When the operating clearance in a bearing arrangement is too large, the load carrying capacity of both bearings cannot be fully utilized. Excessive preload increases friction, which increases the amount of frictional heat and reduces bearing service life.
The axial internal clearance of matched bearings arranged face-to-face or back-to-back (table 1) provides an appropriate operating clearance when the bearings are mounted on shafts machined to:
- d ≤ 50 mm → m5Ⓔ
- 50 mm < d ≤ 140 mm → m6Ⓔ
- 140 mm < d ≤ 200 mm → n6Ⓔ
- d > 200 mm → p6Ⓔ
SKF recommends these shaft seat tolerance classes for rotating loads on the inner ring where P ≤ 0,06 C. If tighter fits are selected, be sure that the bearings are not preloaded and are able to rotate freely. The reduction of internal clearance caused by axial locating forces should also be taken into consideration.
For stationary outer ring loads, SKF recommends housing bore tolerance classes J6Ⓔ or H7Ⓔ.
When mounting matched tapered roller bearings, the bearings should be rotated so that the rollers assume their correct position, i.e. the large end face of the rollers should be in contact with the guide flange.