Rotary bearings are machine elements that support rotating shafts accurately while providing low friction conditions. In order to maintain a stable bearing performance over a prolonged duration, appropriate bearing fit design considerations are required to avoid any negative effects [Chart 1] that may arise from bearings‘ rotary operation.
|Issue||Side Effect||Proposed Solution|
|Significant temperature increase due to high speed rotation||Shaft diameter may expand causing moment loads, resulting in bearing seizure, and uneven wear.||Choose fitting dimensions with the anticipation of shaft expansion.|
|Thrust and radial direction clearance variations occurring from applied loads.||Degradation of rotational accuracy. Abnormal noises.||Choose fitting dimensions with anticipation of reformed clearances under load.|
Design Example of Rotary Bearing Applications
The example seen in [Fig. 1] is based on “Inner race rotation/outer race retained”.
Selection of Bearing Fits Based on Shaft Diameter
Transition fit or interference fit is selected to ensure the shaft and the inner ring will always rotate together.
|Shaft/Bearing Fits||Applicable For||Fit Standards|
|Transition Fit||For light or varying loads||h5|
|Interference Fit||For general applications||js5|
Selection of Fits for Bearing Holder Bores
Clearance fit should be chosen for ease of assembly while preventing any deformation of bearings‘ outer/inner races. In general, a Clearance fit (H7) is used. In case of light loading applications (H8) can be used, or (G7) when large temperature variations are to be expected.
|Bore Fit Selection||Applicable For||Fitting Standards|
|Clearance Fit||General rotation applications||H7|
|Clearance Fit||Light loads||H8 (wider tolerance than H7)|
|Clearance Fit||Significant temperature increase||G7 (large clearance)|
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