American Taper Pipe Threads

The thread shown in the NPT thread table is one of the American pipe thread types. Pipe threads are required, for example, in the sanitary sector and in air conditioning and heating technology to connect pipes, fittings and valves. The pipe thread according to the NPT thread table is one of several possible designs, all of which are defined and monitored by the American National Standards Institute (ANSI). The specifications in the NPT thread table correspond to the ANSI B 1.20.1 standard.

For pipe threads, a distinction is always made between conical and cylindrical and between sealing and non-sealing.NPT stands for National Pipe Taper, where "taper" is the English term for cone or taper. According to the NPT thread table, the thread is therefore a conical or tapered pipe thread that is not sealing in the thread. It has a flank angle of 60°. The conical shape of the NPT thread is defined by an angle of 1°47'.

As you can see from the NPT thread table, the thread designation is made up of the abbreviation NPT and a diameter in inches, which does not actually correspond to the nominal diameter of the thread. This is because the inches in the thread designation are based on historical pipe dimensions. These have changed over time, while the thread designation has remained the same. You can see this very clearly in the NPT thread table with the entry NPT 1". Instead of the 25.4 mm outer diameter that you would actually expect here, this thread size has an outer diameter of 33.23 mm.

To make it easier for you to get an overview of the American pipe threads, we have compiled further information in addition to the NPT thread table.You will also find an NPT thread table with all the dimensions for fittings and pipes that you need for your work with the NPT thread. We also explain the differences between the non-sealing NPT thread and the dry-sealing fine pipe thread NPTF in a graphic. And finally, in addition to the NPT thread table, we also provide you with an overview of all American pipe threads, which allows you to compare them based on important characteristics such as seal and shape.

Please note:
The Major Diameter of 1" Inch Pipe Thread is about 33 mm or 1,3 Inches (not 25,4 mm)!
Historically it had it's origin from the manufacture of steel pipes in the beginning of the 20th century. In that time the normal 1" Inch pipes with the internal diameter of 1" Inch had a outside diameter of about 1.3 Inches (33 mm).

D = outside-Ø of pipe
E1 = pitch-Ø at length L1
L1 = position of handtight engagement
L2 = usefull external thread

L3 = wrenching allowance
L4 = lenght of external thread
L5 = external thread with complete thread profile
V = incomplete thread produced by the chamfer of thread cutting tool

The difference between thread profile of NPT and NPTF threads is the width of flat of profile on the outside and minor diameter. NPTF thread has got an overlap of profiles of internal and external thread. By this method, drysealing property is achieved. Compared to the NPT, NPTF is one thread longer on L1 + L 3 and L2. NPT = non-sealing; NPTF = drysealing

NPTF is because of the overlap of profiles of internal and external thread drysealing.
By NPSF and NPSI gets a taper thread (NPTF) into a cylindrical internal thread. This effects a closing by covering the thread profiles to receive a drysealing fitting.