Properties of fasteners

[DeeAitch]

If you are inerested in finding out more about the properties of fasteners then here is a good place to start.

For conventional fasteners look at section T15 . For bolts you will normally get either Grade 5.6 or 8.8. It will be marked on the head. I never use 5.6! (not on my car anyway)

High tensile is Grade 12.9, typically used for Socket cap screws. If in any doubt about what to use then this is what you should go for.

For Stainless look at section T28
Normally you will get these in A2(304)-70 or A4(316)-70 and this should be marked on the head. If it has no marking then you must assume it is either A2-50 or A4-50.

You will see that Stainless are significantly weaker than High tensile


Sy, Couldn't think of a good place to put this info so please move it if you have somewher better in mind

[John_W]

Dave,
Useful info. Thanks.
John

[ESM]

One point that you have to consider against 12.9 bolts is that they are generally more vulnerable to weakening through evironmental corrosion than lower strength bolts. The 10.9 grade often offers a good compromise between corrosion resistance and strength in applications where the bolt is exposed to the environment and salt in particular. In general if you are replacing bolts try to use ones with similar properties to the originals.

[DeeAitch]

The 10.9 grade often offers a good compromise between corrosion resistance and strength in applications where the bolt is exposed to the environment and salt in particular

Good point Alan. IIRC this is the grade chosen for the Willwood brake rotors?

And don't forget the copaslip!