Smiths Chronometric S433/1/L threads

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david.anderson
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Re: Smiths Chronometric S433/1/L threads

Postby david.anderson » Mon Jan 06, 2020 10:27 pm

There is a bit of different information regarding Chronometric speedo threads on the net. This thread on “Speedo Disassembly and Cleaning “ regarding the Vincent 5” speedo clearly states the dial is held on with unc screws and the needle is fixed with a 12ba screw (not applicable to the 3” speedo)
http://thevincent.com/vininst.htm
this thread however states the threads are all metric but a discontinued metric thread. M2 x .45 whereas m2 x .4 is the current standard. It also states the nuts on the back are quoted in some literature as Oba when they are actually 6mm metric.
https://www.vincentownersclub.co.uk/thr ... eter.2017/
Has anyone got anything definitive.
David

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Vincent.vanGinneke
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Re: Smiths Chronometric S433/1/L threads

Postby Vincent.vanGinneke » Mon Jan 06, 2020 11:11 pm

Tantalising ! I took out my thread gauge and measured a WD and civil chrono.
It sure does look like the threads are M6...
But I like the idea of running a 0BA die along it for complete Britishness :lol:

metric thread chronometric  (1).JPG
metric thread chronometric  (7).JPG

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Re: Smiths Chronometric S433/1/L threads

Postby john.whiting » Tue Jan 07, 2020 2:09 am

yes,I agree with 6mm metric......and a very good reason is that all the mountings were doubtless interchangeable with the Jaeger units,because the chronometric speedo is not British ,but French in origin......thats right,no britishness involved .

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T Batnes
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Re: Smiths Chronometric S433/1/L threads

Postby T Batnes » Tue Jan 07, 2020 8:17 am

And, it is a bit funny that the tpm (turns per mile) is about 1609 on most Smiths speedos, which happens to be about 1000 per kilometer...
Ariel W/NG '40 "Bitzer", Triumph Thruxton '04, IZH-49 '56, Tempo Standard 150 '54.

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Bob.Murphy
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Re: Smiths Chronometric S433/1/L threads

Postby Bob.Murphy » Tue Jan 07, 2020 9:54 am

david.anderson wrote:Bob
The substitution of 0ba and m6 is not a ” bodge” in a low torque situation. This substitution, along with using a bolt or nut with 1 or 2tpi difference has been taught in our TAFE colleges as suitable practice for low torque situations that are subject to vibration for over 50 years...….. David


So they recommend using a mis-matched thread as a 'shakeproof' fix . . interesting.

The crunch question for me is - can they be unscrewed and re-used or is this a 'one-time' fix ??

We've had the same issue with 1/4" BSF and 1/4" BSCY nuts & bolts. people think they are the same (and they can be forced to mate) but they are not - BSF having 55 deg and BSCY having 60 deg thread angles.

Personally, I'd go for thread-locker rather than a thread mis-match but I'm just an amateur.

Bob.
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH

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Re: Smiths Chronometric S433/1/L threads

Postby pappleton » Tue Jan 07, 2020 1:21 pm

http://velobanjogent.blogspot.com/2008/ ... nd_21.html
Sacre Bleu! And Smiths sounded so British too.
BR, Paul
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Re: Smiths Chronometric S433/1/L threads

Postby roger.fellows » Tue Jan 07, 2020 1:57 pm

Nice one Paul, I don't understand it - certainly at first reading.
A few typos and grammaticals, but fascinating.

I still think the 'metric' in the name is to do with measuring, whatever the units involved.

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Re: Smiths Chronometric S433/1/L threads

Postby john.whiting » Wed Jan 08, 2020 2:45 am

Jaeger were and are high end watchmakers ,with timepieces selling for enough to buy a fleet of Ariels.....If interested in the history of british Jaeger ,its found in the company website......Anyhoo ,seems the British Jaeger was French controlled until 1940,when Smiths bought them out at the direction of the War Office....The instruments were critical war supplies ,and not for motorbikes either. ..Smiths did already have a minority share.......no prewar chronometric is branded Smiths,because Smiths did not make them.

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Re: Smiths Chronometric S433/1/L threads

Postby JohnnyBeckett » Wed Jan 08, 2020 1:20 pm

hi i know after the war MG took over a french company and all the nut and bolts they made had metric size threads with imperial heads because to retool would cost to much so metric threads was used in the uk a long time ago so i would not be surprise to see them used on old patts


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