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Old 21 November 2005, 09:40   #1
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A2 or A4 stainless fasters

As some of you will know there are two grades of stainless steel fasters, A2 and A4, A4 being the best for Marine use but is more expensive and sometimes in more limited supply.

Can anyone advise if A2 is perfectly satisfactory for fitting out with or should i stick with A4 Stainless

I am thinking in general areas like the console etc
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Old 21 November 2005, 10:10   #2
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I am not a lover of Self tappers on GRP

It's a question of which one will corrode quickest and it's A2. The difference in the cost of fastenings would I imagine be in the region of thirty kwid and that's not worth lowering standards for on a Boat.

Screwfix do A4 nowadays and then there is always seascrew
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Old 21 November 2005, 10:12   #3
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Quote:
Originally Posted by Hugh Jardon
.....Can anyone advise if A2 is perfectly satisfactory for fitting out with or should i stick with A4 Stainless

I am thinking in general areas like the console etc
Depends on the job, but I use A2 for anything that is not permanently submerged and not too stressed Des
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Old 21 November 2005, 10:44   #4
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Quote:
Originally Posted by Rogue Wave
.......Screwfix do A4 nowadays........
Didnít realise this from now on itís A4 all the way Des
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Old 21 November 2005, 12:04   #5
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cheers for the gen


yes screwfix is the cheapest if have found so far which is excellent but their a4 range is a bit limited at the moment

a couple of other suppiers have come close and their range is better

has anyone found any good suppliers that are very cheap for A4 stainless? cheaper than Screwfix?
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Old 21 November 2005, 12:22   #6
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What is you are after? I work in a factory that produces food (for a little while longer anyway) everything we use here is food grade stainless steel, most of it A2 but I've been using on my boats etc for 14 years with no problems.
Let me know what you are looking for and I may be of some assistance. Got all sizes from M4 to M12 in varying lengths and types.
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Old 21 November 2005, 13:29   #7
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A2 will leave rust marks, always use A4 Chris.
Quote:
Originally Posted by Jizm
What is you are after? I work in a factory that produces food (for a little while longer anyway) everything we use here is food grade stainless steel, most of it A2 but I've been using on my boats etc for 14 years with no problems.
Let me know what you are looking for and I may be of some assistance. Got all sizes from M4 to M12 in varying lengths and types.
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Old 21 November 2005, 13:44   #8
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A2 will leave rust marks, always use A4 Chris.
Beware of cheap imitations! We have had stuff in the past, fasteners etc that claim to be A2 or even A4 but have rusted like buggery. Turned out to be a dodgy batch or cheap chinese stuff etc. Now we get all our stuff from a reputable supplier. Despite him being a bit more pricey than others, you know you are getting what you ask for!
I have seen rust marks around stainless bolts, but thankfully not on my RIB. Most of the fixings on mine are A2 and some are A4.
Hope this helps.
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Old 21 November 2005, 14:02   #9
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try http://www.a2a4.co.uk/
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Old 21 November 2005, 14:08   #10
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Quote:
Originally Posted by Jizm
Beware of cheap imitations! We have had stuff in the past, fasteners etc that claim to be A2 or even A4 but have rusted like buggery. Turned out to be a dodgy batch or cheap chinese stuff etc. Now we get all our stuff from a reputable supplier.
Were your fastners stamped on the head with the spec?

Very useful post from Jono here:
Quote:
Originally Posted by Jono
The designation A2/A4 is actually only part of the designation of a fastener. The important bit, in terms of strength is the second part, which is often left off. A "proper" code would be something like A2/50 or A4/80.
50 is lowest strength 80 is highest. They are in Newton/MM squared and the numbers represent 1/10 of their strength.

A4/80 is 316 (16/10/2) stainless with a tensile of 800 N/mm2

A4 is not a "better" grade than A2, it's just different and has different chemical properties. A4 is a 316 material, A2 is 304 type (or 302 if yer a yank..). 316 having added Molybdenum content and increased Nickel (hence more money..) which is good for corrosion resistance against certain substances such as chlorides. Hence the use in marine environments.

8.8 marked bolts have tensile of 800ish N/mm2
10.9 = 1040ish
12.0 = 1270ish

Hope that helps y'all out...
I have bolts form screwfix (and manufactured by these people: www.vibo.com) holding a vital component in the engine (trim-tilt assembly) and did a quick inspection yesteday - all OK and no signs of any discoloration at all.
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