What are the types of threads?

The most common threads in the 2 piece fittings are BSP type cylindrical threads, since the sealing is always done by means of a flat gasket.

How to differentiate between NPT and BSP threads?

The NPT thread is a conical type thread, with the pitch measured in inches and with its flanks at 60º. The BSP thread is a cylindrical thread, with the pitch measured in inches and its flanks at 55º. For optimum identification, it is advisable to use the corresponding gauges.

THREAD
BSP
BSPT
NPT

TYPE
Cylindrical
Conical
Conical

STEP
In inches
In inches
In inches

FLANKS ANGLE
55º
55º
60º