1: Development history: After the first industrial revolution, Britain laid a technical system for thread standards. The United States developed the American thread standards based on the British Wyeth thread. The ordinary metric thread originated from American threads and was widely used in Europe and its status was in accordance with the metric unit system. Confirm and improve.
2: Metric thread: metric thread, a standard thread, also known as metric thread. (GB/T 192-20031. Metric ordinary threads are represented by capital M. Metric threads are 60-degree equilateral tooth type. Metric threads are represented by pitch. Metric units (such as mm) are used. Metric ordinary threads are divided into coarse teeth according to pitch. There are two types of thread and fine thread. The common thread marking of coarse teeth generally does not indicate the thread pitch, such as M20 represents coarse thread; the fine thread marking must indicate the thread pitch, such as M30x1.5 represents fine thread, of which the nominal diameter is 30mm, and the thread pitch is It is p=1.5. Ordinary threads are used for connection and tightening between mechanical parts. Generally, thick threads are used for thread connections. Fine threads are slightly stronger than coarse threads of the same nominal diameter, and have better self-locking performance.
3: English thread: English thread is an isosceles 55-degree tooth type. English thread is represented by the number of threads within each inch. Use English units (such as inches), such as: 1/2-14, which means that the thread size is 1. /2 inches, 14 threads per inch. BSPP is a 55-degree non-threaded sealed pipe thread, belonging to the Wyeth thread family, and the conical internal thread is marked as RP. The national standard is G, which represents cylindrical thread. National Standards are available for GB/T7307-2001. Its corresponding ISO standard is ISO228/1. PT (BSPT) is the abbreviation of Pipe Thread, which is a 55-degree sealed conical pipe thread, with a taper of 1:16, and the inclination angle of the thread is: 1 ° 47′. It belongs to the Wyeth thread family, mostly used in European and Commonwealth countries, and is often used in Water and gas pipe industry, national standard reference GB/T7306-2000. It was previously called ZG in China. Now consistent with the ISO standard (ISO 7/1), codenamed R (RT). Conical internal thread Rc; conical external thread R (old standard: PT) Main differences: metric threads are represented by pitch, the number of internal threads per inch for US and English use; metric 60-degree equilateral tooth type, English isosceles 55-degree, American etc. Waist 60 degrees; metric units are used in metric units, and metric units are used in US and English.
4: American threads: American standard pipe threads (ANSIB1.20) and American unified thread standards (UN series) (ANSIB1.1). American threads are isosceles 60-degree tooth type, American threads are represented by the number of threads within each inch. American threads are made of English units (such as inches) NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree vertebrae. The inclination angle of the pipe thread is: 1°47'. Used in North America, national standard reference GB/T12716
