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Metric bolt sizes


Juggalo

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Can someone help me out, I'm a bit confused on bolt sizes.

I always thought that an M10 bolt would have a 10mm head...for a 10mm spanner. M13 - 13mm head, etc..

So I want 17mm stainless bolts for my exhaust, but they don't do an M17.

 

:wacko:

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Not sure. Think I have a spare bolt..

So it has a 8.8mm thread (size stamped on the head) and a 17mm head. Still confused which M size that would be

The "8.8" has nothing to do with what size it is as it relates to the tensile strength of the bolt.

 

On bolt heads you can get all sorts of stampings on them including: a manufacturers mark, tensile strength, what grade they are ("A270" stainless steel for example) or various marks/symbols to indicate all of the above etc.

 

Link: https://www.google.co.uk/search?q=markings+on+a+bolt+head&rlz=1C2TEUA_enGB574GB574&biw=1366&bih=643&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjS_Z_spOLNAhXIBcAKHW6bCFMQsAQIIg#imgrc=_

 

 

 

 

 

UN0030_5231351147979.JPG

 

Although there can be some variants on the head size (spanner needed) depending on the country of origin.

More info: http://stainlessautomotivefastenings.co.uk/pdfs/HEXAGONHEADIDENTIFIER.pdf

 

:thumbs:

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Ah right ok, didn't realise that. So I'm looking at an M10 for a 17mm spanner. Cheers :)

Yep but as I mentioned there can be some difference on head size/spanner needed depending on the country of origin for the bolt. Hence why I put up the table picture & the link to another size table. ;)

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Ah right ok, didn't realise that. So I'm looking at an M10 for a 17mm spanner. Cheers :)

Yep but as I mentioned there can be some difference on head size/spanner needed depending on the country of origin for the bolt. Hence why I put up the table picture & the link to another size table. ;)

 

Uh :blush:

Think I'll find a fastener supplier rather than order offline. Better to be sure I guess.

They need to standardise this stuff.

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Uh :blush:

Think I'll find a fastener supplier rather than order offline. Better to be sure I guess.

They need to standardise this stuff.

I usually go to a local supplier called Phoenix as they're so cheap for decent stainless steel bolts/nuts/washers etc and as you say you can see exactly what you need so mistakes don't get made.

 

Screwfix do have bolts too btw and I'm sure there'll be a branch local to you. I bought a mixed set from them years ago similar to the one below...

Link: http://www.screwfix.com/p/mixed-nuts-bolts-washers-pack-a2-stainless-steel-500-pcs/10425#product_additional_details_container

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