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Differential introduction of thread and pipe thread

Thread and pipe thread
The history of the standard of thread and thread
Thread is one of the earliest machines invented by man. In ancient times, people used thread to fix armour and wine.
In 1841, the British man Whitworth proposed the world's first threaded national standard (B.S.W. and B.S.F.) to lay a technical system for the standard of thread. In 1905, the British man Taylor invented the design principle of the thread gauge (Taylor principle). Britain has become the first country in the world to fully grasp the thread processing and testing technology, and the British tube thread has been widely popularized with the rise of the "sunset Empire".
The American thread standard (N) is developed on the basis of Wyeth thread in Britain. After the Second World War, it turned into a unified thread (UN) used jointly by the allies of World War II. The American pipe thread and the British pipe thread are the two pillars of the world's pipe thread standard.
The common thread of rice is derived from the American National thread (N). It has been widely used in the European continent and incorporated into the ISO standard. When the system of public units is determined as an international legal measurement unit, it has further promoted the status of the common thread in the international trade.
Two, pipe thread
The British pipe thread originates from the British Wyeth thread. The line series of Wyeth thread and the Wyeth thread combination set up the basic dimensions of the British tube thread. According to the 1/16 taper relationship, the non sealed tube thread series (BSP Series) of Wyeth thread was put forward in 1940; in 1956, the British non sealed tube thread standard (BS 2779) was issued separately. ).
The British tube thread in the ISO standard has been transformed into a metric unit. The metric method of the British tube thread is very simple. The inch size of the original pipe thread is multiplied by 25.4 to the millimeter size.
There are two modes of fit for the British sealed pipe thread, "column / cone" and "cone / cone". Two kinds of English sealed pipe threads use different thread ring rules (cylindrical screw ring gauge and conical thread ring gauge) and threaded plug gauge (the position of reference plane is different, the base plane is separated by half teeth). European countries mainly use "column / cone" coordination. Thread and thread are used in countries outside Europe.
The English seal pipe thread is the seal pipe thread for the general purpose. It is necessary to add the sealing material to the thread pair in the use. Its characteristic is that it is more economical and the machining precision is moderate. The thread of the sealed connection can be ensured to the dry sealing pipe thread without sealing the material. There is no dry seal thread in the system of the British pipe thread.
The sealing tube thread has two functions of mechanical connection and sealing, but the non sealing pipe thread has only one kind of function connected mechanically. So the precision of the thread of the seal pipe should be stricter than the precision of the thread of the non sealed tube.
The general purpose pipe thread of American system was put forward in 1840 by Robert. In 1919, the general use seal pipe thread was promulgated as the national standard of the United States ASA B2.1-19191945. The United States put forward the thread of dry seal tube, and then issued the national standard of the dry seal pipe thread.
In 1973, China began to set up the standard of rice cone thread. In 1978, the standard of rice cone thread (GB 1415) and the standard of non sealed tube thread (GB 1414, line series of common thread) were issued in 1992 and 2003, two national standards were revised respectively.
Three. The corresponding relationship between the current pipe threads.
Standard British tube thread 55 degrees
The taper is 0 degrees in the American tube thread 60 degrees
Taper 1:16 meter / metric tube thread 60 degrees
Taper 0 degrees
Non sealed cylindrical thread threads, general sealing tapered tube threads, unsealed pipe threads
External thread internal thread external thread internal thread internal thread
Pipe thread standard G NPT M
The connection mode of the valve body and the pipeline mainly adopts the British non sealed cylindrical inner tube thread, that is, G thread, the American system is generally sealed with the NPT thread of the inner tube of the conical tube, and the non sealed internal thread M thread (nominal diameter mm * pitch mm);
In addition, there are PT thread: conical pipe thread, tooth shape angle 55 degree taper 1:16, national standard can be consulted GB/T7306-2000.
RC thread: 55 degree sealed conical inner thread, tooth shape angle 55 degree, taper 1:16 ISO7-1:1994 standard;

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