What exactly makes aluminium an 'aerospace' grade? 7

[Harry.]

I know that aerospace grade means that they are more durable and lighter for Aerospace industries, but what exactly are aerospace bolts? Are they just made of stronger aluminium?

 

[kingnero]

What makes "Aerospace grade" fasteners =>
Probably the paperwork that they come with...

To be honest, I have no idea.

 

[mrfailure]

I generally consider an "aerospace" material to be one specified under the AMS (Aerospace Material Specification) issued by SAE International. AMS materials are not just aluminum; they can extend to any metal alloy as well as such things as solvents and fluids. AMS materials are usually called out to have a high quality, usually higher than equivalent materials called out under other specifications. Also note that old military MIL specs are now also governed under the Aerospace AMS specs. (I want to say that all MIL specs have transitioned to AMS specs, but I probably am wrong...)

 

[SnTMan]

Otherwise it's just marketing-speak.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[EdStainless]

None of the old MIL specs are being maintained, but a few still exist.
AMS (part of SAE) has taken all of them over. Well at least all that people wanted.

Aerospace like any high reliability service requires better documentation of the source of the material and how it was processed. In many cases there is special testing (either NDT or mechanical).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[TugboatEng]

Pedigree makes aerospace grade. Beyond that, some alloys such as 6061-T6, 7075, and 4130 may be advertised as being aerospace grade because they were developed for or extensively used in the aerospace industry. It's really just a gimmick.

 

[Harry.]

So are these 'aerospace' nuts:

https://www.accu.co.uk/en/hexagon-nuts/268690-HPN-M6-AL

because they are aluminium grade 7075?
I would have thought that they need to be certified for use in the aerospace industry or on an approved list?

 

[3DDave]

Those would mostly not be suitable in an aerospace application unless one did not care if the nut failed.

Why would you think otherwise?

 

[SWComposites]

1) aluminum threaded fasteners are rarely used in aerospace
2) at 0.17 cents each they are most likely not aerospace grade
3) “aerospace grade” generally means a material, part, etc is fabricated and purchased per engineering contolled specifications, either industry such as SAE or companny specs, and tested to certify compliance with the specs, and has been found to be suitable for aerospace structures.

 

[Harry.]

I see, I knew that Marine grade stainless steel usually refers to stainless steel 316, So I wondered if aerospace fasteners was a term that was used to refer to a certain grade of aluminium.
For example, Aerospace grade bolts are supposedly used on the roof of Tesla's Model S car. It apparently broke a testing machine that was pushing down on the roof with the equivalent of the weight of four cars. I guess its just a gimmick in this case, especially if threaded aluminium fasteners are not often used in the aerospace industry.
Thank you

 

[moon161]

It apparently broke a testing machine that was pushing down on the roof with the equivalent of the weight of four cars.

Tesla have some catching up to do then

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[mrfailure]

Honestly, I would not get hung up on the term "aerospace". Harry, the nut example you provided the link to never used that term. Instead, you need to make sure the material has sufficient properties for the application, regardless of specification. When I worked for an aerospace company, we specified a combination of material types including proprietary, AMS, ASME, ASTM, ISO, EN/DIN, etc.

 

[WKTaylor]

Aerospace grades of metallic materials have very specific manufacturing processes, in-depth testing/inspections for consistent/verifiable physical/mechanical/dimensional/etc properties... and most importantly... NDI, physical and mechanical testing, which leads to legal certifications [to specification(s)] for each production 'lot'. This ensures the purchased material actually meets requirements and is fully traceable back to OEM production. What You buy, based on material certifications, MUST be exactly what was expected, or better, IE: You pay more but expect to get what was paid for.

Similar systems are in-place for manufactured aircraft/aerospace grade hardware, parts, components, etc.

This 'over-arching system' ensures that all elements and properties of the raw material remains consistent and meet published design-performance data... with 'monotonous regularity'.

NOTE.
When a production lot of metallic material is 'good-enough' to be certified/traceable as 'aerospace grade', then the markings/certifications will reflect all aerospace standards it meets... and MAY also list any 'inferior specifications' [commercial, etc] that it will also meet/exceed without even further review. There is a distinct logic for this 'system', IE: why specifically make small production-runs of material that only meets inferior specifications, hence has limited applications/sales. OK, OK... I suppose 'large mill-runs' for non-critical commercial purposes might be the exception to this rule.

NOTE.
Aerospace materials-parts-components are used at aerospace 'stresses'... hence we paying for traceable 'consistency, performance and safety'. What is terrifying to aerospace engineers is the risk posed by uncertified... or worse... [criminally] counterfeit [bogus] materials-parts-components that have probability of causing catastrophic in-flight failure. The potential profit margins to be gained by criminals selling low-grade [cheep] materials-parts-components to the high standard of 'aerospace' is the huge attraction.

NOTE/variation to previous statement.
In So Cal where I grew-up, until the mid-1980s, aerospace companies used to sell uncertified surplus materials, parts and components [bolts, nuts, etc], and swept-up shop-refuse [dropped-stuff] 'by-the-pound'. My dad bought a lot of this 'stuff' ‘as is’ for use on his homebuilt airplane project. However, this 'stuff' was a cash-cow-bonanza for small aircraft maintainers/companies that used what they were buying ['dirt-cheap M-P-C'] on general aviation aircraft at their maintenance shops.... and charging ‘nominal’ prices for the M-P-C. When there were fatal accidents traced to uncertified/counterfeit M-P-C, congress/FAA put a halt to this 'cash-cow practice': the mechanic ‘who touched or inspected’ the M-P-C ‘last’ was to be held legally [criminally] liable for the use of that M-P-C. Most aerospace companies [slowly] developed procedures for ensuring that the surplus M-P-C was sold by-the-pound as scrap that was truly non-airworthy... crushed/shredded/cut/etc... in-order to avoid any future secondary liability. Obviously [sadly?], many mechanics/shops that were used to buying uncertified M-P-C ‘dirt-cheap’ [to cut corners], had to drastically change practices... or ‘go out of business’.


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

What makes stainless steel 'stainless'?
The researchers contributed the 'steel', while the 'stainless' was delivered by the marketing department.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[IFRs]

To me, aerospace grade is just light and strong.
To me, marine grade is just more resistant to water than comparable materials.
To me, both are colloquial terms with no real meaning or pedigree.

 

[WKTaylor]

IFRs...

So, a quick story...

A lubricant expert, I worked with once, remarked that they had to explain why 'common' grease was specially formulated for aircraft... why NOT use 'good quality' automotive grease?

'She' asked, simply, what is design-environment standard was for automotive grease in say Alaska? -65F +160F.

Then, 'she' asked what is the design-environment standard was for automotive grease in the desert southwest? -40F to +200F.

'She' went on to explain the grease used in commercial aircraft had to be functional, from -100F to +250F for delicate movements in flight control components… up to 350F [or higher]depending on exposure to adjacent heat sources... such as aircraft wheel-disc braking [even higher short term for composite disk rotors]. These operating parameters also had to include exposure to 0-to-100% humidity, sand/dust, exposure to various electrolytes and lightning and electrical pass-thru discharge, etc...

Aircraft operate over wider ranges of environments, stresses and weight constraints than any other vehicle... and attain that performance using lightest possible materials at the highest possible stresses... with bet-your-life reliability.

Just a small example... I wish You could see a training paper I wrote regarding JUST the environment my military aircraft is intended to operate in... even impressed me when I had it 'all-together' in one document.

"A mile of highway will take you a mile, a mile of runway will take you anywhere." ~Steve, Blogger from Ohio.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[IFRs]

WK -

I think you missed my point.

As an engineer I appreciate the qualities that make a particular alloy, grade, composition, etc particularly appropriate for specific applications.

I just think that the vague terms like "aerospace grade" or "military grade" or "marine grade" or "professional grade" may have originated with the general public being wowed with technology or in awe of what real experts / professionals can do, but the terms have been co-opted by corporations wanting to push their brand ( Ford and military grade aluminum for instance - what bullsh**t!! ). They mean nothing except a gut feeling or hype. They may as well be another color and are certainly no guarantee of pedigree, quality, specification, strength, appearance, longevity, suitability for service, etc. These terms are here to fool the public into spending more for the same thing or worse. I would certainly not have any faith that a "military grade" bolt was better for a lawn mower than a typical grade 8 machine screw just because it said "military grade" on the blister pack. It's like the word "tactical" on flashlights - the serrated edge around the lens makes it a weapon? Really?

Anyway, that's my feeling, feel free to disagree !!

 

[IRstuff]

Sorry, sounds like sour grapes because someone created a superlative that impinges on stuff we do to distinguish their product so that they could use something other than New! Improved! or even 9th generation i7!


TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[mrfailure]

IFRs, you are conflating marketing hype with a real thing. As I noted above, there are standards defined as falling under the SAE Aerospace Material Standards(AMS)that are a real thing - the majority of materials from a broad range of manufacturers that I test for certification fall under those standards. There are also Military Specifications (MIL-Specs), though most now are classified under the AMS specs.

 

[dgallup]

But unless you call out a MIL spec or an AMS spec, the ads claiming the use of "military grade aluminum" mean nothing.

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