearing

★ processing quality, material and wall thickness structure of shaft and shell

★ installation and disassembly methods

★ is it necessary to use the mating surface to avoid the thermal expansion of the shaft