classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: ramwing7 on October 09, 2021, 03:09:24 PM
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I have a 1963 Norton Electra.
One of the breaker point pillar stud bolts has broken off.
I've extracted the remains, refilled the hole, and ordered new studs.
Thing I need to know is the size tap I should use to rethread the hole.
Anybody know that?
Many thanks.
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Points assembly pillar bolts are usually 2BA but I can't find a part number for them so what is the diameter and TPI?
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He'll struggle to meaure the tpi of a BA thread with a conventional thread gauge..... However, meauring the major diameter (in mm) should give the BA size. 2BA would be 4.7mm and 1.234568 threads /mm. 3/16" BSW is a similar diameter but 24 tpi.
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I can't think they'd use a Whit thread here, but can't you check the remaining stud with a 2BA nut?
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Thanks.
My kanoodling got me to 5mm, so I must be in the ballpark.
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How different are these to Commando ones - which are 2BA
And a shade over an inch long - overall.
btw, a 5mm nut will thread onto these - as a rather loose fit.
(https://www.classicbikespares.com.au/wp-content/uploads/2016/09/061281-Norton-Commando-points-plate-mounting-screw.jpg)
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It may wind on, but I'd never describe it as any sort of "fit".
Rather like OBA and M6, slack as something very slack, although there have been claims of interchangeability by some... :-X
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BA is a metric-based thread system.
Only the English could take that and mangle it just enough to call their own !?
It may not be any sort of 'fit' at all, but the 5mm going on at all means you can test what it may be.
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Given that BA stands for "British Association" I take it that you really mean British rather than English? That said, and given that it was a thread based on metric units, it wasn't "mangled" from anything else.
One of the most useful of the small threadforms, and far better than the metric series or the dreadful Unified small sizes.
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Hmmmmmm ?
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Give over you two. We all know it's 2BA. It's British electrical, what else is it going to be?
I like the BA thread. It's a practical thread form that makes for a much sturdier screw than comparitive sizes in other formats. The 47.5 degree form gives you a greater core diameter than the common 55/60 degree forms used by metric, US and Whitworth. Its a format designed for fine work in small diameters and it does it well. Yes, it's day is mostly done because electronic instrumentation and the microchip has taken over much of the old mechanical instruments of yore that it was intended for but that doesn't alter it's effectiveness.
Having a background of nutters who played with this stuff before I was a twinkle in my father's eye I now have the family accumulation of BA, Whitworth and SAE taps, dies and some ISO metric God Wot. BA is by far the sanest for small stuff. Just don't get me started on small ISO Metric.
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I agree that BA is a very logical thread series. Its only drawback for me is that it can't (at least not with any facility) be screwcut in the lathe which is what I prefer for male threads.
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Treat yourself (if you haven't already got one) to a tailstock die holder if you need to cut a BA thread on a lathe. Life really is too short to screwcut a BA thread on a lathe though..
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Even better is to get yourself a coventry die head.
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Yeah, if you're made of money... ::)
Hardly justifiable for the use-it-now-and-again amateur.
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I agree that BA is a very logical thread series.
Given that it was largely metric based, yes. !
Smiths meanwhile swallowed their English (British ?) pride, and used all metric
on the chronometric speedos, for many a year.
But reverted to BA etc on the magnetic Smiths range.
Odd, given that they had all that metric machining capability ?
Nationalism is a strange disease ...
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Yeah, if you're made of money... ::)
Hardly justifiable for the use-it-now-and-again amateur.
Coventry die heads and dies do turn up for very little money, a few years ago I was given buckets full of new and sharpened die sets from a aerospace company. They had gone over to thread milling and the die sets were headed for the scrap bin.Luckily the owner is a friend and sent them my way.
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Smiths meanwhile swallowed their English (British ?) pride, and used all metric
on the chronometric speedos, for many a year.
But reverted to BA etc on the magnetic Smiths range.
Odd, given that they had all that metric machining capability ?
Nationalism is a strange disease ...
Given that the chrono was based on a French Jaeger design keeping the Metric dimensions and specs was likely down to laziness, but that said the French components used "French metric" threads which required conversion to ISO metric stuff in later years.
Seems like even the so-called "universal" metric standards were far from universal even as late as the 1960s.
Given the meltdown of the old industries in the mid 1960s, who can tell the reasons why the reversion to BA threads on the later crap mag speedos, but whatever the reason(s) claiming that some sort of nationalism was the root cause really is nothing short of bizarre....
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nothing short of bizarre....
But true.
Stranger things have happened at sea ...
Fashion in nuts-n-bolts comes and goes.
I've owned a car which had an all metric body and an all imperial engine/gearbox.
And a Commando, which had an all AF/UNF body (mostly) with an all (nearly) imperial engine .
Nationalism has produced some strange bedfellows, thats for sure. !
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I would put that down to lack of money to invest in new tooling etc rather than any sort of nationalism, but maybe we just have a different understanding of the meaning for the word....
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I agree not nationalism but I can't see how changing half the threads to UNF/UNC would save money......
The worst thing on the Commando was the back head stud which was 5/16" cycle. It was (and still is) a bugger to get at and a 5/16" UNF "almost" fits until it seizes up after a couple of turns.....
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Well, then you have to ask WHY all the (very) British thread standards emerged, when all the early motoring was done with French engines
- so would have been largely metric . (even if metric wasn't standardized until 1919.)
A bit like really early American cars started driving on the left, but then switched to the right.
These decisions appear on the face of it to be less than entirely logical ... ?
Oh, and an Swiss clockmakers threads used 47.5 degrees, so we can see where BA got that from.
Even if the rest of it was nearly metric, but not quite.
One wonders if patent specifications may come into it somehow ??
Yes that top head bolt on dommies and Commandos was a pain.
I've misplaced the ground down socket that fits, don't tell me I have to do another one.
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Well, then you have to ask WHY all the (very) British thread standards emerged, when all the early motoring was done with French engines
The thread and fastener standardisation started by that nice Mr Whitworth started lonnng before the era of of early French IC engines...
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But Whitworth was almost entirely unsuitable for IC engine use.
Apart from threading a few stray coarse threaded studs into aluminium.
And he only standardized a hodgepodge of things.
Clockmakers threads on the other hand go way way back.
Salisbury Cathedral think/claim this is 1386
https://en.wikipedia.org/wiki/Salisbury_Cathedral_clock#/media/File:Salisbury_Cathedral,_medieval_clock.JPG
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But Whitworth was almost entirely unsuitable for IC engine use.
Apart from threading a few stray coarse threaded studs into aluminium.
/quote]
You seem to be presuming the Whit threadform was the sum total of the man's life.
Have a read-
https://www.whitworthsociety.org/history.php?page=2
His greatest achievement was the concept and start of thread standardisation across the industrial world, and with the greatest respect to medieval Salisbury cathedral, their particular claim is rather a non-starter.
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I'm not denying that, at all.
But if you take a critical look at things, the English (British) seem to have a penchant for taking
others perfectly good thread systems, and 'developing' it into something they can label as their own. !
So we have BA, which is a adaption/mangling of a Swiss clockmakers metric thread, 47.5 degrees and all,
such that present day metric nuts are a (poor loose) fit.
An indication of how closely they copied it. ? But not copied it exactly ...
I thought you'd be more appreciative of that Salisbury Cathedral clock mechanism.
Even if Mr Whitworth played no part in it.
Engineering was alive and well, post the Roman era !
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I'd also add that in my modest collection of bikes, I think I've previously counted something like
16 different threading systems. This covers a few continents and a fair spread of years.
But thats a lot....
There is a good reason of course why plumbing and electrical and general threads should be different,
so that never the twain shall meet, but ...
A Norton Commando has 7 (or 8 )? of those.
One I can dismantle with a single 12mm spanner/wrench.
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But if you take a critical look at things, the English (British) seem to have a penchant for taking
others perfectly good thread systems, and 'developing' it into something they can label as their own. !
So we have BA, which is a adaption/mangling of a Swiss clockmakers metric thread, 47.5 degrees and all,
such that present day metric nuts are a (poor loose) fit.
An indication of how closely they copied it. ? But not copied it exactly ...
Took/adapted/developed/whatever....you seem to have some deeper narrative you want to post about.
Do the Wokies know about this alleged thread appropriation? I don't want some pink-haired harpies picking up on your posts and cancelling my BA thread selections.
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Just pointing out the facts of life
Which some obviously never consider
Somewhat akin to some folks will tell you that Harley Davidson invented the motorcycle.
And they mean it...
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Always disconcerting when someone says they're only "pointing out the facts", as most appreciate that those "facts" have a habit of alteration and alignment etc subject to the beliefs of the person stating them.
Strange claims that nationalism was the root cause of a reversion to BA threads in the mid-1960s being a perfect example.
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Make of it what you will.
You must be ENGLISH then ?
Perhaps we could also point out that Mr Garner et al spent 2 years converting
the 961 engine design from american measurements to metric ones.
How fashions change.
And look where that got them ...