RotoPrecision Miniature and Instrument Bearings

Shaft and Housing Fits

All the effort expended in selecting or designing the perfect bearing for your application can be wasted without equal consideration given to the design of the components onto which the bearing will eventually be assembled. Issues to consider when planning shaft and housing fits are operating conditions such as load, speed and vibration; provisions for axial expansion, thermal expansion of components, the need for rigidity or rotational accuracy and assembly considerations.

Before deciding upon tight interference fits, it is important to consider their effect on radial play, contact angle, and preloads. Radial play is reduced by approximately 80% of an interference fit. Thus an interference fit of .0002” would decrease internal radial play by as much as .00016”. This could be exaggerated with the presence of thermal expansion of components.

When press-fitting a bearing, always apply forces directly on the ring being fitted so as not to transfer force between the raceways through the balls. Also recognize that inaccuracies in component geometry can be transferred to the bearings through interference fits. Where an interference fit is needed and anticipated in bearing design, it is generally applied to the rotating ring. The stationary ring is fitted loose for ease of assembly.

Loose fits are also recommended for one bearing of a two bearing system to avoid preloading caused by thermal expansion during operation, unless already anticipated elsewhere in the bearing design. Also, where loose fits are used, other methods of clamping or loading against the shoulder is ideal. In spring preload assemblies, bearings require a loose fit to ensure that the spring remains operational.

In all cases, care must be taken to ensure proper tolerances and workmanship on mounting surfaces for both the shaft and housing.

For any additional information or for immediate assistance,
please contact Application Support.
 


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