A question about bolts.
 

We have a huge pool of knowledge on this forum which I would like to tap.

I've read numerous posts that the bolts we should use should be at least 8.8.

What exactly does 8.8 mean?
Whats the difference between 8.8 and 10.2?
How is this difference achieved?
Is any hardening simply case hardening or right through?
Lastly is there a table available with the information on the different applications?

Regards
Johan

Hi, Its not about hardness its tensile strenghth 10.2 is stronger than 8.8.
The way you get a higher tensile strength is by using a higher grade steel.
Dont think about them being hard think about them being tough/strong
They arent case hardened they should be the same all the way through.
There are tables for shear strengths of such items but i really wouldnt worry too much about that as long as the bolts are 8.8 grade or better and the correct size they will be fine.
The bolts should have the grade on the head of the bolt if not they could be any old rubbish.
Ray:)

This PDF has the information. In the UK we use ISO grades (page 3)

bolt guide

Cheers

Chris :)

Thanks gent's. Chris that table is pretty much what I was after, thanks.