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Tolerance fit between bearing and shaft, bearing and hole Part 2

2022-08-04

 03 Tolerance standard of bearing and shaft fit
 
①When the bearing inner diameter tolerance zone and the shaft tolerance zone form a fit, the tolerance code that is originally a transition fit in the general base hole system will become an over-win fit, such as k5, k6, m5, m6, n6, etc., but the over-win amount is not Large; when the inner diameter tolerance of the bearing is matched with h5, h6, g5, g6, etc., it is not a clearance but an over-win fit.
 
②Because the tolerance value of the bearing outer diameter is different from the general reference shaft, it is also a special tolerance zone. In most cases, the outer ring is fixed in the housing hole, and some bearing components need to be adjusted according to the structural requirements, and their coordination is not suitable. Too tight, often cooperate with H6, H7, J6, J7, Js6, Js7, etc.

 
Attachment: Under normal circumstances, the shaft is generally marked with 0~+0.005. If it is not often disassembled, it is +0.005~+0.01 interference fit. If you want to disassemble frequently, it is a transition fit. We also need to consider the thermal expansion of the shaft material itself during rotation, so the larger the bearing is, the better the clearance fit is -0.005~0, and the maximum clearance fit should not exceed 0.01. Another one is the interference of the moving coil and the clearance of the static ring.
 
Bearing fits are generally transition fits, but interference fits are optional in special cases, but rarely. Because the match between the bearing and the shaft is the match between the inner ring of the bearing and the shaft, the base hole system is used. Originally, the bearing should be completely zero. When the minimum limit size is matched, the inner ring rolls and damages the surface of the shaft, so our bearing inner ring has a lower deviation tolerance of 0 to several μ to ensure that the inner ring does not rotate, so the bearing generally chooses transition fit, even if Even if the transition fit is selected, the interference should not exceed 3 wires.
 
The matching accuracy level is generally selected at level 6. Sometimes it depends on the material and processing technology. In theory, level 7 is a bit low, and if it is matched with level 5, grinding is required.