Author Topic: Upgrade to Stainless Steel or Down?  (Read 369 times)

Online Steveba10

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Upgrade to Stainless Steel or Down?
« on: 27.10. 2020 20:57 »
I’m all for substituting mild steel for stainless where prudent.
Both for its aesthetics and anti-corrosive properties.
I’m tolerant of its sheen not quite approaching that of chrome and value it’s low maintenance qualities.

I have sleeved fork seal holders and stanchions, substituted headlamp and mudguard bolts, made brackets for instruments and headlamp all with 316 or 304 stainless. I feel it’s worth the effort to polish these components as they will stay bright.
But I’ve always been wary of using stainless on stressed items.

I always remember the comparison with ordinary steel where it corrodes visually and then inwardly before weakening and failure.
Stainless corrodes invisibly inside and will fail suddenly with no surface imperfection.
It’s called Stress Corrosion Cracking (SCC) and is hastened by the presence of chlorine a chemical component of common salt.

For the above reason stainless is not used for stressed components such as spindles, suspension or engine parts.
Also it’s yield point is usually very close to its Ultimate Tensile Strength giving no warning of overload, just fracture. Common stainless is rated 70 denoting it’s UTS is around 7 compared to the 8 of lower grade ordinary bolts. The 0 designates the refusal of the manufacturer to designate a specific yield value.
Mild steel bolts are designated say 8.8, 10.9, 12.9 etc increasingly high tensile. The number after the decimal point denotes the yield value, the number in front is the UTS.
70 is relatively soft and liable to snap without warning.

So I like my machines bright and shiny and stainless fits the bill, but where do you draw the line for both safety and reliability.
It’s easy to get carried away as I did recently.
 I’d just modified some incredibly cheap stainless mudguards from China ( 3 for £19 ) made stainless brackets from tube with drilled pressed flat ends. My rims are stainless and I had polished the alloy hub bright.
The front end now looks great all except for the manky front brake actuating lever, but wait, didn’t I see a stainless one for A10s advertised on e-bay?
 Yes I did and identical design to the original except 3/4” longer for extra leverage!

I bought one, it was the same length as my original so not too happy about that, I was looking forward to using lighter effort.
But then maybe I got my brain in gear.....

How can something of the same dimensions, or longer, of inferior strength material and subject to stress corrosion be a safe substitution for a manufacturer’s item?
Especially given that manufactures pare material to the minimum for low cost and weight.

Supposing I survive the accident how do I explain to the insurance company or to the grieving relatives of my victim(s) that I substituted this safety critical item just for the sake of a bit of bling?
It’s indefensible.

I thought perhaps this was an isolated item that I came across, but no, there are many advertised and not just brake levers but spindles, torque arms etc.
Nothing to say these items had been tested, beefed up, or certified.
The best I could find was from my seller “tested on my bike,”—- so must be alright then!

I think it’s at least a bit worrying, given that in the absence of MOTs for classic vehicles the onus for keeping roadworthiness sits squarely on the owner.
Thanks for reading,
Steve.

Online berger

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Re: Upgrade to Stainless Steel or Down?
« Reply #1 on: 27.10. 2020 21:28 »
good points steve but I think the brake cable would fail before any stainless brake arm. I made my back foot rest mounts out of some sort of slightly magnetic stainless, it was brilliant at work hardening when being drilled but fairly easy to bend both ways on the same line without breaking

Offline RDfella

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Re: Upgrade to Stainless Steel or Down?
« Reply #2 on: 27.10. 2020 21:32 »
Having used stainless extensively (type 316) over several decades, I agree with much of what you say. I wouldn't use it for safety-critical items (eg wheel spindle) but, on the other hand, virtually all boat propeller shafts are stainless (a few are Monel) and I've only ever know one break. I also had a waterpump drive shaft fail on my boat last year - 'twas slightly corroded on the outside but when it sheared it was black right through the cross-section. And remember stainless doesn't like a steep temperature gradient and will corrode if denied oxygen (eg a stainless bolt through wood in a marine environment). But I'd be happy to use it (and do) for things like brake arms, because the load safety factor must be a hundredfold. You ain't gonna stress a brake hub lever or anchor with the puny force a 2mm bowden cable will exert.
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Online Jules

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Re: Upgrade to Stainless Steel or Down?
« Reply #3 on: 27.10. 2020 23:26 »
 316 SS I agree with you RD, but lots of the SS in the marketplace now from Chinese components is a much lower version, maybe not even 304 since it seems to rust reasonably readily (and is magnetic as Berger says), but it is so much more malleable than 316. In the case of the brake lever surely the most sensitive point of "failure" would be the drive spline, rounding off, rather than the lever actually fracturing, unlikely if the bolt is kept tight but still creating no brake if it did that - anymore so than the normal mild steel bracket??maybe, maybe not......

Online Brian

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Re: Upgrade to Stainless Steel or Down?
« Reply #4 on: 28.10. 2020 02:06 »
We should probably shift this topic to general discussion but I'll keep going as it is.

I have been using Stainless for about 30 years now and about 90% of what I make is in Stainless. I have used just about every grade there is but have been using 304 exclusively for about 10 years.

I have made just about every component for a bike you could think of, I built a plunger A10 a few years ago and made every part out of stainless, all the bolts, axles etc etc. I've attached a pic of the rear axle I made for that particular bike. I have never had a failure or any component that looked like it could fail. I've also attached a pic of a couple of bits I made for my veteran Triumph the other day. Once the stainless is polished it looks just like nickel plating.

I have no problem using it for what could be considered stressed parts, eg. axles. Quite often when a component fails it is not due to the incorrect use of material but poor machining. For instance with axles you never use a sharp tip tool, always use one with a radius on the nose.

There are things to learn when using stainless, galling (picking up) is one of them but once you know whats likely to happen its not a issue. If you do work with stainless never seize is essential.

Probably the biggest hurdle is one that Jules touched on and that is knowing just what grade of stainless you are working with, its quite common to buy some 304 and when you get it home and start machining it find out its 316 or another grade. I have found a lot of engineering supply places dont know the difference and have their colour codes mixed up. I recently bought a length of 304 but when I got it home I am fairly sure it is 316L.

On the subject of rusting 316 is more rust resistant than 304 hence its common name of Marine grade but it is harder to work with and I dont think the benefit of the extra corrosion resistance are needed. Having said that I live in Australia and we dont have to deal with salt on the roads and the lousy climate a lot of you live in.


Online KiwiGF

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Re: Upgrade to Stainless Steel or Down?
« Reply #5 on: 28.10. 2020 03:54 »
A couple of points that may help, not all stainless is non magnetic, the “austentic” grades (which includes 304, 316, 321) are non magnetic.

316 has superior resistance to chlorides (eg salt) and is used in marine environments HOWEVER austentic s/s in general suffer from a particular type of corrosion called “stress corrosion cracking” in the presence of chlorides (including salt) and this limits the use of austentic grades in structural (eg stressed) applications where that sort of corrosion will occur.

https://www.ssina.com/education/corrosion/chloride-stress-corrosion-cracking/

As per prior comment, it’s important to know the grade of stainless when using it for particular applications, to aid in this all the companies involved in the supply chain (eg stockists) need to be careful to have processes to keep the material labelled correctly at all times, it’s commonplace to insist on a “material certificate” traceable right back to the metal producer when buying stainless.
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Offline muskrat

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Re: Upgrade to Stainless Steel or Down?
« Reply #6 on: 28.10. 2020 08:58 »
Nice work Brian. I'm looking forward to doing the same.
I don't think there's too much stress on our 40hp weapons. The most stress is coming from the nut holding the handlebars.
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Online RichardL

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Re: Upgrade to Stainless Steel or Down?
« Reply #7 on: 28.10. 2020 11:33 »
The most stress is coming from the nut holding the handlebars.

Granted, but in my case, those holding the seat are also contenders.

Richard L.
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Online Butch (cb)

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Re: Upgrade to Stainless Steel or Down?
« Reply #8 on: 28.10. 2020 15:25 »
But some interesting points. I'm still running stainless (of unknown grade) retaining bolts on the brake callipers on a couple of my bikes ...
Warning - observations made by this member have a 93% unreliability rating.

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Offline worntorn

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Re: Upgrade to Stainless Steel or Down?
« Reply #9 on: 28.10. 2020 17:50 »
About 9 years ago I built an Egli style motorcycle frame in 304 stainless. Several people warned me that 304 stainless was -
1. Brittle and would fracture
2. Soft and it would flex so much as to affect handling.
3. Difficult to weld
4. Would be magnetic
5. Would corrode quickly.

I'm happy to report that none of the above turned out to be correct!

Glen

Online RichardL

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Re: Upgrade to Stainless Steel or Down?
« Reply #10 on: 28.10. 2020 18:33 »
Sure, but check again in 900 years.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline worntorn

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Re: Upgrade to Stainless Steel or Down?
« Reply #11 on: 29.10. 2020 03:49 »
This is true.
I sometimes wonder if it will even last 500 years. Oh well, I was warned:)



Glen

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Re: Upgrade to Stainless Steel or Down?
« Reply #12 on: 30.10. 2020 10:28 »
The last time I checked there were something like 3,000 grades of stainless steel so stainless is a bit generic without a number against it.
Stainless is not rustless
Rustless steels cover around another 100 or so grades .
So it is a case of the right grade of stainless.
I have a set of stainless pipers & mufflers on the A65L.
Never touched them and they ar still bright & shiny ( ish )
SR 500 Yammies came out with double walled stainless exhausts and you can actually watch them rust if not polished with the correct polish.
I know of 2 Road Rockets wearing stainless engine plates and they are doing fine .
I also know a person who bought cheap "stainless " head bolts and  blew a head gasket a weel till we finally convinced him to toss the pretty bolts.

Basicaly any steel with more than 0.5% Ni and 0.5% Cr is allowed to be called stainless .
So be a little careful when buying stainless .
It mus have a number attached to it.
Marine grade , avaition grade, military grade all bull shit terms .
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