Both PT and NPT are threads that connecting pipes. The internal and external threads are closely matched and can be divided into straight pipe and tapered pipe. NPT is an abbreviation of the National (American) Pipe Taper Thread, which is an American standard 60 ° tapered Pipe Thread used in North America. Pipe Thread, abbreviated as PT, is a Wyeth 55 ° sealed conical pipe thread used in Europe and commonwealth countries. The taper is 1:16 and commonly used in the water and gas Pipe industry.

Differences between metric and inch threads:

Metric thread, a type of standard thread, also known as metric thread, including normal thread (60° Angle); Trapezoidal thread (Angle 30°); Serrated thread (Angle 33°); Square Angle thread, etc. Specifications for inch threads are based on nominal size and number of threads per inch. For example, 1/4"-20,3/4"-10, 1"-8, 1/4"-20 means the nominal size 1/4, i.e. the large diameter is 6.35mm (25.4 divided by 4=6.35), 20 threads per inch, and so on.

Representation method: The metric thread is represented by the pitch, and the American and British thread is represented by the number of threads per inch (TPI).

Angle and threads form: Metric thread is 60° equilateral threads, American thread is 60° isosceles threads, British thread is 55° isosceles threads.

Unit: Metric thread is used in mm and American & British thread in inches;

In addition, the angle of other pipe thread is: ISO: metric thread 60 °; UN/API: uniform thread 60 °. TM pipe thread is 30°, SM needle thread and BC thread is also 60°, metric trapezoidal thread 30°, inch trapezoidal thread 29°.

NPT pipe threads size

Nominal diameter refers to the pipe diameter connected and the thread diameter is larger than the nominal diameter. 1/4, 1/2, and 1/8 are nominal diameters of inch threads.