taps and dies

[73stagman]

Yes Julian. UNF bolts (and UNC) have a mark on the head... a letter "S" this signifies a strength of 925 Nmm2 (Newton per mm2) apparently (I had to google for the number... just always been told they are high tensile but didnt know how high!)

Normal A2 (A2-70)Stainless steel have a tensile strength of 700Nmm2 or at best if you can find them A2-80 has a tensile stregnth of 800Nmm2
Normal metric bolts are marked 8.8 which have a tensile strength of 880nmm2 and socket head cap screws have are 12.9 grade... much stronger than all the above at 1290 Nmm2

An anorak I know sorry.....

[jleyton]

An anorak I know sorry.....

Absolutely no need to apologise - that's really useful.

It's not something I'd ever thought about before although, now you mention it, it does make sense. Methinks I'd better check the bolts in my car

Cheers

Julian

[new to this]

Yes he should be!

why do you need high tensile fittings for seat bolts ? its not a structual part of the car.

julian i get my stainless bolts from www.polished-stainless.com

dave

[Goldstar]

My thinking was that a weaker bolt might shear in an accident (god forbid) and with insurance companies being desperate not to pay out if the bolts were not of original spec in a safety area they would be bound to weasel out of paying up?

Paranoid maybe but that was my thinking

Paul

[Phil]

When I (foolishly) tried to put a kit car through a SVA test vosa did check the seat mounts had high tensile bolts fitted amongst other things that a new mondeo would have apparently failed

[73stagman]

The seat is a highly stressed area of the car. The seat mount is a structural part of the car. You become fitted to the seat when you strap your self to it with a seat belt and therefore you need to rely on the integrity of the total assembly!

Stainless steel bolts are fine for the cosmetic bits you fit to the car. But door hinges, Bonnet hinges, boot lids and all the retaining catches need to be the original specification of fixing. Some of them were designed that way..... I know some were just picked out of the parts bins... rear hub mounts etc. and some were even over engineered.
However you are the most important part of your car and you need to stay safe!

[wilf]

Yes - beware substituting with stainless unless you are 100% certain they are of sufficient tensile strength. The usual "dress up" stuff isn't strong enough for critical areas.

[73stagman]

I would have my doubts over stainless steel wheel nuts unless I can be convinced they are of a high tensile steel.
A comment from a retailer to convince me would be good as I want to buy some!