Problems Sourcing A4-70 fasteners 1

[Ibreakstuffdigitally]

We've recently had problems in sourcing A4-70 fasteners. These are typically hex or socket head cap screws of M5 to M24 sizes, and a variety of lengths.

Some fasteners come in marked A4, some marked 316... and some marked A4-70.

The first two can be easily recognized as unwelcome, but even the last of these can be problematic. Further digging has shown that in some cases, even these fasteners are often not actually tested in accordance with any standard spec (ISO 3506 is the one I'm somewhat familiar with)

Does anyone have any suggestions as to how to source commercial fasteners to 3506 (or an equivalent if such exists) which are manufactured with specified tests and in place, and actually head marked A4-70 as mandated by spec?

Yes I'm aware that 3506 does not require marking for small fasteners (M4 and smaller) and that for certain lengths, torque to failure tests may replace elongation tests.
We're fine with that...

We just want to be able to buy fasteners that actually are A4-70s

 

[drawoh]

Ibreakstuffdigitally,

The equivalent to austenitic stainless steel like 316 would be A2-70. A2-70 is easy to get here in Canada.

Why A4-70?

JHG

 

[Ibreakstuffdigitally]

The environment will be marine atmospheric service with some occasional green water impingement, but the problem isn't so much "ordering A4-70" so much as it is actually being shipped A4-70 which really does conform to an acceptable definition of what A4-70 is. We've found many vendors who will sell us "A4-70" fasters that would only comply with a very strained definition of A4-70.

Quite appart from being shipped fasteners marked A4 or 316, We've been shipped fasteners marked A4-70 which, when the fastener certs were examined, were found not to have been subjected to the mandated testing required under ISO 3506.

Finding a reliable source for small lots of A4-70 fasteners which do comply with ISO 3506, or alternately with ASTM F738M is really the problem.

I'd be concerned that "A2-70" would be as easy or easier to order, but that A2-70, as per ISO 3506 or ASTM F738M would be just as difficult to actually obtain for the same reasons.

Again, I am aware that 3506 does make different requirements on fasteners of shorter lengths or small diameters etc. But we seem to have serious trouble finding fasteners of many lengths that comply with the requirements, whatever they may be for that specific length.

It's getting to the point where we're considering dissalowing A4-70 fasteners for any structural application, and using something more expensive instead.

 

[TVP]

I have two suggestions. The first is to try a large, reputable distributor for these types of products. Fastenal (also a manufacturer) and Bossard are the two that I would start with, and make it clear that you want A4-70 according to ISO 3506-1 with the appropriate documentation.

My second suggestion is to review a list of domestic/North American producers of stainless cap screws, and determine if any of them would be interested in the quantity of parts you need. Chandler Products or one of the other members of the Elgin Fastener Group might be a good possibility. Here is a link where you can search by product, manufacturer, etc.

http://www.indfast.org/search/

http://www.bossard.com/index.cfm?app_page_id=3082,1

http://www.fastenal.com/web/home.ex

 

[Graybags]

I regulary use A4-70 fasteners for non pressure containing bolting in salt spray environment. We (in UK) order to BS6105 (superseded by BS EN ISO 3506).

A4 is 316 austenitic - 2-3% Moly
A2 is 304 stainless - no Moly

 

[Ibreakstuffdigitally]

Gray: This sounds like a pretty similar environment and pretty much the kind of thing we want to order. Do you typically order large lots?

A part of the problem we have is that we typically build very small, prototype sized runs, with small orders. Companies that can control paperwork are, at least in our experience so far, interested in charging 300 dollars per line item to supply it.

The total size of the order might be hundreds of fasteners, but that might be split over dozens of parts.

We're still looking but...

 

[EdStainless]

You may not get what you pay for but you never get more than you pay for.
So either pay $300 or order a few extra, do destructive testing on those, and PMI on the rest of the lot. In the end it will cost you the same.
Another good US source

http://www.grandeurfasteners.com/

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Plymouth Tube

 

[Ibreakstuffdigitally]

Fair enough, however, our orders are small... and it's beginning to look like the logic will be: If A4-70s are $300 per line item, or even $100 more, then for 80% of our orders, we'll be able to get bufab 8.8s for less. Size-availability and delivery issues notwithstanding...

Of course... they always are withstanding.

This has certainly given me an education on how different people will have very widely varying definitions of what A4-70 actually means.