A very useful comparison--
Thread Content
Standard British pipe threads, American pipe threads; Pipe thread standards: non-sealing cylindrical pipe threads, sealing tapered pipe threads, generally sealing tapered pipe threads; External threads, internal threads – external threads, internal threads, external threads, internal threads. GR (1987–1999), Rc, NP, TR1, R2 (after 2000); Old mechanical drawing standards, GZ; The correspondence between the pipe thread codes of the old mechanical drawing standards and those of the current standards. Note: Before 1987, sealing cylindrical internal threads (Rp and NPSC) were rarely used in China. Last edited by andrew on 2007-11-30 at 15:24
:handshake – a very useful comparison