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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?

Eugbug said:

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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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??

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. :smile:KennyV

reynoldston said:

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??

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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.

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...

Eugbug said:

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?

Click to expand...

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.

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

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That was a running joke in the movie Cars 2 -- a must-see for all motor heads. :laughing:

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

oldyellr said:

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

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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.

pugaltitude said:

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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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.

oldyellr said:

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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You are right I am well under 60 :thumbsup: but I used to have an old witworth set.
Still get mowers from 30s coming for service.
You will remember then that if a brit has bought something with an engine on then its meant to last 100 years :laughing:
Old landrovers, British leyland and old jags etc are still about and nothing else will fit it.

A couple years ago I picked up my second Triumph motorcycle - a 60's Trophy 250 (my first is a newer Bonneville). When I started tinkering on it I was a little stumped by fastener sizes that none of my metric or SAE tools would fit. A coworker has an old Jaguar and filled me in on the Whitworth sizes and I found a decent old set on eBay.