The National Pipe Straight Mechnical (NPSM) female fitting has a straight thread and an inverted 30° seat. The male fitting has a straight thread and a 30° internal chamfer. The seal takes place by compression of the seat on the chamfer. The threads hold the connection mechanically. A properly chamfered NPTF male will also seal with the NPSM female. Some fittings are also available in Type 316 Stainless Steel.
NPSM female pipe fittings swivel for installation only. If you are looking for live swivel joints, please click here.