1. Preload of bearing

1.Purposes of preloading
1)	To improve bearing positioning accuracy in both the radial and axial directions and rotation accuracy by suppressing shaft deflection (vibration).
2)	To improve gear engagement accuracy by increasing bearing rigidity.
3)	To reduce the possibility of failure, such as smearing, by suppressing the sliding of rolling elements.
4)	To prevent noise that may be caused by vibration and resonance.
5)	Keep rolling elements in place with respect to the bearing rings.

2.Preloading methods
Bearings can be preloaded by the locating method or by the spring method. Typical preloading methods are given in the table.
1)	When the size of the preload is the same, the locating method produces a smaller deflection in bearings than the spring method if the bearing is exposed to an axial load. This results in a high rigidity.
2)	When the spring method is used, the spring absorbs load variation or shaft elongation and contraction, making it possible to apply the preload stably with minimum variation.
3)	A greater preload is achievable when the locating method is used.

3.Typical preloading methods