NPSL Pipe Thread (USA)
The NPSL thread is part of the American pipe thread family. Pipe thread standards for various applications are summarized under the name American National Standard Pipe Thread. The NPSL thread is specifically intended for locknuts. The abbreviation NPSL stands for National Pipe Straight–Locknut. In full, the thread is called American National Standard Straight Pipe Thread for Loose-fitting Mechanical Joints with Locknuts. "Loose-fitting" describes the fact that the NPSL thread allows some play, and "Locknut" is the English term for a locknut. The NPSL thread is standardized according to ANSI Standard B 1.20.1-1983 (R1992).
The NPSL thread is a cylindrical pipe thread with a 60° flank angle. A connection is made through the combination of a cylindrical external thread and a cylindrical internal thread, and it is not sealing.
The thread identification for the NPSL thread consists of a numerical value, the pitch in threads per inch, and the abbreviation NPSL. As with all pipe thread types, it's important to note that the numerical value in the thread designation does not indicate the external diameter. Thus, a 1″ - 11 1/2 NPSL thread does not have an external diameter of 1 inch, but rather 1.315 inches or 33.401 mm.
The correct external diameters for the NPSL thread can also be found in the thread table below, in inches and mm. Also listed is the pitch in threads per inch and converted into a metric value. If you want to cut an NPSL thread yourself, you can also read the core hole diameter from the thread table. For dies and taps for the NPSL thread, simply follow the links in our shop.