NPS = National Pipe Straight (PARALLEL)
NPSM = National Pipe Straight Mechanical
Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60° included angle and have flat peaks and valleys. Straight Pipe Threads need a gasket or O-ring to create a seal. While NPT and NPS threads will engage, they do not seal properly with each other.
NPSM thread often used in the Female Pipe Swivel was designed with 60° flank angle. The NPSM female pipe swivel seats on a 30° seat (chamfer) and is visible down inside of the swivel nut. This swivel nut is permanently attached to the body and mates with a male pipe thread that has a 30° seat (chamfer) machined into the end of it. The threads bring both 30° seats (flare and chamfer) together creating a metal-to-metal seal. The 30° seat is a chamfer machined into the inside diameter of a male pipe thread and should not be confused with a relatively small deburr chamfer.
Please contact our sales team to get more details about our NPSM hydraulic adapters.