[AT] Russian Metric uses BSPP was Thought to ponder

[James Peck]

Some of these fittings connect JIS Japanese Industrial Standard thread to BSP.

https://www.parker.com/literature/Tube%20Fittings%20Division/JIS_Fittings.pdf


For industrial equipment hydraulics I have used NPT pipe, steel tubing with a variety of fittings including O ring face seal, steel pipe with welded on flange fittings, and hose with a variety of fitting. I also have never seen metric pipe with tapered threads including BSPT.

https://www.mainmanufacturing.com/

[Bradford] John's experience is the same as mine. All the European wine equipment are metric, DIN, and IEC components but all the pneumatic and water fittings are usually plain ol' NPT. I initially expected 'metric' pipe. No such animal.
An exception are DIN fittings which are in MM. But those same DIN ends and nuts were used on inch size stainless sanitary tube. BSP is the PITA of the lot. One Italian company, a DE filter, used 80 DIN (3") non-taper ball valves with BST. From the factory the threads are wrapped with what looks like oakum and those suckers are tight. There's something from the dark ages. Perpetually difficult to get to seal and trying to orient the valve handle in a useful place was difficult at best. Solution? Cut the straight threads off and weld on I-Line fittings, which 99% of hoses and fittings are in a winery. That or TC. Then a valve can be replaced in one minute. 

[ John Hall] I've got 30 years in a machine shop and have yet to see a metric pipe thread--because it doesn't exist to my knowledge. We do a lot of German and Japanese work, it is always British pipe thread, either tapered or straight.
The whole planet seems to scream at the US to go metric, but they haven't developed a metric pipe thread. Yet all "normal" threads are 60 degree V thread form, but the British pipe are 55 degree. 
Furthermore, it depends on what country is building the piece of equipment as to the actual designation of the thread on the print--Trust me, no blue print ever made it so simple as to say "British pipe thread". There are 3 or 4 accepted/common designations for British pipe threads.  It is a mess of a system to say the least.