Rotary Bearing Fits and Tolerances

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.

IssueSide EffectProposed Solution
Significant temperature increase due to high speed rotationShaft 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.
[Chart 1] Common Issues & Solutions

Design Example of Rotary Bearing Applications

The example seen in [Fig. 1] is based on “Inner race rotation/outer race retained”.

[Fig. 1] Inner race rotation with 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 FitsApplicable ForFit Standards
Transition FitFor light or varying loadsh5
js6
k6
Interference FitFor general applicationsjs5
k5
m5
m6
[Chart 2] Selection Example of Fits (Radial Bearings)

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 SelectionApplicable ForFitting Standards
Clearance FitGeneral rotation applicationsH7
Clearance FitLight loadsH8 (wider tolerance than H7)
Clearance FitSignificant temperature increaseG7 (large clearance)
[Chart 3] Fit Selection Examples For Bores (Radial Bearings)

For further assistance in selecting the correct bearing, check out 2 of our tools:

1 – Bearing Finder: Allows you to easily select your bearing, compare pricing and lead times.

2 – Bearing Calculator: Input your application requirements and get options for the appropriate bearing.

About the Author

Carlicia Layosa

Carlicia is a Product Marketing Engineer at MISUMI. She holds a bachelor's degree in Mechanical Engineering and a master's degree in Energy Engineering from the University of Illinois at Chicago. She is a Certified SOLIDWORKS Associate, Marketo Certified Expert, and is passionate about education and training.

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