NATIONAL PIPE STRAIGHT MECHANICAL (NPSM)
The male and female threads of the NSPM connection are straight. In addition, the male has a 300 internal chamfer while the female has an inverted 300 seat. A mechanical connection is formed when the two halves are threaded together. The tapered seat forms a leak-resistant joint. NSPM connections find many applications in fluid power systems.
NB: A NPSM female can form a seal with a chamfered NPTF male.