Can anyone tell me what thread Parker uses (particularly on Duofolds) please ?
I seem to recall it is 36 tpi, and measures close enough to that with a thread gauge, but what thread form - UNC, Whitworth ....
Help would be appreciated.
Results of 'experiment' will be posted in due course.

Regards,
Ruaidhrí

I think Parker uses a non standardized special thread on their duofolds.
I found the external thread diameter being 10.8 mm (0.4252") when measuring on a new duofold.
Using a thread gauge I can confirm it is the 36 tpi you measured.
The 10.8mm is nearly 27/64" (10.72), being bigger as the standarized 3/8" & smaller as the standardized 7/16" threads.
The smaller 3/8" features 32 tpi in UNEF thread (Unified Extra fine) & the larger 7/16" features 28 tpi in UNEF thread.
This would imply the thread is a UNEF version.
I doubt however if you will find a thread making tap & die for such a special thread.
No big problem if you have a lathe off course !
Just thinking, the thread is very close to a Metrical M11 x 0.7 thread, also a rather exotic size. Could it be that Parker uses Metrical threads ?
Wishing you succes !

Thanks for the help.
I've also gotten a lot of information b/c on this.
Time to smash open the piggy bank & add a fourth lathe to my workshop
I'll update progress if and when.
Regards,
R