That size is very unusual, Jim.

The standard ME thread is of Whitworth profile and the 3/16″ diameter has 40 tpi; not 30 or even 32.

3/16″ BSW is of 32tpi.

30tpi is not standard at all: it’s not even a Cycle Thread or something that was called “Continental Whitworth”.

Incidentally, in the early-1980s a working-party established a Metric range suitable for fine-scale model-engineering, and although the British Standards Institute could not adopt it fully, it did add recognise it as an adjunct series. Does anyone know what happened to it?

(There is an ISO Fine series but although the taps and dies are readily available, e.g.from Tracy Tools, finding fastenings or pipe-fittings etc. made to that standard is not so easy.)

On 6 August 2026 at 08:42 Michael Gilligan Said:

It is clear from this thread:

https://www.practicalmachinist.com/forum/threads/a-source-for-british-whitworth-threads-in-a-3-16-x-30-tpi-screws.221376/

that Roderick’s AI advisor was correct

There is a small picture there which is worth a thousand words.

.

For a bunch of engineers … I think the interesting topic debate should therefore be WHY did Herr Luger choose to use that thread ?

MichaelG.

All Roderick’s AI advisor did was to find and look at the above thread which has some very knowledgeable replies. Could Luger have been using British machinery? The British invested very heavily in Germany industry before WW1, so much so that there was a massive run on the London stock exchange at the start of the war. The stock exchange closed for a good few months.

JA

Don’t forget that during the second half of the 19th century Whitworth’s system was pretty much the only system.  In those days Britain supplied the world.  The metric screw system was only standardised in 1898.  So, it is not really surprising that Whitworth threads turn up on all sorts of continental machinery.

Rod

On 6 August 2026 at 12:18 JA Said:

1/4″ Whit thread still rules the camera world – the mounting thread for tripods etc. I believe the EU tried to change it so the Germany standards office came up with a new thread – M6,35 x 1,6 x 55degrees.

JA

 

Why doesn’t that surprise me, when was that? – 01 April maybe?