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BEARING HANDLING (Continued) ________________________________________________________________________

EXCESSIVE FORCE

The most common cause of small bearing failure is excessive force applied during assembly, which usually results in the following adverse effects on bearing performance:

Brinelling (raceway damage)
Noise
Higher torque
Changed mechanical characteristics
Reduced lifetime

Brinelling causes noise.

Excessive forces during assembly of small bearings are generated by poor handling techniques or incorrect/uncontrolled interference due to poor design or tolerance stack up.
  • NEVER press fit a bearing to a mating component by
    applying force across the bearing raceways through
    the balls. This will always result in brinelling damage
    to the bearing. Press the inner ring for a press fit on
    the shaft or the outer ring for a press fit in the housing.

  • Calculate the effect of worst-case tolerances on interference fits. Allow for thermal expansion and material type in calculating the maximum loss of radial play. Use a bearing with suitable radial play range. Loss of radial play will change the mechanical characteristics of the bearing (contact angle, torque, resonant frequency), and can ultimately cause bearing failure.

Excessive interference has cracked the inner race.
  • Follow all guidelines for mounting practices. Make sure that fixtures are aligned.

  • Bearings are susceptible to shock or impact loads, especially when the axial play has been removed
    through preload. Dropping a preloaded assembly, or even placing it on a hard surface, can cause
    brinelling. It is recommended that assembly work surfaces are covered with a layer of shock-absorbing material.
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