Re-assembling with Stainless Steel

[cobolman]

I've seen a number of posts talking about the use of stainless steel nuts, screws and bolts during a restoration. But it occurs to me that different metal types can cause corrosion. So while the stainless steel itself may not rust, it can react with other metals and lock solid.

So now, instead of having a rusty, stuck fitting, we'd have a shiny stuck fitting.

Or have I misunderstood? Is it a good idea to use stainless steel fittings when rebuilding or restoring a classic Mini?

[Dr.Mabo]

No, its not a good idea.

There is a reason why motor engineers generally calculate strenth and material on specific positions. E.g. some connections need a defined flexibility, which are not given when you change to stainless steel bolts. In terms of corrosion it can also be a step back rather than forward.

Better use clean or freshly galvanised bolts and nuts with some anti corrosion grease like copper or graphit grease.

[moita]

Don't do that, use the correct specs bolts and nuts, specially were they are used for structural purpose as they were design to a specific grade to hold the forces that could reach it.

Only on those who are not structural, like for example fixing the black cowl.. those kind of examples.

[Peter Laidler]

While I'm not a metallurgist but a plain, old and experienced 70's era mechanical engineering grad, I disagree with the gist of the above. Insofar as corrosion is concerned, then if this really worries a restorer, then a good smear of coppaslip between the thread will effectively cure this.

One only disagrees with the good Doc Mabo after a good deal of thought. And in the Doc;s line of aeronautical work, then you stick to the manufacturers specifications - without question, and I agree. But our car bodies, fixtures and fittings are just that and the torque loadings are so (relatively) small as to make absolutely no difference in the strength of the application.

My speciality is armour and mountings that would shake the living daylights out of most mechanical fixings within an hour, from post apprenticeship until - with a career break - and back again until I retired. And while I restored my Mini and wifes Dolly Sprint and a few Commandos with brand new from the MG works, BMC/BL fixings and noticed the deterioration and decline, it's been stainless since the 90's. And never looked back and NEVER experienced a corroded joint of sheared bolt.

And if you don't want shiny nuts, bolts and washers - or other parts/brackets etc etc that you've made from stainless in your workshops to replaced the rusty stuff. Just paint it black

Just me, speaking from experience. Steel helmet on (stainless of course...) and flak jacket zipped up, awaiting the incoming mortars

[Spider]

Sorry to go the other way here Pete,,,,,

Common grades of Stainless does from my experience have the issue if dissimilar metals when used with steel, it causes the steel to rust in very short time around the fastener, even here in Australia, where we don't get the rain (in the way the UK does) or salted roads. If you looked on a Galvanic Chart, you'll see that Stainless is a long way apart from (plain) steels. When the metals are closer on that chart, they are 'happier'.

Stainless Fasteners also generally have a Tensile Grade of less than 2, those used in our cars are mostly Grade 3 and Grade 5, yet despite being such a low grade, the material is quite brittle and prone to cracking.

Stainless on Stainless also galls. When you fit a Stainless Nut on a Stainless Bolt, tighten them and then try and undo them, they cold weld together.

Granted, there are compounds available to reduce the effects of corrosion and galling, but these can be messy and some are toxic.

[MiNiKiN]

I agree with the "do not use stainless steel fasteners" faction because of electro-chemical corrosion problems (as explained in more detail by Sir Spider).

I disagree with the remedy against future corrosion to apply "some sort of grease or copper paste etc".
Let us assume that the bolted joint has been calculated for the required clamping force and associated tightening torque to achieve this. The type of thread lubrication (or dry assembly) plays a very important role in such a calculation.
If a different lubricant is used, the fastener may be under- or over-tightened, resulting in a loss of clamping force, a loose joint or a seized thread. Any combination of the above can occur. The remedy is to use the recommended lubricant (usually "lightly oiled") and the correct torque.
Apply a thin layer of Waxoil to the joint to prevent water ingress.

I am sure some will say this is too academic as they have always tightened to A) hand tight or B) FT (effing tight) without any problem. I can only say that I once bought a car from such a talent - half the suspension bolts were loose when I checked them...

[Peter Laidler]

Hello Minikin. I'm your first customer to most respectfully and politely suggest that the response is too academic and based on what we used to call 'fuzzy logic. Talk of torque (if you'll excuse the pun....) loading is pretty much academic in the examples we - car restorers and rebuilders - are concerned with. The, say, up to 50ft/lbs (sorry, (I'm a imperial era engineer) don't even feature on the engineering richter scale. Not even with coppa slipped threads.

Let me give you an example. My isolastic Norton Commandos vibrate......., it's like sitting on a Kango-hammer. Nope, never had a problem yet. Not even with the stainless exhaust flanges threaded directly into the alloy cylinder head (and I accept that they're loosely wire locked).

Now, if we were talking about machine-cannon mountings on a turret, dissimilar fixing/clamping/holding materials....... Sorry, same again!

And if it's good enough for Catmint........ Maybe Cabolman ought to let his own judgement be his guide

Maybe stainless fixings ought to be put into the same category as silicon brake fluid and waterless coolant. Subjects not to be discussed in the Common Room, the Mess or in the Lodge or in polite company

[MiNiKiN]

No worries, life will go on even if we two are in disagreement on this matter. Peace!

[mk1]

Cars rebuilt using stainless usually look rubbish. Use original spec fasteners wherever possible.

[Rusty old S]

Good luck in trying to source stainless in imperial.!!

[mk1]

Good luck in trying to source stainless in imperial.!!

Not that I'd use them, but . . . .

https://www.westfieldfasteners.co.uk/UNF.html

[Nick W]

I don't use stainless nut bolts and screws on minis as they don't look original...
But after rebuilding a few landrovers over the years, I'd recommend using stainless bolts for everything on the body if your going to actually use it . Never had any of the bolts cause any issue what so ever, and 4 years after my last full rebuild, no signs of oxidising around the bolts, where as I can guarantee you all the lot would need replacing if I'd used galvanised steel bolts that last about 1 year if exposed to the elements in the UK.
Obviously don't use them on any suspension or engine mountings etc,
Anyway how would they build speed boats and Yachts without stainless fastners??

[Peter Laidler]

Like I said Mark. If a rebuilder doesn't like the shiny look, just paint 'em! That's what I do. But safe in the thought that it's non corrosive stainless undereath doing its job.

If you are looking for stainless UNF or enev BA, then look no further than EBay, under 'stainless, UNF'. Got some 8/32 just last week from a supplier in Fiskerton

[Costafortune]

Fit some stainless steel brake caliper bolts, and see what happens after a few good stops. It will literally rip the caliper off - I've seen it happen.

The biggest mistake is using copper slip on wheel bolts/nuts. They must be fitted absolutely dry, both threads and taper seat. Any lubricant on the cone taper will result in a far higher torque figure than your wrench will indicate - stretched wheel bolts = wheel falls off when they finally break.

[Polarsilver]

Costa. just as a balance to your comments re; Copper Slip on Wheel Studs & Nuts. . just saying that during my 1960,s engineering training in mechanical engineering & thereafter during my 60 odd years since using bolt torque this was part of my working life especially in construction & use of very large Cranes.. i have been using Copperslip on most anything with a thread or gasket includes exhaust manifolds & joints can say that never has Cooper Slip been a issue or problem .
I used Stainless Allen Cap Bolts on my 4 pot Calipers given it is not possible to use Hex Head Bolts on these Brake Calipers that Minispares supplied issue was due to clearance Hex Head bolt that MS supplied fouled near the Caliper making it impossible to use a Socket ..Stainless Allen Cap Bolt once fitted with copper slip has never been an issue.
The idea is select the "correct grade" bolt & nut then Torque to manufactures spec; also taking note of dry or wet instruction to suit the application. ..example slew ring bolts on cranes were dry fit 10.9 grade to very high torque that needed a Multiplier to achieve torque figure & bolts could still come loose.
Any Fixings Buy Cheap & get what you pay for.

[Nick W]

So you wouldn't think they would sell these if they weren't up to the job?.

https://www.pro-bolt.com/stainless-stee ... sfbmon490/

[Peter Laidler]

A waft of good grounding bleedin' obvious and common sense from the real, time served and truly experienmced mechanical engineers is taking shape.

Nicks example is a classic example of when to use BOLTS as opposed to SCREWS.

Fuzzy logic won't defeat the laws of physics..

[Spider]

There's Stainless and there's Stainless,,, ie, there's many different grades and types of Stainless fasteners. Most bought over the counter are typically from 304 grade (A2) and have all the tensile strength of matchwood. There are few, very expensive, grades that start to come in to the range of Grade 5 steel fasteners.

Respectfully here Polar, when things like cranes etc are designed (engineered), they types of fasteners used and how they are to be fitted is factored in and spec'ed up on the drawings for manufacture and assembly.

Nick, aren't Landrover bodies Aluminum ?

Here's a comparision of tensile strengths of many common grades of stainless fasteners to steel



https://www.assda.asn.au/blog/221-stren ... -fasteners

The lowest Grade used in Minis that I'm aware of is Grade 5 fasteners, which from that chart, the higher grades of stainless almost reach. There are many other factors of course to fasteners, but this one alone doesn't cut the mustard.

[Nick W]

Nick, aren't Landrover bodies Aluminum ?

Yes early ones were Brimabright after around 1980 they changed to a thinner alloy , chassis is painted steel, mine is galvanised.
All the landrover specialists sell full Stainless kits for them nowadays.

Nick

[Spider]

Nice - delicious in fact ! - work there Nick, cheers for sharing.

Yes, given they are Aluminum, I too in that instance would look to see what I could do in stainless too. Steel fasteners - even without the salt - would just react against the Aluminum body.