BSPT and BSP—British Specification for Tapered Threads
NPT - American Standard Tapered Thread
PT - Japan's old JIS standard taper thread, equivalent to R, Rc of ISO standard
DIN2999——European mainly German pipe thread
NPT is the American Standard Taper Pipe Thread for general use.
Among them, N means National (American) American national standard, P means PIPE pipe, T means TAPER cone, and the tooth angle is 60°.
This type of pipe thread is commonly used in North America, or is often seen using ANSI specifications. National standards can be found in GB/T12716-1991
I must pay attention: NPT teeth must be used in the ANSI specification!
PT
The PT tooth is an imperial tapered thread, and the tooth angle is 55°, which is the most commonly used in sealing. It is mostly used in Europe and the Commonwealth of Nations. In fact, the JIS standard in Taiwan and Japan also follows the British standard, while China actually uses the British standard thread. It belongs to the Whitworth thread family. National standards can be found in GB/T7306-2000.
The British pipe thread is a fine thread, because the tooth depth of the coarse thread will seriously reduce the strength of the pipe with the outer diameter of the cut thread.
In addition, NIPPLE is often used in the actual distribution of small-diameter pipelines. The purpose is that the wall thickness of the purchased NIPPLE is relatively thick, which can ensure the strength of the tapping part. At the same time, the main pipeline does not need thick pipe walls. In order to save costs.
PF teeth are parallel threads for pipes.
We must pay attention: PT teeth must be used in making JIS specifications, etc.!
G is a 55-degree non-threaded sealing pipe thread, which belongs to the Whitworth thread family. Marked as G stands for cylindrical thread. National standards can be found in GB/T7307-2001
G is the general name of pipe thread (Guan), and the division of 55 and 60 degrees is functional, commonly known as pipe circle. That is, the thread is machined from a cylindrical surface.
ZG
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. The old national standard is marked as Rc
The metric thread is represented by the pitch, and the American and British thread is represented by the number of thread teeth per inch. This is the biggest difference between them. The metric thread is a 60-degree equilateral tooth type, and the British system is an isosceles 55-degree tooth type. The American thread 60 degrees.
Use metric units for metric threads and imperial units for US and British threads.
Pipe thread is mainly used for the connection of pipes, and its internal and external threads are closely matched, and there are two types of straight pipe and tapered pipe. 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, 1/8 are the nominal diameters of British thread, in inches.
Identification of Inch Unified Threads
The size of the inch thread is usually expressed by the number of threads per inch of length on the thread, referred to as "threads per inch", which is exactly equal to the reciprocal of the pitch. For example, a thread with 8 teeth per inch has a pitch of 1/8 inch.
Inch system uniform thread is 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 - precision grade
Example: Coarse 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 indicates the outer diameter of the thread, the unit is inches, and the conversion to the metric unit mm is multiplied 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 the length of 25.4mm); the text codes after the third digit UNC, UNF, UNFF, UN are series codes, and the last two digits 2A are precision grades.
Examples of representation of inch bolts:
LH 2N 5/8 × 3 - 13 UNC-2A
(1) LH is left thread (RH is right thread, which can be omitted).
(2) 2N double thread.
(3) 5/8 inch thread, 5/8” OD.
(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.
Conversion of 55°cylindrical pipe thread
55°cylindrical pipe thread is derived from the inch system, but it is widely used in both metric and inch countries. It is used to connect pipe joints and pipes for conveying liquids, gases, and installing wires. However, the codes of various countries are different, and they should be pressed The foreign codes in the table (comparison table) are converted into Chinese codes, and the 55° cylindrical pipe thread codes of various countries are listed in the table below.
country code
China
Japan G, PF
British BSP, BSPP
France
Germany R (internal thread), K (external thread)
Former Soviet Union G, TPУБ
ISO Rp
Conversion of 55°tapered pipe thread
55° conical pipe thread means that the thread angle is 55° and the thread has a taper of 1:16. This series of threads is widely used in the world, and its code name is different from country to country, as shown in the table below. Convert the foreign codes in the table below into Chinese codes.
country code
China ZG, R (external thread)
British BSPT, R (external thread), Rc (internal thread)
France G (external thread), R (external thread)
German R (external thread)
Japan PT, R
ISO R (external thread), Rc (internal thread)
Conversion of 60°conical pipe thread
The 60° conical pipe thread refers to the pipe thread with a thread angle of 60° and a thread taper of 1:16. This series of threads is used in my country's machine tool industry, the United States, and the former Soviet Union. Its code name was defined as K in the past in my country, and later as Z, and now it is changed to NPT. See the table below for the thread code comparison table.
country code
China Z(Old) NPT(New)
United States NPT
soviet union
Transformation of 55° trapezoidal thread
Trapezoidal thread refers to the metric trapezoidal thread with a profile angle of 30°. This series of threads is relatively uniform at home and abroad, and its code names 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
picture
According to the different uses of threads, it 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, and 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 represented by M. Metric threads can be divided into two types: coarse thread and fine thread. Notation such as M8x1.25. (M: Code, 8: Nominal diameter, 1.25: Pitch).
2. American Standard Thread:
Both the top and the root of the thread are flat, with better strength. The thread angle is also 60 degrees, and the specifications are expressed in teeth per inch. This kind of thread can be divided into three grades: coarse thread (NC), fine thread (NF), and extra fine thread (NEF). Notation such as 1/2-10NC. (1/2: outer diameter; 10: teeth per inch; NC code).
3. Unified Thread:
Jointly formulated by the United States, the United Kingdom, and Canada, it is the most commonly used inch thread at present.
The thread angle is also 60 degrees, and the specifications are expressed in teeth per inch. This kind of thread can be divided into coarse thread (UNC); fine thread (UNF); extra fine thread (UNEF). Notation such as 1/2-10UNC. (1/2: outer diameter; 10: teeth per inch; UNC code)
4. V-shaped thread (Sharp V Thread):
Both the top and the root are pointed, the strength is weak, and it is not often used. The thread angle is 60 degrees.
5. Whitworth Thread:
Threads adopted by British National Standards. The thread angle is 55 degrees, and the symbol is "W".
Suitable for rolling method manufacturing. Notation such as W1/2-10. (1/2: outer diameter; 10: teeth per inch; W code).
6. Knuckle Thread:
It is a standard thread set by German DIN. It is suitable for the connection of light bulbs and rubber tubes. The symbol is "Rd".
7. Pipe Thread:
To prevent leakage, it is often used to connect gas or liquid pipe fittings. The thread angle is 55 degrees, which can be divided into straight pipe thread codes "P.S., N.P.S." and inclined pipe thread codes "N.P.T.", and its taper is 1:16, that is, 3/4 inch per foot.
8. Square Thread:
The transmission efficiency is high, second only to the ball thread, and it cannot be adjusted with the nut after wear and tear, which is its disadvantage. Generally used for the screw of the vise and the thread of the crane.
9. Trapezoidal Thread:
Also known as Acme thread. The transmission efficiency is slightly smaller than that of the 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 for the lead screw of lathe. The symbol is "Tr".
10. Buttress Thread:
Also known as oblique thread, it is only suitable for one-way transmission. Such as screw jacks, pressurizers, etc. The symbol is "Bu".
11. Ball thread:
The thread with the best transmission efficiency is difficult to manufacture and the cost is extremely high, so it is used in precision machinery. Such as the lead screw of CNC machine tools.
