BSPT and BSP British Specification Taper Threads
NPT US specification taper thread
PT Japan's old JIS standard taper thread, equivalent to ISO standard R, Rc
DIN2999 European, mainly German pipe threads
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NPT
NPT is the general-purpose American standard tapered pipe thread.
Among them, N means National (American) American national standard, P means PIPE pipe, T means TAPER taper, and the tooth profile angle is 60°.
This type of pipe thread is commonly used in North America or is often seen using ANSI specifications. The national standard can be found in GB/T12716-1991
I must note: NPT teeth must be used when doing ANSI specifications!
PT
PT thread is an imperial tapered thread with a thread angle of 55°, which is most commonly used in sealing. It is mostly used in European and Commonwealth countries. In fact, the Japanese JIS standard in Taiwan also follows the imperial standard, and China actually also uses the imperial thread. Belongs to the Whitworth thread family. The national standard can be found in GB/T7306-2000.
British pipe threads are fine threads. Because the thread depth of coarse threads is large, it will seriously reduce the strength of the outer diameter pipe being cut.
In addition, NIPPLE is often used in actual small-diameter pipelines. The purpose is that the wall thickness of purchased NIPPLE is relatively thick, which can ensure the strength of the tapping part. At the same time, the main pipeline does not require thick pipe walls. This is To save costs.
PF thread is a parallel thread for pipes.
I must note: PT teeth, etc. must be used when doing JIS specifications!
G
G is a 55-degree non-threaded sealing pipe thread, which belongs to the Whitworth thread family. Marked G stands for cylindrical thread. The national standard can be found in GB/T7307-2001
G is the general name for pipe threads (Guan). The divisions of 55 and 60 degrees are functional and commonly known as pipe circles. That is, the thread is machined from a cylindrical surface.
ZG
ZG is commonly known as pipe cone, that is, the thread is processed from a conical surface. General water pipe joints are like this. The old national standard is marked Rc
Metric threads are expressed by pitch, and American and British threads are expressed by the number of threads per inch. This is their biggest difference. Metric threads are 60-degree equilateral profile, British threads are isosceles 55-degree profile, and American threads are 60 degrees.
Metric threads use metric units, and American and British threads use imperial units.
Pipe threads are mainly used to connect pipes. The internal and external threads are closely matched, and there are two types: straight pipes and tapered pipes. The nominal diameter refers to the diameter of the connected pipe. Obviously the major diameter of the thread is larger than the nominal diameter. 1/4, 1/2, and 1/8 are the nominal diameters of inch threads in inches.
Identification of inch uniform threads
Inch system unified threads are widely used in inch system countries. This type of thread is divided into three series: coarse thread series UNC, fine thread series UNF, extra fine thread series UNFF, plus a fixed pitch series UN.
Marking method: Thread diameter-number of threads per inch Series code-accuracy level
Example: Coarse tooth series 3/8-16 UNC-2A
Fine tooth series 3/8-24 UNF-2A
Extra fine tooth series 3/8-32 UNFF-2A
Fixed pitch series 3/8-20 UN-2A
The first digit 3/8 represents the outer diameter of the thread in inches. To convert to the metric unit Mm, multiply by 25.4, that is, 3/8×25.4=9.525mm; the second and third digits 16, 24, 32, and 20 are The number of teeth per inch (the number of teeth on a length of 25.4mm); the text codes after the third digit, UNC, UNF, UNFF, UN, are the series codes, and the last two digits, 2A, are the accuracy level.
Conversion of 55° cylindrical pipe thread
The 55° cylindrical pipe thread comes from the inch series, but is widely used in both metric and inch countries. It is used to connect pipe joints and pipes for transporting liquids, gases and installing wires. However, the codes of different countries are different, so you should press The foreign codes in the table (comparison table) are converted into Chinese codes. The 55° cylindrical pipe thread codes of various countries are now listed in the table below.
Country code
China G
Japan G, PF
UK BSP, BSPP
France G
Germany R (internal thread), K (external thread)
Former Soviet Union G, TPУБ
ISO Rp
Conversion of 55° tapered pipe thread
55° tapered pipe thread means that the thread profile angle is 55° and the thread has a taper of 1:16. This series of threads are widely used in the world. Its code names vary from country to country, as shown in the table below. Convert the foreign code names in the table to Chinese code names.
Country code
China ZG, R (external thread)
British BSPT, R (external thread), Rc (internal thread)
France G (external thread), R (external thread)
Germany R (external thread)
Japan PT, R
ISO R (external thread), Rc (internal thread)
Conversion of 60° tapered pipe thread
60° tapered pipe thread refers to a pipe thread with a profile angle of 60° and a thread taper of 1:16. This series of threads are used in my country's machine tool industry and the United States and the former Soviet Union. Its code name, our country used to specify it as K, later specified it as Z, and now it is changed to NPT. See the thread code comparison table below.
Country code
China Z(old) NPT(new)
United States NPT
Soviet B
Conversion of 55° trapezoidal thread
Trapezoidal thread refers to a metric trapezoidal thread with a profile angle of 30°. This series of threads are relatively uniform at home and abroad, and their codes are also quite consistent. The thread codes are shown in the table below.
Country code
China T(old) Tr(new)
ISO Tr
Germany TR
Former Soviet Union TR
Thread type
According to different uses of threads, they can be divided into:
1. International Metric Thread System:
The thread adopted by my country's national standard CNS. The top of the tooth is flat and easy to turn, while the bottom of the tooth is arc-shaped to increase the strength of the thread. The thread angle is 60 degrees, and the specification is expressed in M. Metric threads can be divided into two types: coarse thread and fine thread. The representation is as M8x1.25. (M: code, 8: nominal diameter, 1.25: pitch).
2. American Standard Thread:
The top and root of the thread are both flat and have better strength. The thread angle is also 60 degrees, and the specifications are expressed in threads per inch. This kind of thread can be divided into three levels: coarse thread (NC); fine thread (NF); extra fine thread (NEF). The representation is such as 1/2-10NC. (1/2: outer diameter; 10: number of teeth per inch; NC code).
3. Unified Thread:
Jointly formulated by the United States, the United Kingdom, and Canada, it is the commonly used British thread.
The thread angle is also 60 degrees, and the specifications are expressed in threads per inch. This kind of thread can be divided into coarse thread (UNC); fine thread (UNF); extra fine thread (UNEF). The representation is such as 1/2-10UNC. (1/2: outer diameter; 10: number of teeth per inch; UNC code)
4. V-shaped thread (Sharp V Thread):
The top and roots are both pointed, weak in strength, and not commonly used. The thread angle is 60 degrees.
5. Whitworth Thread:
Thread adopted by British National Standard. The thread angle is 55 degrees, represented by the symbol "W".
Suitable for rolling manufacturing. The representation is as W1/2-10. (1/2: outer diameter; 10: number of teeth per inch; W code).
6. Knuckle Thread:
It is the standard thread specified by German DIN. Suitable for connecting light bulbs and rubber tubes. The symbol is "Rd".
7. Pipe Thread:
Threads used to prevent leakage are often used to connect gas or liquid pipe fittings. The thread angle is 55 degrees and can be divided into straight pipe threads codenamed "P.S., N.P.S." and inclined pipe threads codenamed "N.P.T.". The taper is 1:16, which is 3/4 inch per foot.
8. Square Thread:
The transmission efficiency is high, second only to the ball thread, but its disadvantage is that it cannot be adjusted with a nut after wear. Generally used for the screw of vise and the thread of crane.
9. Trapezoidal Thread:
Also known as Acme thread. The transmission efficiency is slightly lower than that of square thread, but it can be adjusted with a nut after wear. The thread angle of the metric system is 30 degrees, and the thread angle of the imperial system is 29 degrees. Generally used in lathe lead screws. The symbol is "Tr".
10. Zigzag thread (Buttress Thread):
Also known as rhombic thread, it is only suitable for one-way transmission. Such as screw jacks, pressurizers, etc. The symbol is "Bu".
11. Ball thread:
It is the thread with the best transmission efficiency. It is difficult to manufacture and extremely costly. It is used in precision machinery. Such as the lead screw of CNC machine tools.
Representation of inch bolts:
LH 2N 5/8 × 3 - 13 UNC-2A
(1)LH is left thread (RH is right thread, can be omitted).
(2) 2N double thread thread.
(3)5/8 inch thread, 5/8" outer diameter.
(4)3 bolt length 3".
(5)13 threads have 13 threads per inch.
(6)UNC unified standard thread coarse thread.
(7) Level 2 fit, external thread (3: tight fit; 2: medium fit; 1: loose fit) A: external thread (can be omitted)
B: Internal thread
Imperial thread:
The size of inch threads is usually expressed by the number of threads per inch of thread length, referred to as "number of threads per inch", which is exactly the reciprocal of the thread pitch. For example, a thread with 8 threads per inch has a pitch of 1/8 inch.