NPT (National Pipe Thread) is the American standard compliant with ANSI B 1.20.1 standard.
NPT standards define the kind of thread and endurance obtained by contact and compression of the threaded flank with the female cone. NPT threading, usually used for carbon steel and stainless steel, can be used also for other materials such as brass, cast iron castings and plastic materials.
The standard norm has a variant – ANSI B1.20.3 – that defines the National Pipe Taper Fuel (NPTF), used in the petrochemical industry.
The NPT male thread can be referred to by using the acronyms MPT (Male Pipe Thread), MNPT or NPT(M). Instead, the female one can be referred to by the acronyms FPT (Female Pipe Thread), FNPT or NPT(F).
Commonly used sizes include: 1/8, ¼, 3/8, ½, ¾, 1, 1 ¼, 1 ½, and 2 in. These can be found on pipes and fittings used by most U.S. suppliers. Sizes less than 1/8 in. are sometimes used for compressed air, while sizes more than 2 in. are less common, mainly because other joining methods are more often employed with these larger sizes.
