Different Thread Typies，Such as PT Thread, NPT Thread, G Thread, and Metric Thread is Worth Learning

NPT, PT, G are all pipe threads. Now we will introduce information about thread type to you. 

NPT is the abbreviation of National (American) Pipe Thread. It is a standard American 60 degree taper pipe thread. It is used in North America. The national standard can be consulted in GB / T12716. 



PT is the abbreviation of Pipe Thread, which is a 55 degree sealed conical pipe thread. It belongs to Wyeth thread family and is widely used in Europe and some Commonwealth countries.

G is a 55 degree non-threaded sealed pipe thread, and it belongs to the Wyeth thread family. It is marked as G, which represents cylindrical thread. The national standard can be found in GB/T7307.

In addition, 1/4, 1/2 and 1/8 in thread refer to the diameter of thread size, and the units used are inch. Insiders usually use the points to refer to the thread size, one inch is equal to 8 points, 1/4 inch is 2 points, and so on.

G is the general designation of pipe threads (Guan). The division of 55 and 60 degrees is functional, commonly known as the pipe circles. That is, the thread is made from a cylindrical surface.

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

Metric threads are represented by pitch, threads are expressed in terms of the number of threads per inch in America and Britain. This is the most important difference between them.

The metric thread is a 60-degree equilateral tooth type, the inch thread is an isosceles 55-degree tooth type, and American standard thread is 60 degrees.

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

The pipe thread is mainly used for the connection of the pipe, and the inner and outer threads are closely matched, and there are two kinds of pipes which are straight pipe and tapered pipe. The nominal diameter refers to the diameter of the pipe which is connected, and the diameter of the thread is obviously larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameters of inch screw threads, and its unit is inch.

The angle of the thread: Both metric and American threads are 60 degrees, the inch system thread is 55 degrees, the TM pipe thread is 30 degrees, both SM needle thread and BC thread are 60 degrees, the metric trapezoidal thread is 30 degrees, the English trapezoidal thread is 29 degrees, the table thread is TW29 degrees or TM30 degrees.

Regular screw thread: Metric thread M; inch system thread W; American system UNC, UNE, UNEF.

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

Tuyere screw 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 screw thread: Formulating specifications in terms of nominal size and the number of teeth per inch.

For example, 1/4 "-20, 3/4" -10, 1 "-8, 1/4" -20 represents the nominal size 1/4, and the big diameter is 6.35mm (25.4 except 4=6.35) 20 teeth per inch, and so on.

The brief size of the NPT thread

size of pipe and tubing (in)		1/16	1/8	1/4	3/8	1/2	3/4	1	1¼	1½	2	2½
External diameter of tube	in	0.3125	0.405	0.54	0.675	0.84	1.05	1.315	1.66	1.9	2.375	2.875
	im	7.9	10.3	13.7	17.1	21.3	36.7	33.4	42.2	48.3	60.3	73
Number of teeth per inch		27		18		14		11½				8
Pitch: mm		0.9408		1.4102		1.814		2.209				3.175
Rotation length: mm		4.064	4.102	5.786	6.096	8.128	8.611	10.16	10.668		11.074	17.323
Middle circumflex diameter: mm		7.142	9.489	12.487	15.926	19.771	25.117	31.462	40.218	46.287	58.325	70.159

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