Where to find imperial nuts & bolts

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SimonA

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I need some imperial size nuts and bolts for securing a cleat back onto my boat (old bolts have corroded).

I tried some bolts from B&Q which claim to be 5/16" but are slightly too big (by a very small amount, they go in but won't turn).

Other than mail order, is there anywhere you can buy bolts in imperial sizes?
 
I take it these are fitting into threaded holes, otherwise why won't metric ones do.

If they do have to fit existing threads what threads are they. Imperial but Whitworth, BSF, UNC or UNF (18 22 18 24 tpi respectively for 5/16")

Seateach in Emsworth used to sell Whitworth as well as metric.
 
They are to fit into exisitng threaded holes in the base of the cleat.

I have no idea what the threads are, how do I tell the difference? Ideally I was after somewhere I could take the old bolts and get them to tell me what they are.
 
If there is enough thread on the old bolts you should be able to gauge the standard from that, or you could try local blacksmiths, agricultural engineers etc to find a match, or drill and tap to the next suitable metric size.
 
[ QUOTE ]
how do I tell the difference

[/ QUOTE ] Well i have thread gauges for measuring the thread pitch as well as a vernier and micrometer for measuring the diameter. Without the wherewith all to determine the thread the only thing you can do is try known threads until you find the right one.

Whitworth and UNC you will notice have the same pitch at 18 tpi the threads are a different shape though but for most/many purposes will be interchangeable.

If the fittings are British they will most likely be either Whit or BSF but if American UNC or UNF

If you have the patience and the eyesight you should be able to use an ordinary ruler to see if it is 18tpi or one of the finer ones

5/16" is very close to 8mm. You have eliminted the possibility that they are M8 I take it.
 
[ QUOTE ]
5/16" is very close to 8mm. You have eliminted the possibility that they are M8 I take it.

[/ QUOTE ]

M8 bolts will go in and turn about 2 or 3 times, then stop. They are just ever so slightly too big.
 
M8 is just a gnat's larger than 5/16. (0.3150" vs 0.3125") More likely the thread pitch mismatch that's the trouble.

I would have gone for 5/16" Whit as the most likely. You've really got to determine the thread pitch!
 
Look in Yellow pages for "BOLTS" we have a company local called Bapps, I think they are a national company. They will have imperial or will get them for you. They may have stainless.If you take a sample they will size it for you.
 
Re: Where to find imperial nuts & bolts

Depends what thread form. In my experience most fastener companies stock UNF but nothing else, certainly in stainless. They may claim to stock them, but when you ring up the usual response is 'Nah, mate, haven't seen any of them for years'. I obtained some stainless UNC and Whitworth fasteners from Bosun Supplies in the US (where of course, they still use proper sizes). It wasn't too expensive, either.
 
[ QUOTE ]
And thread angle

[/ QUOTE ] And the truncation of the basic triangle that forms the thread but I was keeping things to their simplest level.
 
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