Bearing Mounting and Fitting: Bearing Failure Due to Bearing Force, Moisture, and/or Poor Alignment || Dynaroll Bearing Design Factors Part 2

Avoid excessive force: The most common cause of small bearing failure is excessive force applied during assembly, which usually results in noise, higher torque, raceway damage, etc. Excessive forces during assembly of small bearings are usually 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 shaft press fit or the outer ring for housing press fit.
  
• 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.
  
• 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 pre-loaded 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.

Avoid moisture and high humidity: Bearings are susceptible to corrosion and should be kept in a dry environment. The lubricant in a bearing will provide some measure of corrosion resistance to the internal raceways, but the acid from skin can corrode the outer surfaces. 52100 chrome steel bearings will quickly corrode if the lubricant is cleaned out, so bearings made from this material should never be used dry.

Bearings must be aligned in an assembly: Misalignment during assembly is a common cause of
bearing noise, increased torque, and general poor performance. The free angle of misalignment that a small bearing can tolerate is typically less than 1°.

 ½ Must be < uf

• Locating shoulders on mating components must be parallel to bearing raceway faces.
  
• Shaft and housings must be concentric. This is particularly true when more than 2 bearings share a common component.

This is the second article in a series of four on design factors when using small bearings.

Go to Bearing Design Factors, Part 1: Bearing Geometry Design and Technical Information