Here is some metric bolt info:
http://euler9.tripod.com/bolt-database/22.html

So I asked for a high tensile bolt @ the local bolt shop and was sold a bolt with the 8.8 marking.

Is this the standard high tensile bolt in Australia? Can I get harder ones (8.8+) easy locally? Anyone know, thanks.

O yeah there's a reason I'm asking, I bent the 8.8 M10.


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havent seen anything over that at coventry myself, but you can get stainless ones here

https://www.bolt.com.au/index.php?cPath=1010_1588_1617_1618_1620

those 8.8 ones i think are a bit crappy. they always bent even when they where countersunk. now the heads just break off the stainless ones

maybe youd be best of buying pre-hardened shaft and lathing some slots for a circlip on either end or use a shaft collar etc
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An 8.8 bolt is standard industrial grade.

The cheapest bolts in a DIY can be as crappy as 4.6

For them who don't know the numbers.

Steel bolts carry the first number for the ultimate tensile strength *100 Newton mm²
The second number is the max load without damage in 10% .8 means 80% of the ultimate tensile strength.

For a 4.6 bolt that means 400 N mm² before breaking, and above 240 N mm² load it will elongate.

An 8.8 bolt is a lot stronger.
800 N mm² breaking load and 640 N mm² as max work load.

The strongest steel bolt I know of, and used, is the 12.95 .
1200 N mm² ultimate strength and 1140 N mm² max workload.

But, the higher the grade of bolt, the more stiff, and brittle they become.

Stainless steel bolts ain't stronger than the 8.8's, but are a bit less brittle.
Personal opinion
Don't use countersunk allen key bolts, as the small, shallow keyhole will become round in a hurry.

If you need stiffness in a bolt, you'll need a strong material and big diameter, or will have to manufactor something yourself.
I'm partialy to 7075 T6 rod reworked to seriously oversized bolts- with a hole trough to get rid of a bit of weight, and because pipe is stiffer for a given weight that rod.

Thanks Mario.

I'm liking the 7075 T6, i've been using 2011 T6. I'll price 7075 this week....
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Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.

With oversized in 7075 I mean replacing a 12mm bolt with a 22mm one-hole 10mm-.

you might want to look at how your using the bolt.
100mm long is a pretty long bolt and it seems bent over a nice radius, like the load was a long way from the support.
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Thx for the input. The bolt was just in a prototype, the design was not great but It was just to get a result. It was actually held on the middle 33% of the bolt and the start and end 33% of the bot are bent.

What you and Mario have suggested about design is all good and I agree, but I was more just interested in local supply of high tensile bolts info. Thanks.

Do you know what the hardest bolt locally is that you have seen?
_________________
Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Albert Einstein.

maybe something like the ones here
https://www.bolt.com.au/index.php?cPath=1010_1011_1977_1981
remember they become more brittle and stiff
they are 10.9

Anything higher you would need to talk to an engineering bolt shop.
Ones that deal with lots of engineering firms may be best.
10.9 should be common enough for a shop that sells to firms.
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Last edited by seanet1310 on Tue May 19, 2009 4:44 pm; edited 1 time in total

Localy,I can order 12.95 bolts, but only by box of 100 up to M6 and box of 50 up to M12. Higher than that will be negotiable.

Unfortunatly, localy for me is a bit far away for you.
But 10.9 isn't that uncommon or especialy expensive.

http://autospeed.com/cms/A_110592/article.html

pretty good info on bolts here
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http://www.youtube.com/user/HyzerGlen - Videoooozzz