Help me with a Fidelity Research FR64 part

Parrotbee, Metric pitch is not measured in "threads per inch".  The inch is not a unit of distance in the metric system.  However, one inch = 25.4 mm.  The millimeter, etc, IS a unit of distance in metric. If you count 25 threads per inch, that would equate to one thread per mm, which is expressed as a (metric) pitch of 1.0.  In the metric system, THAT is a standard pitch, albeit a "fine" pitch for an M30 part. (Metric has "coarse" and "fine", much like SAE.). The platter retaining ring for my SP10 Mk3 is M18X1.0, for another example.

@lewm 

As I mentioned at the top of the thread (I think), I DO know a machinist who most likely would make this single nut for the OP, if he is given the correct specifications to work from. That is Colby Lamb in Oregon, USA. I can provide contact info, if desired.

What if the OP is not in USA like myself ?

 Colby made me a new threaded retaining ring for my SP10 MK3 platter; without that part it is impossible to fix the platter in place.

 I think the price one can pay for an important part of the $8k turntable is another story.

I couldn't find any machinist who can make even one small screw for my B-60, they are all laughing at me, maybe if i will order 100 screws they can deal with it. With such a small nut it can be the same. They don't want to bother at all, at least in my town. Not every one is ready to work with such a small individual orders for cheap custom parts. 

https://www.ebay.co.uk/itm/304-Stainless-Steel-Select-Size-M25-M48-Thin-Hex-Nuts-Right-Hand-Thread/2...

They have the M30x1.0

The first Japanese engineers are educated in Germany so, as
Lew assumed, use(d) metric system. The stubborn and arrogant English and Americans thought that the rest of the world will follow them with their inscrutable measuring system (grin).        

One can’t help wondering if those German engineers were the same ones Russia sent back after the war.