MkIII chain tensioner/ adjuster and BST BOLTS

L.A.B. · Aug 13, 2015

Rusty bucket said:
I bought some Whitworth wrenches a while back I see they use a different sizing method , maybe the bolt shaft? Who knows,

You only had to ask!

http://www.enginehistory.org/british_fasteners.shtml

Whitworth wrench sizes are another source of considerable confusion. With the more familiar UNF, UNC etc., the number stamped on the wrench or socket is the dimension of the hexagonal bolt head measured across the flats. Whitworth wrench sizes indicate the size of the bolt, i.e., a wrench required for a 1/4 BSW bolt will have "1/4W" stamped on it. The wrench required for the equivalent ¼ UNC has "7/16" stamped on it, this being the dimension across the flats of the hexagonal bolt-head. To further confuse things, Whitworth hexes are NOT the same size as the equivalent UNC/UNF -- they are larger. For this reason, it is imperative that a set of Whitworth wrenches are purchased before working on any antique British machinery – otherwise, expect rounded-off hexes and busted knuckles, trademarks of the careless craftsman.

However, I would hasten to point out that certain fasteners such as the cylinder head bolts and nuts have 1/4W (.525") sized hexagons although they are neither 1/4" diameter, nor are they actual "Whitworth" thread.

Rohan said:
Now, about that BST. Again, almost all the fasteners on the cycleparts on a Commando are UNF = american threads = american wrenches fit.

Rusty bucket said:
Thank you thank you thank you! Rohan! I didn't realize I could stroll into the hardware shop and buy my bolts!

But be aware there are also a few UNCs lurking about too-which is why I continue to stress (at least, to Rohan) that the "American threads" are Unified, and not just "UNF".

Rohan · Aug 13, 2015

Sometimes, in the interests of clarity and to avoid total confusion, its easier to just say ALL UNF threads, on the cycle parts.
When the questioner is all at sea, and still coming to terms with american threads on a british bike.
And since this thread is still running, I rest my case....

I will in future revert to almost all though...

Rohan · Aug 13, 2015

Rusty bucket said:
Thank you thank you thank you! Rohan! I didn't realize I could stroll into the hardware shop and buy my bolts!

No worries, pleased we could help !
It comes as a surprise to many to find that Nortons started using american fasteners on the cycle parts,
but its stil a bit of a mystery that they only used a few in the engine.
Just part of the mystique of the Norton ?

L.A.B. · Aug 14, 2015

Rohan said:
Sometimes, in the interests of clarity and to avoid total confusion, its easier to just say ALL UNF threads, on the cycle parts.
When the questioner is all at sea, and still coming to terms with american threads on a british bike.

Well, that's got to be one of the most ridiculous things I've ever heard! :roll: Sounds more like you're trying to dig yourself out of a hole as the person "all at sea" here, would seem to be you!

MkIII chain tensioner/ adjuster and BST BOLTS

L.A.B.

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Rohan

Rohan

L.A.B.

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