Bearing stiffness

The stiffness of a rolling bearing is characterized by the magnitude of the elastic deformation (deflection) in the bearing under load. It is expressed as the ratio of load to deflection and depends on the bearing type, design and size. The most important parameters are:
  • type of rolling elements; roller bearings have a higher degree of stiffness than ball bearings because of the contact conditions between the rolling elements and raceways
  • rolling element material (diagram 1)
  • number and size of rolling elements
  • contact angle (diagram 2)
  • preload class (diagram 3)
Bearing stiffness can be further enhanced by applying a preload (→ Bearing preload). Preloading bearings is standard practice in machine tool applications.
A loose fit on a mating component can have a negative influence on the stiffness of a bearing arrangement. However, a loose housing fit may be necessary for bearing arrangements using angular contact ball bearings in the non-locating position. Typically the non-locating bearing position is on the non-tool end of a spindle shaft and, therefore, the influence on system rigidity for the tool end is limited. If a high degree of stiffness is also desired for the non-tool end, a cylindrical roller bearing with a tapered bore should be used. This arrangement can accommodate axial displacement of the spindle shaft relative to the housing within the bearing and enables an interference fit for both the inner and outer rings.
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