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Smiths speedo drive

Can someone tell me the thread size from the speedodrive connextion on the brake plate?

Re: Smiths speedo drive

The early type that screws into the brake plate ?

23/32" BSCy.

Re: Smiths speedo drive

Thanks Rik 👍 now looking for the tap

Re: Smiths speedo drive

Bram
Thanks Rik 👍 now looking for the tap
Are you looking for the fitting that Norton's used on their WD 16H / SWD Big 4 brake plates to accept the speedo drive unit?

Re: Smiths speedo drive

I have a damaged threet so need a tap to repair

Re: Smiths speedo drive

Bram
I have a damaged threet so need a tap to repair
Fair enough - it is just that I was sorting some stuff out in the garage and found I had a spare surplus to requirements.

Re: Smiths speedo drive

Rik
The early type that screws into the brake plate ?

23/32\" BSCy.
I have a look for this size bud can’t find it . Must I search on a different discription?

Re: Smiths speedo drive

I'm not sure that it exists, Bram. I think that you'll need to talk to a machinist.

Re: Smiths speedo drive

Rik,

Are you absolutely sure about 23/32? I have used an 11/16 x 26 BSCY tap for this, it works perfect. I have lend the tap already to someone else who used it for the same job with success. This is the kind of tap you buy and only need once.:grinning:

Regards,
Bastiaan

email (option): wdmotorcycles@gmail.com

Re: Smiths speedo drive

Bastiaan
Rik,

Are you absolutely sure about 23/32? I have used an 11/16 x 26 BSCY tap for this, it works perfect. I have lend the tap already to someone else who used it for the same job with success. This is the kind of tap you buy and only need once.:grinning:

Regards,
Bastiaan
And again , thanks Bastiaan 😄

Re: Smiths speedo drive

The drawings here are very hard to read, but they show .718" which is 23/32"

http://www.vintagebritishcables.net/Smiths-Gearbox-Motorcycle.php

It's confirmed in this article :-

https://www.voc.uk.com/net/docs/tl/speedodriveg-box.pdf

Re: Smiths speedo drive

I thought Rik must have got it wrong for once:smiling_imp: But it's clearly 23/32" (.718") and the guy in the Vincent article is right."The designer must have had a hangover that day"

But I guess an 11/16 tap which is 1/32" under size is enough usually to clean the threads up......Very interesting!! Ron

email (option): ronpier@talk21.com

Re: Smiths speedo drive

Ron Pier
I thought Rik must have got it wrong for once:smiling_imp: But it's clearly 23/32" (.718") and the guy in the Vincent article is right."The designer must have had a hangover that day"

But I guess an 11/16 tap which is 1/32" under size is enough usually to clean the threads up......Very interesting!! Ron
I will leth you know Ron if its fit.
Regards. Bram

Re: Smiths speedo drive

A machine shop would be able to make a tap of the correct size easily enough from some tool steel. That would serve OK just to clean up the threads...Ian:relaxed:

email (option): ian@wright52.plus.com

Re: Smiths speedo drive

Thank you Rick for the information. You are right about the thread size.

I have used a 11/16 x 26 BSCY tap and my speedo drive fitted perfectly.

Bastiaan

email (option): wdmotorcycles@gmail.com

Re: Smiths speedo drive

If you really do need this odd sized tap try Tracy Tools, they seem to be able to provide anything.

Re: Smiths speedo drive

I use 'Tracy Tools' sometimes, they're not too far from me......'The Tap and Die Company' in London are also very good and have a very extensive range..I've had a few 'oddities' from them over the years as well as the basic threads/sizes...Ian

email (option): ian@wright52.plus.com

Re: Smiths speedo drive

Neither of those companies have that size listed. Ron

email (option): ronpier@talk21.com

Re: Smiths speedo drive

['Neither of those companies have that size listed...']

Time to get to an Engineering shop probably, or find someone with a lathe and milling machine...This isn't a difficult problem to resolve if there's no tap available, as long as you have the thread specifications....Ian

email (option): ian@wright52.plus.com

Re: Smiths speedo drive


If you want a tap and/or die 11/16" BSCY 26TPI they are available. LPR Toolmakers in Victoria/ Australia have them listed, Aprica brand for $88.90 (Aus). probably a long way from you but someone else must sell them.

Link below should be for the item, they also sell on Ebay. They have most sizes in 26 and 20 TPI. I have some of them and the quality seems okay.


https://www.lprtoolmakers.com.au/1-2-to-1-26-tpi-2pc-tap-button-die-combo-hss-60-dec/

email (option): tknalder@iinet.net.au

Re: Smiths speedo drive

11/16 is not a problem Kim. The required size is 23/32". Ron

email (option): ronpier@talk21.com

Re: Smiths speedo drive

I have found that a tap can be made for a clean up of a thread by using a bolt of the correct diameter.
First, thread a nut onto the bolt all the way to the head.
Cut three or four grooves along the length of threads, using a dremel or similar tool to the style of a standard tap.
Then unscrew the nut, which clears the burrs from the edges, and dress them off with a small file.

For cleaning up a female thread, it works well.


A more permanent tap can be made by threading a length of silver steel and treating it to the same grooves etc. Then heat until cherry red and cool in an oil bath to harden.
It can just make these little jobs much easier and more satisfying if you can tackle them yourself.
Darren

Re: Smiths speedo drive

Darren, you'd first have to find a 23/32" BSC bolt and nut:laughing: Ron

email (option): ronpier@talk21.com

Re: Smiths speedo drive

The only male thread that I've ever seen in 23/32" is the monkey-metal drive box. You won't make much of a chaser out of that ! Usually they're sacrificial. Far more likely to be damaged than the female thread.

Re: Smiths speedo drive

Hello bram,
You can try with an threaded file.

email (option): jansenmarcel97@gmail.com

Re: Smiths speedo drive

😳 i am sorry Ron, i just assumed everyone has a lathe tucked away in the den.
Any bit of bar is a daft sized bolt just waiting to happen......

Darren

Re: Smiths speedo drive

Hoi Bram,

I will make a simple tap for you to borrow.
I do not have the proper dimameter silver steel so will make it from what is lying around.
It will not be used much anyway.

You know to find me,

Cheers,

Rob

email (option): wd16h@telfort.nl

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