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maddox
Joined: 21 Dec 2006
Posts: 786
Location: Belgium
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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.
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Sun May 17, 2009 4:34 pm |
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