Preload of Angular Contact Bearings
Reasons for preloading bearings:
Eliminate radial and axial play in the bearings
Increase the spindles rigidity
Eliminates non-repetitive run out caused by bearing looseness
Prevents skidding of the rolling elements
If done incorrectly:
Excessive preload causes heat in the bearing drastically reducing its lifespan
Excessive preload increases the energy required to rotate the spindle
Under preloaded bearings cause the rolling elements to skid. This damages the raceways and the rolling elements causing premature failure
Under preloaded bearings cause looseness of the shaft resulting in poor part finish and the inability to hold tolerances.
Under preloaded bearings will often generate noise while the spindle is running
Methods of spindle repair bearing preload:
Install a duplex bearing set with previously adjusted stand-out dimensions and axial clearance
Use a spacer to obtain the correct offset
Use a force generated by spring tension
Use nuts to adjust axial preload by torque (This is a poor design for spindle applications)