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  1. #1
    Eugbug's Avatar
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    Bolt Sizes - Imperial and Metric

    I am writing a hub on hubpages.com and I want to get my facts straight before posting them. As regards bolt sizes, in general is it correct that American engines use imperial size fasteners, British engines are metric and Japanese engines are also metric?

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    Re: Bolt Sizes - Imperial and Metric

    Quote Originally Posted by Eugbug View Post
    I am writing a hub on hubpages.com and I want to get my facts straight before posting them. As regards bolt sizes, in general is it correct that American engines use imperial size fasteners, British engines are metric and Japanese engines are also metric?
    That is the way I under stand it. Your metric system is so much easier then ours but I have been using inch system for so many years I don't like the metric system. I believe our fasteners are called imperial sizes but that word just isn't used over on this side of the pond very often, we use the word inch??

  4. #3

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    Re: Bolt Sizes - Imperial and Metric

    We are slowly getting away from inch size, SAE (Society of Automotive Engineers) ...

    With most everything very much a global trade now, we are gradually getting into the world standard.
    We are at a big disadvantage... Have to keep both SAE & Metric wrenches and hardware...
    It will eventually become metric. KennyV

  5. #4
    Eugbug's Avatar
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    Re: Bolt Sizes - Imperial and Metric

    Quote Originally Posted by reynoldston View Post
    That is the way I under stand it. Your metric system is so much easier then ours but I have been using inch system for so many years I don't like the metric system. I believe our fasteners are called imperial sizes but that word just isn't used over on this side of the pond very often, we use the word inch??
    Yes, I think the U.S. system is technically described as the "U.S. customary system" and some measurements are different from imperial. For instance the imperial gallon and U.S. gallon are different.

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    Re: Bolt Sizes - Imperial and Metric

    There are other variations as well. You will also run into Japanese fine thread quite often (same metric sizes, but different thread pitch). I've never seen SAE on a foreign engine, but very frequently see metric on 'american' stuff.

    Oh - there is also whitworth fasteners used on older british stuff. You need a whole new set of tools for those...

  7. #6

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    Re: Bolt Sizes - Imperial and Metric

    Quote Originally Posted by Eugbug View Post
    I am writing a hub on hubpages.com and I want to get my facts straight before posting them. As regards bolt sizes, in general is it correct that American engines use imperial size fasteners, British engines are metric and Japanese engines are also metric?
    That's how it was 30-40 years ago. Now they're all metric. It's getting hard to find inch size fasteners in most hardware stores unless you want stainless steel. If I want inch sizes I now have to go to a specialty store or TSC.

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    Re: Bolt Sizes - Imperial and Metric

    Oh - there is also whitworth fasteners used on older british stuff. You need a whole new set of tools for those...
    That was a running joke in the movie Cars 2 -- a must-see for all motor heads.
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  9. #8

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    Re: Bolt Sizes - Imperial and Metric

    Yeah, and the Brits specified their bolt sizes by the hex head size, i.e. wrench (sorry, spanner size) not the body diameter.

  10. #9
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    Re: Bolt Sizes - Imperial and Metric

    Quote Originally Posted by oldyellr View Post
    Yeah, and the Brits specified their bolt sizes by the hex head size, i.e. wrench (sorry, spanner size) not the body diameter.
    We measure our bolt size different to our spanner/socket size.
    We measure a 10mm socket size but bolt is a M6, a 13mm socket but bolt M8 and so on.
    It the same way as imperial do it. A 1/2 socket is a 5/16 bolt and so on.
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    Re: Bolt Sizes - Imperial and Metric

    Quote Originally Posted by pugaltitude View Post
    We measure our bolt size different to our spanner/socket size.
    We measure a 10mm socket size but bolt is a M6, a 13mm socket but bolt M8 and so on.
    It the same way as imperial do it. A 1/2 socket is a 5/16 bolt and so on.
    Pug, you're probably not very old, under 60, so you may not remember the Whitworth and BA stuff. I'm speaking about what I remember from over there from the 1950s when I lived there.

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