What is Pipe Thread?
Pipe thread is a spiral ridge on the end of a pipe that enables pipes to be joined together. For male fittings, pipe thread appears on the outer diameter of the pipe; if female, the pipe thread appears on the inner diameter. By rotating a male pipe end into a female pipe thread, the two fittings become joined. Since male and female pipe thread must align successfully to form a connection, manufacturers follow pipe thread industry standards. The two main pipe thread standards are the National Pipe Thread (NPT), and the National Standard Free-Fitting Straight Mechanical Pipe Thread (NPSM). NPT is a tapered pipe thread that can make a close-fitting wet seal. NPSM is a straight pipe thread that only forms a mechanical seal and is not used for liquid applications. In the United States, garden hoses have their own pipe thread standard (GHT), as do fire hose couplings, which use the National Standard Thread (NST). When joining NPT tapered pipe thread to make a leak-proof seal, professionals r
