In machine tool applications, the rigidity of the spindle is extremely important as the magnitude of elastic deformation under load heavily influences the productivity and accuracy of the tool. Although bearing stiffness contributes to system rigidity, there are other influencing factors including tool overhang as well as the number and position of the bearings.
Factors that determine bearing stiffness include:
The rolling element type
Roller bearings are stiffer than ball bearings. Ceramic rolling elements are stiffer than those made of steel.
The number and size of the rolling elements
A larger number of smaller diameter rolling elements increases the degree of stiffness.
The contact angle
A contact angle close to the load angle results in a higher degree of stiffness.
The internal design
A close osculation results in a higher degree of stiffness for angular contact ball bearings.
In applications requiring a high degree of radial rigidity, cylindrical roller bearings are typically the best option. However, angular contact ball bearings with a minimal contact angle can also be used.
In applications where a high degree of axial rigidity is required, angular contact thrust ball bearings with a large contact angle are preferred. Rigidity can be increased by preload, but this can limit the permissible speed.
For additional information about system rigidity and bearing stiffness, refer to System rigidity.