The difference between NPT, PT, G and other metric threads

NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree tapered pipe thread and is used in North America. National standards can be found in GB/T12716.


PT is the abbreviation of Pipe Thread. It is a 55-degree sealed tapered pipe thread. It belongs to the Wyeth thread family and is mostly used in Europe and the Commonwealth of Nations. Commonly used in water and gas pipe industry, the taper is 1:16. National standards can be found in GB/T7306.

G is a 55-degree non-thread sealed pipe thread, which belongs to the Wyeth thread family. Marked as G stands for cylindrical thread. National standards can be found in GB/T7307.

In addition, the 1/4, 1/2, and 1/8 marks in the thread refer to the diameter of the thread size, and the unit is inches. Insiders usually use points to refer to the thread size, one inch equals 8 points, 1/4 inch equals 2 points, and so on.

G is the general name of pipe thread (Guan). The division of 55 and 60 degrees is functional, commonly known as pipe circle. That is, the thread is processed by a cylindrical surface.

ZG is commonly known as pipe cone, that is, the thread is processed by a conical surface. The general water pipe joints are like this, and the national standard is marked as Rc.

Metric threads are expressed in pitch, while American and British threads are expressed in the number of threads per inch. This is the biggest difference between them.

Metric thread is 60-degree equilateral profile, British thread is isosceles 55-degree profile, and American thread is 60-degree.

Metric threads use metric units, and American and British threads use imperial units.

Pipe threads are mainly used to connect pipelines. The internal and external threads are closely matched, and there are two types of straight pipes and tapered pipes. The nominal diameter refers to the diameter of the connected pipe, obviously the thread diameter is larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameters of inch threads, and the unit is inches.

Thread angle: metric and American threads are both 60 degrees, inch threads are 55 degrees, TM water pipe threads are 30 degrees, SM needle threading and BC threads are also 60 degrees, metric trapezoidal threads are 30 degrees, inch trapezoidal threads are 29 degrees, counter-shaped threads (TW29 degrees TR and TM30 degrees).

Ordinary thread: metric thread M; inch W; American UNC, UNE, UNEF

Pipe thread: British PS, PT, PF; American NPS, NPT, NPTF, NPSM

Tuyere thread: The outer diameter of CTV and TV 1/4-20 is 1A: 0.2367-0.2489 (6.012-6.322); 2A: 0.2408-0.2489 (6.116-6.322) 3A: 0.2419-0.2500 (6.1443-6.350).

Inch thread: According to the nominal size and the number of teeth per inch to make specifications

Such as 1/4″-20, 3/4″-10, 1″-8, 1/4″-20 means the nominal size is 1/4, that is, the major diameter is 6.35mm (25.4 divided by 4=6.35) 20 teeth per inch, So on and so forth.


American standard pipe thread(NPT)

Post time: Sep-11-2020
WhatsApp Online Chat !