What is an NPSM Fitting?
National Pipe Straight Mechanical Fittings
National pipe straight mechanical (NPSM) fittings are female swivel fittings with a straight thread and a 30° cone and form a mechanical seal when mated with NPTF male fittings. NPSM fittings were designed to eliminate hose stress from twisting during assembly and to reduce to number of hose fittings required. The swivel nut on NPSM fittings is permanently attached to the body, and mates with a male fitting that has a 30° chamfer. When the 30° cone and 30° chamfer are paired together, a metal-to-metal seal is formed.