Below the caution statements are recommendations for shaft and housing fits for a number of different applications and a table of recommended shoulder diameters for select NHBB part numbers.

It is relatively easy to damage a miniature and instrument bearing during assembly simply by exceeding its load capacity. Adequate fixturing must be provided for handling and assembling precision bearings to ensure that:

If the outer ring or inner ring face will be clamped or abutted against a shoulder, make sure the shoulder configuration provides a good mounting surface:

Portable High Pressure Grease Bucket Hand Operated Grease Pump. Provides high pressure greasing, where power is not available or when an air operated grease pump cannot be afforded.

Interference fit

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Bearinghousing tolerance

When miniature and instrument bearings are interference fitted (either intentionally or as a result of thermal gradients) the bearing radial play is reduced by an amount equal to approximately 80% of the actual diametral interference fit. Thus:

H8 tolerance

The bearing will be subject to early failure in most applications because it may already be overloaded. This problem can be solved either by a higher radial play or looser fit.

Accurate shaft and housing fits are important for proper bearing installation and operation. In ordinary applications, miniature ball bearings are used with a light load, so a light interference fit to a narrow clearance fit is usually sufficient. Light cross section bearings, such as Torque Tube and Thinex bearings, are more sensitive to shaft and housing imperfections and require looser fits than heavier cross section bearings.

Fit tolerance

New Hampshire Ball Bearings, Inc. (NHBB) is a leading manufacturer of precision bearings and complex bearing assemblies for the global aerospace, defense, medical, and high technology markets. The company is a subsidiary of MinebeaMitsumi Inc. and an integral part of the global brand, MinebeaMitsumi Aerospace.

A bearing that is fitted too tightly or too loosely, or is damaged during assembly by excessive force or shock loading, may degrade the performance of your assembly. Reduce this possibility by following some general guidelines during the design of mating parts and by observing the following four cautions during the assembly process.

When establishing shaft or housing sizes the effect of differential thermal expansion must be taken into account. If thermal gradients are present or dissimilar materials are used, room temperature fits must be adjusted accordingly. Approximate thermal coefficients for common materials are available from NHBB.

L = Loose fit.T = Tight fit.d = Bearing bore as listed.D = Bearing OD as listed.+Bearings must be purchased with bore and OD coding. Example: To use SSR-2 bearing in a potentiometer, the shaft diameter should be .1250 –.0001 to .1250 –.0003 or .1249 to .1247. The housing should be .3750 +.0002 to .3750 –.0000 or .3752 to .3750.