Ball Bearing Mount/Housing Hardness

[mtipg]

Hello All;

I have a question concerning the hardness requirements for a ball bearing housing or shaft mount. Is there a minimum hardness for the shaft or housing to make sure that when a bearing is installed it receives the right amount of crush? Does the hardness matter?

 

[flash3780]

I think you may be confusing hardness with elasticity. Materials of different hardnesses can have similar modulii. The hardness of the bearing housing is important in that you want to make sure that the fatigue life of the material meets the requirements of your design. Harder materials can have less predicable fatigue life (esp over Rc 35).

The place where hardness really matters is in the interface between the rolling elements and the raceway. Bearing elements and raceways tend to be extremely hard, with induced compressive stresses to help close any cracks that may form in the surface.

 

[Fugeguy]

Rc = 30 minimum (for a press fit)
Rc = 58 minimum (for a surface the roller element is going to run on- think needle)
Rc = material if a slip fit

Increase hardness for a heavy press fit and lower for lesser press fits.

Roughness of .8a to 1.6a for less than 40mm id bearings and 1.6a to 3.2a for 40 mm id and above.

 

[flash3780]

Rc = 30 minimum (for a press fit)
Rc = 58 minimum (for a surface the roller element is going to run on- think needle)
Rc = material if a slip fit

Increase hardness for a heavy press fit and lower for lesser press fits.

Roughness of .8a to 1.6a for less than 40mm id bearings and 1.6a to 3.2a for 40 mm id and above.

All correct, but they don't affect the amount of crush. The class of fit is determined by the ratio of the applied load to the bearing basic load rating. Section 3.2.2 of Harris' Essential Concepts in Bearing Technology gives further details.