Conical washers vers Plain Washer with Spring Washer

Take a quick look here:

With metric hardware a type of wave washer is frequently used. If vibration is a problem look at Nordlock washers. Nordlocks tighten as the bolt or nut tries to loosen.

If heat is not an issue why not look at looking at nylock nuts. They have a nylon insert that "jams" the threads - preventing the loosening of the nut. Doesn't require special tools, can be reused numerous times, and dispenses with the requirement for additional lock type washer.

Len

Cam Jacks> My machines are mostly fixed together with hex head screws or bolts with

One advantage for using Belleville washers in place of either flat or lock washers is they tend to maintain the preload exerted on the joint system so long as the bolt and joint deformations are relatively small. Better yet, increase the fasteners length to diameter ratio to reduce stress, fatigue failure and loss of preload.

Kman

Interesting comments guys. Thanks for the feed back.

When it comes to properly designed highly stressed threaded bolts, the first year mechanical engineering "Statics and Strength of Materials" books and courses go over the theory of how to size a bolt very well for the range of forces a bolt must endure, and also how much torque must be used to pre-stress the bolt correctly.

I don't design highly stressed machinery, so I have forgotten much of what I read, but if I had to design those things again, I would reread my old stuff and search out new articles to be sure I did it right.

Bo

Good reference for this information is "An Introduction to the Design and Behavior of Bolted Joints", Author John H. Bickford

Kman

It's a really thorny issue, making bolted joints that won't vibrate undone.

One thing to note, is that some people feel (backed up by test results) that spring washers actually make things worse. If you look at catalogues for slewing ring bearings, they usually say they will not necessarily honour the guarantee if spring washers are used, and you must use solid, hardened washers.

I think the Nordlock type of serrated/cam-action type seem well thought of, and my other recommendation would to use an appropriate grade of Loctite thread-locking adhesive.

Otherwise, the correct size/number/length/torque of bolts will do the job in most applications.

Regards, John H

Actually, washers are supposed to make the torquing of bolts more consistent by providing a hard consistent surface to put load against.

Variable bolting surfaces like castings and varying amounts of corrosion make for totally unknown torque loads to get the desired preloads.

Bo