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Fastener terminology standards and types of standard parts

Update:19-01-2020
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Standard parts are simply fasteners with fixed specific […]

Standard parts are simply fasteners with fixed specifications, shapes, and materials. They are also called fasteners on the market. It is a class of mechanical parts used for fastening and connection, which is extremely widely used. Features of fasteners: a large variety of specifications, different performance and use, and a high degree of standardization, serialization, and generalization. Therefore, some people also refer to a class of fasteners that already have national (industry) standards as standard fasteners, referred to as standard components for short. Due to the specific requirements of each specific fastener product's specifications, dimensions, tolerances, weights, properties, surface conditions, marking methods, and acceptance inspection, marking, and packaging items, it is specified in several national (industry) standards. , Such as British, German, and American. Fasteners are the most widely used mechanical base parts. With China's entry into the WTO in 2001 and entering the ranks of major international trading countries. China's fastener products are exported to a large number of countries in the world, and fastener products from all over the world also continue to flood into the Chinese market. Fasteners, as one of the products with a large import and export volume in China, are in line with international standards. It is of great significance to promote the development of Chinese fastener companies into the world and promote the full participation of fastener companies in international cooperation and competition. Strategic significance. Fasteners are a general term for a class of mechanical parts used when two or more parts (or components) are fastened and connected to form a whole. They are also called standard parts in the market.
Standard part types It usually includes the following 12 types of parts:
1. Bolt: a type of fastener consisting of a head and a screw (a cylinder with external threads), which need to cooperate with a nut to fasten two parts with through holes. This type of connection is called a bolted connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.
2. Stud: A type of fastener without a head and only with external threads at both ends. When connecting, one end must be screwed into the part with the internal threaded hole, the other end is passed through the part with the through hole, and then the nut is screwed on, even if the two parts are firmly connected as a whole. This type of connection is called a stud connection and is also a detachable connection. It is mainly used in the case where one of the connected parts has a large thickness, requires a compact structure, or is not suitable for bolt connection due to frequent disassembly.
3. Screw: It is also a type of fastener consisting of the head and the screw. It can be divided into three categories according to its purpose: machine screws, set screws and special-purpose screws. The machine screw is mainly used for a tight connection between a threaded hole part and a part with a through hole, and does not require a nut. (This type of connection is called a screw connection, which is also a detachable connection; it can also be Cooperate with the nut for fastening connection between two parts with through holes.) Set screws are mainly used to fix the relative position between the two parts. Special-purpose screws such as eyebolts are used for lifting parts.
4. Nut: with internal threaded holes, generally in the shape of a flat hexagonal column, but also a flat square or flat cylindrical shape, with bolts, studs or machine screws, used to fasten the two parts, so that It becomes a whole.
5. Self-tapping screws: Similar to machine screws, but the threads on the screw are special threads for self-tapping screws. It is used to fasten and connect two thin metal members into one piece. Small holes must be made in advance on the member. Because this screw has high hardness, it can be screwed directly into the hole of the member to make the member Form a responsive internal thread. This type of connection is also a detachable connection.
6. Wood screw: It is similar to machine screw, but the thread on the screw is a special rib for wood screw, which can be directly screwed into the wooden member (or part), and used to insert a metal (or non-metal) with a through hole. The parts are fastened to a wooden member. This connection is also a detachable connection.
7. Washer: a type of fastener with a flat circular ring shape. It is placed between the support surface of the bolt, screw or nut and the surface of the connecting part, and it plays the role of increasing the contact surface area of ​​the connected part, reducing the unit area pressure and protecting the surface of the connected part from being damaged; another type of elastic washer, It can also play a role in preventing the nut from loosening.
8. Retaining ring: It is installed in the shaft groove or hole groove of the machine or equipment, and plays a role of preventing the parts on the shaft or hole from moving left and right.
9. Pins: mainly used for positioning parts, and some can also be used for parts connection, fixing parts, transmitting power or locking other fasteners.
10. Rivets: A type of fastener consisting of a head and a nail rod. It is used to fasten two parts (or components) with through-holes into one piece. This type of connection is called rivet connection, or riveting for short. Is a non-detachable connection. Because the two parts connected together must be separated, the rivets on the parts must be destroyed.
11. Assembly and connection pair: Assembly refers to a type of fasteners supplied in combination, such as the combination of a certain type of machine screws (or bolts, self-supplied screws) and flat washers (or spring washers, lock washers); connection Vice refers to a class of fasteners that are supplied with a combination of certain special bolts, nuts and washers, such as steel structures with high-strength large hexagon head bolts connected to the vice.
12. Welding nail: Due to the heterogeneous fastener composed of light energy and nail head (or no nail head), it is fixedly connected to one part (or component) by welding method so as to be connected with other parts.

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