NPTF Pipe Thread (USA)

The NPTF is an American pipe thread and part of the American National Standard Pipe Thread, which specifies pipe thread standards for many different applications. The abbreviation NPTF stands for National pipe taper–fuel and oil, or in the long form, Dryseal American Standard Taper Pipe Thread. The name of the NPTF thread already indicates that it was specifically designed for connections for transporting fuel, but it can also be used for numerous other applications. The NPTF thread is standardized according to ANSI B 1.20.3.

The NPTF thread is a tapered pipe thread with a taper of 1:16 and a flank angle of 60°. Unlike the NPT thread, the NPTF thread can be used for self-sealing connections without a sealant. The name component "Dryseal" indicates this. An NPTF external thread is either combined with an NPTF internal thread or with an NPSF internal thread.

The thread identification for the NPTF thread is derived from an inch value, the number of threads per inch, and the abbreviation NPTF. A possible thread designation is then, for example, 3/4″ – 14 NPTF. It is important to note that this numerical value does not correspond to the actual external diameter. With pipe threads, there is always the issue that due to historical pipe dimensions, a 1″ size corresponds more to an external diameter of about 33 mm, not 25.4 mm as one might expect.

The thread table for the NPTF thread includes twelve entries from 1/16″ – 27 NPTF up to 4″ – 8 NPTF. The table provides the exact values for the external diameter in inches and mm, as well as the pitch in threads per inch or mm. Also indicated is the core hole diameter at the thin pipe end. For NPTF dies or taps, please follow the links in the table.