Norton Atlas tach drive

drp

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The threads where the cable screws onto the tach drive on my Atlas are boggered up and I'd like to try salvaging it rather than buying a new drive.

Does anyone know what the thread size and pitch is?

Thanks

Dave
 
+1 also.

With the important note that there is nothing 'Whitworth' about it,
it is 26 tpi Cycle Thread.

Americans generally just don't seem to understand British thread systems,
and how there are a number of such systems that share ONLY the hex/nut sizes....
 
Rohan said:
With the important note that there is nothing 'Whitworth' about it,
it is 26 tpi Cycle Thread.
Click to expand...


Actually is 1/2 - 26 Whitworth thread.

Norton Atlas tach drive
 
Rohan said:
Americans generally just don't seem to understand British thread systems,
and how there are a number of such systems that share ONLY the hex/nut sizes....
Click to expand...

Absolutely... Let's call it "discovery learning" when I bought my first tap and die set. Very few true Whitworth uses on these bikes. Andy from Vintage British Cables helped me out with understanding cables and the fixing for them.

Scott
 
This is a voyage of discovery !

L.A.B. said:
Actually is 1/2 - 26 Whitworth thread.
Click to expand...

Where findeth ye that diagram. !?
And, who drew it - and is it likely to be accurately labelled ?

Now, everyone knows that that 1/2" Whitworth is 12 tpi, so what is one with 26 tpi called ?

Now2, my tacho drive is brass, so is it 26 tpi brass thread ??
Which could only be, very loosely. referred to as a 'whitworth' thread.
(whitworth must be one of the most loosely used technical terms in the english language.)
 
Rohan said:
Where findeth ye that diagram. !?
Click to expand...

In a Smiths catalogue.

Rohan said:
And, who drew it
Click to expand...

I don't know. Probably not Mr Smith.

Rohan said:
- and is it likely to be accurately labelled?
Click to expand...

As it's in a Smiths publication then I'd think there's a reasonably high chance it's accurate.


Rohan said:
Now2, my tacho drive is brass, so is it 26 tpi brass thread ??
Which could only be, very loosely. referred to as a 'whitworth' thread.
Click to expand...


'Brass' thread has a 'Whitworth' threadform. Note the term "WHIT. FORM" on the drawing. If it has a Whitworth threadform then it can't be 'Cycle' thread.

https://en.wikipedia.org/wiki/British_Standard_Brass
http://www.britishfasteners.com/threads/bsb.html
 
If it has 26 tpi, then its not part of the recognised Whitworth thread system !!

Now, I have a part set of Brass Thread taps and dies, 26 tpi.
55 degrees, not the 60 degrees of Cycle Thread.
Model steam engines, etc.
Although 1/2" is a bit bigger than usual.
Although maybe not for tacho drives.

I notice the speedo drive uses a different size thread.
What would that be. ?

BTW, I notice too than an Atlas tacho cable uses about exactly the same cable as a
prewar Norton speedo drive (off the front wheel). Same fittings, same length ?

PPS. Perhaps we should ask if UNF and UNC have the same 'thread form' ?
 
Rohan said:
If it has 26 tpi, then its not part of the recognised Whitworth thread system !!
Click to expand...

As already stated, it's Whitworth thread form.



Rohan said:
I notice the speedo drive uses a different size thread.
What would that be. ?
Click to expand...

Depends which "different size" you mean?



Rohan said:
PPS. Perhaps we should ask if UNF and UNC have the same 'thread form' ?
Click to expand...

And why would "we" need to ask that?

http://www.britishfasteners.com/threads/unf.html
UNF
Norton Atlas tach drive

http://www.britishfasteners.com/threads/unc.html
UNC
Norton Atlas tach drive
 
bad_friday said:
There seems to be a difference between 1/2" BRASS and 1/2" CEI
Click to expand...

There is.
'Brass' is 55-degree thread.
Norton Atlas tach drive


CEI/BSC or 'Cycle' is 60 degree.
Norton Atlas tach drive
 
Thanks to everyone who responded. Bought a die for $29 (1/2 - 26), chased the threads and I have successfully salvaged my Tach drive

Dave
 
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