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Overdrive Selector Switch BAU1074A


RogerH

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Hi Folks,

this is an old puzzler. Does anybody know the origin of the switch or why the manufacturer used a non standard thread form

It is very close to 5/8" diameter and has 13tpi.    This does no exist anywhere as a standard thread form.

The nearest standard 5/8" is BSF at 14tpi - that would have been a good choice

People now use M16x2mm (12.tpi)    but that standard however did not exists pre WW2. 

 

The British car industry did not waste money on oddities so why choose an oddity of a thread when something so close (5/8BSF) could have done the job.

 

Roger

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I did see this and it struck a chord as I have just been hunting down the thread on an MX5 reverse switch/neutral switch, which initially seemed to be something very odd (though different from yours), as it was so coarse.

Mine tuned out "easy" as it is M14 x 2, though it's not a very commonly used thread size.  Could yours be M16 x 2?  Would be pretty close?  Odd choice for the British motor industry at the time.

 

Nick

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Hi Nick,

it is a conumdrumnium.  The thread is defo  5/6" x 13tpi. As mention M16 x 2mm is so so close at 12.7tpi.

When this switch was first created there was no organised metric thread system - a bit of a hotch potch.

 

Very odd - probably no longer a chance of an answer - it;s 90 years down the line.

 

Roeger

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