What types of bearings need preloading during installation and how? I have seen angular contact ball bearings preloaded by locknuts and deepgroove bearings by curved washers or belleville washer or end caps but where and how much? Do any guidelines exist for that and if not properly preloaded , what may be consequences,and how to diagnose?
Regards everybody.

Have you searched internet e.g. SKF website to look for articles on this subject?

Searched internet but with little success. Any consolidation of such information will be helpful.
Regards.

The decision to preload a bearing depends a lot on the application. Not all bearings should be preloaded.

From our company manual it lists the following reasons to preload a bearing:

- enhance stiffness
- reduce running noise
- enhance the accuracy of shaft guidance
- compensate for wear and settling (bedding down) process in operation
- provide long service life.

I'm not sure of the reasons to provide clearance, but I imagine that temperature fluctuations of the bearing or (more importantly) the shaft have something to do with it.

IMHO; none! an A-F brg needs no metal interference or -clearance or whichever term you wish. If You have no clearance in an AF brg then it's a shortened bearing life. How close you can approach zero clearance is dependant on the ABEC#. A #9 can basically approach zero as it is aircraft quality.

35 years ago at Kodak we would preload some bearings that required no spindle movement. Some run-out may have existed but it wasn't compounded. This did however require regular bearing replacement.