Useful Stainless Site

[lemmingzappa 75 1 Cars]

I bought some stainless 14mm bore washers for my top mounts, a few jubilee clips for the engine bay and some nyloc nuts. Just thought i'd share the link with you as the prices seem reasonable and the postage is super fast.

 

http://www.a2stainless.co.uk (Stig's Fasteners)

 

Useful for bits you may need.

[SurGie 54]

That's useful for me, thanks for that.

[MerlinGTI 3]

Another good one (Ive ordered from here with no probs)

 

http://www.stagonset.co.uk

[Jrod 7]

For lightweight alloy bolts I use: http://www.hyperbolt.com/

 

Good for non load critical bits that can be light and pretty.

[MerlinGTI 3]

Nice one Jrod, handy that

[Beastie 1]

Thanks for posting that, Lemmingzappa! Nice prices! Much cheaper than Namrick for UNF and BSF fasteners... and as it happens I'm overdue for a restock on just those items so I'll give them a try

[Cameron 16]

Make sure you use a good anti-sieze on stainless fasteners if you ever want them to come apart again. You wouldn't believe how quickly they'll seize up and when they do, that's it, they'll never come off.

[Beastie 1]

Make sure you use a good anti-sieze on stainless fasteners if you ever want them to come apart again. You wouldn't believe how quickly they'll seize up and when they do, that's it, they'll never come off.

 

Interesting - that's never happened to me as yet. I only usually use them for bodywork fasteners though so perhaps it's a heat issue? The one exception to this was a set of manifold studs which I made in stainless when I overhauled a MK6 Bentley some years ago. The originals were mild steel and they use deep brass nuts with a plain section machined below the hex in order to clear the casting. They always sieze solid and shear the studs if you don't cut the nuts off them which is a pain since the manifolds have to be removed every time you set the exhaust valve clearances. The stainless ones need regular re-tightening though because the brass nuts continually come loose - although the owner who does his own maintainance prefers this to the siezing. There are too many factors to be sure of what's happening without experimentation though: Brass against stainless being one and another being the BSF threads which don't have the self locking action of the ISO metric thread.

[Cameron 16]

It's happened to me a few times, especially when using stainless fasteners in mild steel, or vice versa. No heat involved, just unscrewing bolts that had been lightly tightened, it goes a few turns then suddenly just bites and that's it! The first time it happened to me I couldn't believe it, it was an M6 thread and I was wrenching on it with a long T-bar allen key and it just wouldn't budge!

 

Apparently it's something to do with the stainless fastener galling microscopically when it's undone from being tight, then once they catch on part of the thread they pretty much weld themselves in place. It's interesting but bloody annoying! Not sure about stainless in aluminium or other metals, but I assume the same applies.

Edited June 18, 2010 by Cameron

[Rippthrough 98]

Aluminium is the same, use grease.

Aluminium + stainless together form a galvanic circuit and corrode together so use copper anti seize between those*

 

It's because both aluminium and stainless steels form a thick oxide layer on the surface (which is what protects them against further corrosion), when you tighten them up or rub them against each other the wear on the surfaces (even 'smooth' surfaces have very little actual surface contact - in the order of less than 1% - imagine loads of peaks and valleys sliding across each other with huge pressure) breaks the oxide film on the peaks as they slide and the reactive metal underneath effectively spot welds itself together.

 

The problem is no matter which way you then turn the bolt - tightening or undoing - the oxide film is broken where the weld is and further movement just serves to make the weld bigger and bigger...

 

Stainless bolts + nuts = grease

Aluminium bolts + nuts = grease

Stainless bolts into large aluminium structures = copper anti-sieze*

Aluminium bolts into large stainless structures = don't do it, corrodes from the galvanic circuit formed.

 

 

 

*The copper won't stop galvanic corrosion, but instead of occuring between the aluminium + steel it'll occur between the aluminium and the grease, and the steel and the grease - so the ally + steel don't get welded together from it...

You can get specialist sealing compounds which'll actually prevent it if you want to splash out though...although it's not as bad as it sounds, the anodising on the ally prevents most of it (insulator - unless you've broken the film from galling....), as will passivation on stainless.

 

Low strength loctite works well too - I've got a farkoff big bottle of the penetrating stuff just for this...

Edited June 18, 2010 by Rippthrough