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Bolt Grades


brumster
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Just looking at the bolts supplied with my harnesses, they are non-metric so are marked Grade 5. This is the equivalent of an 8.8 bolt. The IVA documentation states that seat belt bolts should a minimum grade of 8.8 but does not reference the non-metric grading/markings, only the metric.

 

So if I present with non-metric marked bolts, will the IVA fail, even though the bolts are at an equivalent grade? ie. *must* markings be in metric only?

 

Thankfully it's only the seat belt bolts; everything else is metric. Can you even get UNF (I assume they're UNF?) bolts with a metric grading on them?! Don't think I've ever seen them?

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For a definitive answer, you will have to call your local IVA station, & speak to

the guy who will test your car, if the IVA docs are that unhelpful.

No guarantee that different testers wont "interpret" the regs differently.

Mine passed SVA with UNF bolts marked with an S.

IVA may be different.

 

Just found this... in the IVA manual, seat belt anchorage section

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/354071/M1_IVA_inspection_manual.pdf

 

Bolts used in structural areas should be of grade 8.8 or better. Such bolts will be marked 8.8 or 12.9 on the hexagonal head, however, cap-head bolts or 7/16" ( 11mm ) UNF seat belt anchorage bolts (with an anodised finish) not marked in this way may normally be considered to be of equivalent strength. Bolts should be M8 or larger.

 

HTH Bob

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Hi Dan, is your "grade 5 " marking a BIG "5 " if so that is an "S" which all (?) seat belt bolts carry. Seat belt bolts have always (?) been 7/16" UNF --- you may be able to fit an M12 bolt marked 8.8 if you're not happy with bolts supplied. ( believe IVA manual states to use M8 bolts or greater.)

 

 

Tother Bob types quicker.

Edited by florin metal works
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Cool, ok, I think we're fine then... it's amusing that the regulations in section 12 state if they're not marked metric, then just consider them an equivalent strength :D great bit of "handwavium" there!

 

I think with the 3-line (Grade 5) marking on the bolts it should be easy to convince the IVA guy that the bolts are strong enough, so I'll stop worrying. It was really a question of whether testers "apply reason" or "stick to the letter of the law" but, having now seen that later half of the paragraph you mention Bob, I can just play the "not marked in this way" card if the guy wants to be pedantic about it ;)

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Hi Dan, is your "grade 5 " marking a BIG "5 " if so that is an "S" which all (?) seat belt bolts carry. Seat belt bolts have always (?) been 7/16" UNF --- you may be able to fit an M12 bolt marked 8.8 if you're not happy with bolts supplied. ( believe IVA manual states to use M8 bolts or greater.)

 

 

Tother Bob types quicker.

 

Yup, I know what you're saying - the bolts are properly marked with the 3 lines to indicate grade 5 (and a 'WT' which I guess is the manufacturer code), they were provided with the harnesses so I've every confidence they're safe and correctly graded.

Edited by brumster
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If you are using the supplied bolts there should be no problem unless the harness manufacturer like to sell illegal gear ! mick

 

in theory yes but only takes one person to look for a fast buck or think any old bolt will do ;)

 

 

What is confusing is that i have heard people say that seat belt bolt should be 11mm (i think the unf equivalent) minimum but as above 'Bolts should be M8 or larger.'. For SVA i used 10mm 8.8 bolts passed without question. Made sure they had a smooth shank as well. Having 4 point fixings will put less strain on either way than a 3 point.

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I took a chart with me to the IVA, ( can find a few on the internet) that showed the strengths of the bolts, just in case I was question with regard to this. However, it was never questioned.

 

Nige

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Guest 2b cruising

IVA examiners come across this subject all the time.

They are mostly aware of different bolt grades.

I would imagine no problems would be met by you when it comes to testing time.

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I think it may have been Ian who sent me this useful link last year:

http://www.hi-tensilebolt.com.au/Head%20Markings.html

 

This shows the Imperial, Metric and Stainless markings with their tensile strengths, I am afraid my examiner at Derby did not recognise the imperial markings so it was one of my failure points.

 

I replaced the UNF bolts with metric 8.8 and all was fine on the re-test, even though the replacement bolts were actually a slightly lower strength!

 

Make sure the bolts you use actually have the 8,8 or 10.9 markings on the head, as not all bolts you buy are marked.

 

The other thing my tester did not like was the exposed triangular seat belt fixings, I had to make a "Sock" to cover them. Just a piece of folded plastic fabric over some foam did the trick.

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Guest mower man

A couple of points about this thread [ it may look like a rant but it's not justrying to help ] . Any bolt that is not grade marked should not be used for any thing load brg , Do not expect to get quality fixers from B+Q ,Halfords or the majority of suppliers on e bay unles they are actualy fixer suppliers .Most grades are available if you go to the correct outlets but some times have to be purchased in 10's or even 100's unless the guy on the trade counter is able to loose small amounts to samples , know exactly what grade , material, size and thread form you require and find your local nut and bolt[fixer] outlet most towns have one .Generaly they are much cheaper than even ebay and have wider ranges available . taking patterns is a good idea if you can .Personal visits and cash can work wonders !. I learnt this as agreen fresh faced fitter on the road and having to think on my feet to get jobs done . As said its not rant or apoke at any body but afew tricks I learnt [ and am still learning ] in 53 years bending spanners and knocking knuckles off mick :crazy:

Edited by mower man
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