British Standard Pipe Parallel
Popular couplings have British Standard Pipe (BSP)
threads, also known as Whitworth threads. These can
be parallel threads (BSPP) with a 30° inverted flare or
tapered threads (BSPT), with a 30° inverted flare. Port
connections are usually made with BSPP threads and
a soft metal cutting ring for sealing.
The BSPP (parallel) male will mate with a BSPOR
(parallel) female or a female port.
The BSPP male has straight threads and a 30° seat.
The BSPOR female has straight threads, a 30° seat,
and O-ring. The female port has straight threads and
a spotface. The seal on the port is made with an O-ring
or soft metal washer on the male.
The BSPP (parallel) connector is similar to, but not
interchangeable with, the NPSM connector. The thread
pitch is different in most sizes, and the thread angle is
55° instead of the 60° angle found on NPSM threads