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Haiyan Tianqi Fastener Co., Ltd.
  • Add:Jiaxing Haiyan China NO.1-3 Jincheng South road, Qinshan Industrial Zone of Haiyan, Jiaxing
  • Tel:+86-573-86408971
  • Mobile Phone:+86-13606831322
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Do you know the technical terms of fastener screws


Fasteners, also known as standard parts on the market, are a type of mechanical parts used for fastening and connection, and they are widely used. Fasteners have a wide range of specifications, performance and purpose, and the degree of standardization, serialization and generalization is extremely high. Therefore, some people call a type of fasteners that have national (industry) standards as standard fasteners, or standard parts for short. Fasteners are a general term for a type of mechanical parts used when two or more parts (or components) are fastened and connected into a whole.
Because the specifications, dimensions, tolerances, weight, performance, surface conditions, marking methods of each specific fastener product, as well as the specific requirements for acceptance inspection, marking and packaging, are separately stipulated in several national (industry) standards , Such as the British system, the German system and the American system.
Fasteners are the most widely used mechanical basic parts. With my country's accession to the WTO in 2001, it has entered the ranks of major international trading nations. my country's fastener products are exported in large quantities to countries around the world, and fastener products from all over the world are also pouring into the Chinese market. Fasteners, as one of the products with a large import and export volume in my country, are in line with international standards. It is of great significance to promote Chinese fastener companies to the world and promote fastener companies to fully participate in international cooperation and competition. Strategic significance.
Explanation of some screw technical terms
1. Pitch: the axial distance between two adjacent teeth on the median diameter line.
2. Direction of rotation: There are two types of thread: right-hand and left-hand. When the internal and external threads are screwed together, the clockwise screw is right-handed, and the counterclockwise screw is left-handed.
3. Thread: on the surface of a cylinder or cone, a continuous protrusion with a prescribed tooth shape formed along a spiral line.
4. Internal thread: the thread formed on the inner surface of a cylinder or cone.
5. External thread: the thread formed on the outer surface of a cylinder or cone.
6. Effective thread: a screw composed of a complete thread and an incomplete thread, excluding the screw tail.
7. Thread accuracy: a comprehensive index to measure thread quality, which is composed of thread tolerance zone and screwing length.
8. Nominal diameter: the diameter representing the thread size.
9. Major diameter: the diameter of an imaginary cylinder or cone tangent to the top of the external thread or the bottom of the internal thread. It is represented by d (external thread) or D (internal thread).
10. Pitch diameter: the diameter of an imaginary cylinder or cone. The generatrix of the cylinder or cone passes through the place where the grooves and protrusions on the tooth shape are equal in width. This imaginary cylinder or cone is called a median diameter cylinder or cone. Pitch diameter is represented by d2 (external thread) or D2 (internal thread).
11. Minor diameter: the diameter of an imaginary cylinder or cone tangent to the bottom of the external thread or the top of the internal thread. It is expressed by d1 (external thread) or D1 (internal thread).


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