Tutaj jest fajnie opisane:
https://w5.siemens.com/italy/web/IC/bt/ ... ALVOLE.pdf
Tu można różnice m/ Rp a G poczytać:
http://www.ring-plug-thread-gages.com/ti-bs-Rp-vs-G.htm
i wrzutka z poradnika mechanika w wersji ogólnoświatowej:


Czyli krótko mówiąc:G/R/RP - WHITWORTH THREAD (BSPP/BSPT)
G = BSPP ISO 228 (DIN 259)
R/Rp/Rc = BSPT ISO 7 (DIN 2999 replaced by EN10226)
G/R/RP - WHITWORTH THREAD (BSPP/BSPT)
The most common types of whitworth thread are:
•
BSPP (G) – British Standard Pipe Parallel
•
BSPT (R/Rp) – British Standard Tapered Pipe, for pipes and tapered thread.
An appropriate sealing compound can be used in the thread to ensure a leak-proof joint.