NPSC Pipe Thread (USA)

The NPSC thread is an American pipe thread standard, which is part of the American National Standard Pipe Threads. This collection of thread standards describes various types of pipe threads for a wide range of applications. The abbreviation NPSC stands for National pipe straight–coupling or American National Standard Straight Pipe Thread for Couplings. This indicates that the NPSC thread is specifically intended for couplings, i.e., short pipe sections for connecting two longer pipes. Accordingly, the ANSI B 1.20.1-1983 (R1992) standard, which defines the NPSC thread, provides only for an internal pipe thread.

The NPSC thread has a flank angle of 60°. It matches the NPT thread in terms of thread profile angle and thread profile flattening but is cylindrical unlike the latter. A connecting piece with a cylindrical NPSC internal thread is screwed onto a tapered NPT external thread at the pipe end. This creates a connection that is not metal-sealing and must be supported with additional sealing material.

For the thread designation of the NPSC thread, each thread is assigned a numerical value in inches, followed by the pitch in threads per inch and the abbreviation NPSC. A common feature of all pipe threads is that the numerical value does not correspond to the external diameter. This is evident in the thread table entry for the 1″ – 11 1/2 NPSC thread, which actually has an external diameter of 1.293 inches or 32.848 mm. This characteristic dates back to the early days of thread standardization when pipes had thicker walls.

Therefore, it is advisable to take a close look at the thread table for the NPSC thread. There you will not only find the correct external diameter in inches and mm, but also the pitch in threads per inch and converted into a metric value. Additionally, we have listed the core hole diameter you will need for working with the NPSC thread. To find the right tools for the NPSC thread, follow the links in the table.