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Smiths Angled drive thread

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Smiths Angled drive thread

Post  woodenhead on Mon Jun 26, 2017 3:58 pm

Hi
I am trying to fit a Smiths angle drive gearbox into my rear brake plate but I have a problem the thread is damaged in the brake plate.
I am trying to work out what thread t is the gearbox thread measures up at 0.712 inches which is an odd size and conversion gives me 18mm.
Would they have been using Metric threads back in the early 50's. ?
Any suggestions would be appreciated.
Regards
Mike d.
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woodenhead

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Angled drive threads

Post  piston 197 on Mon Jun 26, 2017 4:26 pm

According to the Smiths catalogue:- ( engineering drawings)

they are 7/8" x 26TPI CEI where they screw into the brakeplate
and 1/2" x 26TPI CEI where the cable fits

Makes sense really to use a cycle thread on a cycle application ?

Very different to what you are measuring ?? has someone re-threaded you unit ?? because 7/8" is nearer to 22mm than 18mm ??, or are you measuring the hole in the brakeplate rather than the thread on the drive as the minor diameter of the thread will be about the figure you are giving ??

JH

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Speedo drive

Post  kerabo on Mon Jun 26, 2017 5:29 pm

I can't quiet understand what your measuring. Are you talking the wheel spindle thread or the thread where the speedo cable fits onto the drive.
Most of the spindles are 9/16" bscy

Regards Ken
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WRONG TRACK

Post  piston 197 on Mon Jun 26, 2017 5:36 pm

Ken, you are on the wrong track, the question was about the thread that is on the angled drive that screws into the brake plate on early FB's etc The wheel spindle has nothing to do with this,
The angled drive screws into the brake plate and a gear inside the brake drum turns the drive, NOT the type you are familiar with that surrounds the wheel spindle

JH
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Re: Smiths Angled drive thread

Post  kerabo on Mon Jun 26, 2017 5:49 pm

piston 197 wrote:Ken, you are on the wrong track, the question was about the thread that is on the angled drive that screws into the brake plate on early FB's etc The wheel spindle has nothing to do with this,
The angled drive screws into the brake plate and a gear inside the brake drum turns the drive, NOT the type you are familiar with that surrounds the wheel spindle

JH
Opps

Sorry before my time.
Ken
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Not a lot before your time

Post  piston 197 on Mon Jun 26, 2017 6:04 pm

Ken,
not before your time ! FB stopped using the angled drive around 1953, but Greeves and Cotton continued to use them until about 1968 in both the 1/2 width steel hubs and the full width British Hub Moto-ally hubs
JH
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Re: Smiths Angled drive thread

Post  woodenhead on Mon Jun 26, 2017 6:40 pm

Hi JH
I'm measuring the dia of the thread on the where it screws into the back plate, it's a James back plate that I got from you so I don't know what to think i'll do a bit mote measuring in the morning.
Regards
Mike d.
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Measuring

Post  piston 197 on Mon Jun 26, 2017 7:03 pm

I have another brake plate to hand and have measured the inside size of the threaded hole it measures .680" or 17.28mm , so no way is this the correct size for a 7/8" x 26 CEI thread ??
I can only assume the info in the Smiths catalogue is wrong ???
It would seem more likely to equate with a 3/4"

JH
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Re: Smiths Angled drive thread

Post  woodenhead on Tue Jun 27, 2017 10:46 am

Hi JH
Just measured mine Brake plate and it is .680" also the inside dia of the lock nut is /680".
Its difficult to decide which is worst the back plate or thee body both could do with cleaning up.
I don't think another brake plate would solve the problem i'll some rust remover on the brake plate and try and ease the body with a needle file.
Regards
Mike d.
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Re: Smiths Angled drive thread

Post  woodenhead on Tue Jun 27, 2017 1:43 pm

It no fits. After careful wok on the external thread with a triangular needle file and a toothbrush and some rust remover on the brake plate it now fits together.
Regards
Mike d.
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Thread

Post  john87 on Thu Jun 29, 2017 8:27 pm

Ok, so how does the thread compare in size to the thread on the lower end of your headstock spindle, as they are threaded 3/4 Bscy...

john..

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Re: Smiths Angled drive thread

Post  woodenhead on Fri Jun 30, 2017 6:10 pm

It's smaller it measures 18mm and Tracy Tools do a Tap and die 18mm dia by 1mm pitch tap and die (just about 26 TPI) but is it right I guess we will never know!
Mike d.
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Re: Smiths Angled drive thread

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