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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2018 at 22:39
The difference between A2 and A4 stainless is it's ability to withstand corrosion. A4 is normally specified in marine applicatins.

A2 and A4 does not refer to the tensile strength of the material.
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 09:07
Originally posted by Brian UK Brian UK wrote:

The difference between A2 and A4 stainless is it's ability to withstand corrosion. A4 is normally specified in marine applicatins.

A2 and A4 does not refer to the tensile strength of the material.


Quite so. The number following the A2 or A4 specification, ie 70 or 80, for example, denotes the tensile strength. Hence a bolt specified as being of A4 80 standard is a high tensile, highly corrosion resistant bolt. Simples
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 09:28
But leaves unanswered the question: What application requires "high tensile strength" ? Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobV7 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 10:09
I think you need to remember that maybe only a very few on this forum will have any recognised advanced technical qualifications! All design engineers will have at their disposal reams of S.A.E. data relating to which materials and fasteners are required to perform a specific purpose. I ain't got any of that and I seriously doubt if anyone else on here has. After all, this forum is probably composed of lads and lassies in a shed with a set of spanners and a lump of metal that they occasionally feel a strange urge to dismantle. You are asking the wrong people my dear chap, so get you to your local technical seat of learning for enlightenment!Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 11:02
I think you're selling it short Bob. Some people here know more about some things than I do, is my idea, or I wouldn't bother.

Simples, as well  Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 11:18
Well I admit I have no technical qualification in the tensile strength of bolts, however I do posess the ability to look it up.
Plenty of information around online provided you look at technical sites and not rely on the "accuracies" on facebook. (That should of course read Innacuracies).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobV7 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 11:53
I wasn't making a disparaging comment about forum members knowledge but some folk get paid good money to do that sort of stuff for a living, and if the rest of us don't fall into that group then we just are interested amateurs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Android Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2018 at 15:36
there are roughly three tensile grades of steel bolts generally used ...in laymans terms......
these numbers are usually impressed into the head of the fastener.
 
8.8 is your B&Q general hard ware store jobby
 
10.9 is tougher
 
12.9 is the dogs dodahs .....caliper bolts, high tensile Capheads with rolled threads and forged heads
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Griffic Quote  Post ReplyReply Direct Link To This Post Posted: 10 Oct 2018 at 22:44
Hello and welcome to the forum.
As an ex-metallurgist in the auto industry my suggestion on high tensile bolts is to look for the strength marking on the head of the bolt i.e 8.8, 10.9, 12.9 etc and replace it with the equivalent grade stainless bolt i.e. replace 8.8 with grade 80. It is not always wise to go for a higher grade assuming more tensile strength is better. A higher grade bolt will have greater tensile strength but will be less tough, ( more brittle.) Although a 8.8 bolt has a lower tensile strength (800 N/mm2) than a 12.9 bolt (1200 N/mm2) it’s impact strength at at 30 Joules is double that of a 12.9 bolt. Higher strength bolts  such as 12.9 grade are also more prone to suffer sudden catastrophic failure due to hydrogen embrittlement and are not used by some car manufacturers for this reason. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote George S Quote  Post ReplyReply Direct Link To This Post Posted: 10 Oct 2018 at 23:17
That is very interesting. Changing to higher strength is not always better 
Like buying high performance bike when your brain is only low performance. Nothing but trouble 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BobV7 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Oct 2018 at 10:40
Originally posted by Griffic Griffic wrote:

Hello and welcome to the forum.
As an ex-metallurgist in the auto industry my suggestion on high tensile bolts is to look for the strength marking on the head of the bolt i.e 8.8, 10.9, 12.9 etc and replace it with the equivalent grade stainless bolt i.e. replace 8.8 with grade 80. It is not always wise to go for a higher grade assuming more tensile strength is better. A higher grade bolt will have greater tensile strength but will be less tough, ( more brittle.) Although a 8.8 bolt has a lower tensile strength (800 N/mm2) than a 12.9 bolt (1200 N/mm2) it’s impact strength at at 30 Joules is double that of a 12.9 bolt. Higher strength bolts  such as 12.9 grade are also more prone to suffer sudden catastrophic failure due to hydrogen embrittlement and are not used by some car manufacturers for this reason. 

Now this is a bloke I would listen to as my neck could depend on me making the right choice when it comes to changing fasteners!Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 11 Oct 2018 at 11:30
And Dave P. had it right from the start. 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 11 Oct 2018 at 13:25
Thanks, JPC. It's nice to be right occasionally. Would you sign an affidavit to that effect and send it to my good lady?
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blunderbust Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 21:23
Hi and welcome, I like you have just purchased a V9 Bobber and I love it. I have 3 other bikes but love the style and how easy this bike is to ride around town. I have to admit I am in the process of changing a few bits, like the seat (MG Comfort), the back end (I hate the rear lights and the way that it sticks up), the mirrors, the end cans, and the colour. I do not like any of the colours or the sticker decals that it comes with so they are all going, the bike is stripped down just now and I am about to paint the front light casing, the tank, the side plates and the rear guard in an olive drab (the rest, frame engine etc are remaining as is). You mention the panniers, I also don't like the supplied ones so I have decided to knock up a couple of side mounted Military style webbing bags, they look really good using the purpose built Hepco and Becker mounting system. I hope to have the bike finished and back on the road at the beginning of next week, if I do I will post a couple of photo's.
Ride Safe.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote am2222 Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 23:09
hi    there     like you just bought a v9 in roamer mode bike looks great added givi screed and rear rack mg bar end mirrors   never had a guzzi before and needed something lighter than my Honda xl100 vara   only issue is suspension the std are crap so will look to upgrade    any idea whats best   Andy
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