Bearing tolerances are generally H7 for the inner ring and h6 for the outer ring.
Generally, the tolerance for the inner ring bore of a standard bearing is H7, and the tolerance for the outer ring is h6. The fit between the inner ring and the shaft is H7/h7 or H7/js6 (bore-basis system), and the fit between the outer ring and the housing bore is H7/h6 or JS7/h6 (shaft-basis system).
The fit between a linear bearing and a guide shaft is H7/g6 (bore-basis system), and the fit between the linear bearing bushing and the mounting hole is H7/h7 (shaft-basis system). Note that the fit tolerances may differ slightly depending on the positioning datum.
Methods for determining shaft tolerance grades:
1. Taking a standard grade (P0 grade) 6308 bearing as an example:
The outer ring tolerance can be found in the bearing tolerance table: Upper tolerance: 0, Lower tolerance: -0.011.
2. Based on the bearing's rotation method and load-bearing method:
The outer ring is generally fixed relative to the inner ring, and the load-bearing capacity is fixed load, not the primary load. Based on this information, the recommended fit table for the housing bore shows that for bearings using bearing housings, the recommended housing bore tolerance zone is H8. The H8 tolerance zone has an upper tolerance of +0.054 and a lower tolerance of 0, indicating a clearance fit. The maximum clearance is 0.065, and the minimum clearance is 0.
3. Fit between the bearing inner ring and the shaft:
The tolerance for the 6308 bearing inner ring is: upper tolerance 0 and lower tolerance -0.012. Based on the inner ring rotational load and normal load, the recommended shaft fit tolerance zone is m5, with an upper tolerance of +0.020 and a lower tolerance of 0.009. This indicates that the maximum clearance is 0.020 and the maximum interference is 0.003.
