Tapered thread for American pipes

ANSI / ASME B1.20.1 American-made national pipe tapered thread (NPT) is an acute angular shape with a 60° shank angle and is distributed in 1/16 of the taper on the conical tube. Although The taper of ISO R(PT) pipe tapered thread is also 1/16, but because the asan angle is 55°, it cannot be used with NPT thread.

* Base length: Since the thread diameter on the cone surface will change with position, an imaginary base plane is defined as a reference for the major diameter, middle diameter, and minor diameter. The distance between this surface and the external thread end face is called Datum length.