Stainless steel grades

[roohairy]

Hi all,
Would appreciate some advice re. use of stainless steel fasteners! I know that 316 is commonly used as a marine grade stainless steel, but what fasteners are best? A2 / A4 commonly available, which is better or should I look for something else?

Thanks!

[Rogue Wave]

a4 unless sombody with a name beginning with J says different

[Jono]

...you know, what you really need to use is...

[Jonny Fuller]

As I understand it, A2 fasteners are manufactured using 304 grade SS, and A4 with 316 grade (the better marine/medical/food grade)

A2 tends to leave dark streaks down ya shiney bits when exposed to the elements, unless it's highly polished, which seems to stop that happening.

Hope this helps.

[Rogue Wave]

when I said somebody with a name begining with J i meant Johan from the Falcon factory

[TIM]

As far as I am aware, JF is right ...... Dont use anything less than 316 on you boat , in salt water...... I will break your heart

[Jono]

I hate to contradict FGT........ so I won't...

...'course if you seriously want to acheive better pitting resistance in sea water try getting ASTM spec bolts (American spec.) B8MLCuN or UNS32154's as the increase in Molybdenum to 6% gives much higher resistance than 316/A4's 2-3%....Now THAT'S what I call anorak knowledge..

[Jonny Fuller]

Jono, we need your knowledge (you Nobba) pray tel!

[Jonny Fuller]

So 304 is A2, and 316 is A4?

[Cookee]

Originally Posted by Jono

I hate to contradict FGT........ so I won't...

...'course if you seriously want to acheive better pitting resistance in sea water try getting ASTM spec bolts (American spec.) B8MLCuN or UNS32154's as the increase in Molybdenum to 6% gives much higher resistance than 316/A4's 2-3%....Now THAT'S what I call anorak knowledge..

Sounds great Jono - if you can tell me where to buy all this specialised stuff I would love to know - currently looking for some 1/2" UNF bolts for mounting engines in the strongest stainless stuff known to man!

Thanks -

[Rogue Wave]

Even i knew that and I haven't even got a Hardboat.

[Jono]

Originally Posted by Jonny Fuller

So 304 is A2, and 316 is A4?

Yup... .... Except in US where A2 and A4 are actually air hardened tool steels...and don't get me started on wire gauges...

[Jono]

Originally Posted by Cookee

Sounds great Jono - if you can tell me where to buy all this specialised stuff I would love to know - currently looking for some 1/2" UNF bolts for mounting engines in the strongest stainless stuff known to man!

Thanks -

Yeah, it does doesn't it? trouble is no one in this country carries stocks of "exotics" in the sizes that "boaties" find useful and everything's a trade-off. The most corrosion resistant doesn't have the highest tensile properties for instance.Best you can aim for if you require high strength and it's above the water line, if you need S/steel, is B8 class 2 (which is a 304 material heat treated and strain hardened to give good tensiles). Any good fastening supplier should be able to supply these, but there may be minimum order quantities.
I will look out some US contacts for you to try you may have luck there, they do tend to be more helpful with "nuisance" enquiries.
When we buy stuff like this it's generally special order, for larger sizes 60mm and above and it's a nightmare...

[roohairy]

Thankyou O knowledgeable ones! If you think getting US stuff in Europe is bad, try and get hold of 15mm compression fittings in the US!