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Self-locking nuts and bolts

6591 Views 9 Replies 7 Participants Last post by  503865
I've been working on my Benz, following the shop manual instructions. It seems that every bolt and nut is the self-locking variety, and available mainly through the dealer at exorbitant prices. To be honest, I had never heard of such beasts, so I did a little research. Actually, they do exist, and the science behind them is quite sound. Those Benz engineers do know what they are doing. Here is a very useful link, and video clip:

Vibration Loosening of Bolts and Threaded Fasteners

The article states that "...the chemical locking category provides the greatest resistance to vibration loosening...". Perhaps, hardware nuts and bolts with Loctite will do the trick?

Does anyone have any information on this?
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Each has their respective place and purpose, and personally I would not use loctite where a locking fastener is called for. I'm not an engineer and as you note MB knows what they are doing, so it's a bit illogical to think they wouldn't specify one over the other for a functional reason.
Locking fasteners can be pricey...but unintended disassembly is decidedly more costly.
Fasteners are complex beasts that comprehend a family of technologies to apply, design, evaluate, and fabricate. It is a particular area where I'd not say I'll never do or use X.

Perhaps you are not aware but thread sealant products, among which are the Loctite's, come in quite an assortment of varieties which run from the ones for fasteners to be disassembled without effort, to those that may require the heat of a torch to loosen up the mating threads (e.g. Loctite blue). The problem with liquid fastener locking products is that they may need to be applied by hand and/or that they may contaminate an incompatible joint or assembly.

As for the other varieties of self locking fasteners, the teethed washer head screws or nuts are the most dependable, from a reusable stand point. Deformed thread fasteners, or those with locking inserts, is worth to replace them whenever we take them apart. So, it can become expensive if instead of purchasing them at a shop like Universal Fasteners, or McMaster Carr, you purchase them from your local stealership. Whichever way you go, make sure the markings on the fastener match or exceed the ones you removed.

Cheers, JV :thumbsup:
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