Fastener features, functions, standards, specifications, and classification
A fastener is a generic term for a class of mechanical parts used to securely join two or more parts (or components) into one piece. Fasteners are a class of mechanical parts that are used for fastening connections and are extremely versatile. A wide variety of fasteners can be found on a variety of machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, meters and supplies. It is characterized by a wide variety of specifications, different performance uses, and the degree of standardization, serialization, and generalization is also extremely high. Therefore, some types of fasteners with existing national standards are also referred to as standard fasteners, or simply as standard parts. Fasteners include: bolts, studs, screws, nuts, washers, pins Fasteners, also known as standard parts on the market. It is a kind of mechanical parts used for fastening and connection. It is widely used. The characteristics of fasteners are various specifications and different performances, and the degree of standardization, serialization and generalization is extremely high. Therefore, some people have referred to a type of fastener that has the national (industry) standard as a standard fastener, which is simply referred to as a standard component. Due to the specifications, dimensions, tolerances, weights, performance, surface conditions, marking methods, and specific requirements of inspection and inspection, marking and packaging for each specific fastener product, it is specified in several national (industry) standards. For example, there are English, German and American systems. Fasteners are the most widely used mechanical foundation. As China joined the WTO in 2001 and entered the ranks of international trade powers. China's fastener products are exported to the world, and fastener products from all over the world are also pouring into the Chinese market. As one of the products with a large import and export volume in China, fasteners are in line with international standards, and it is of great significance to promote the Chinese fastener enterprises to the world and promote the full participation of fastener enterprises in international cooperation and competition. Strategic significance. A fastener is a general term for a type of mechanical part that is used to securely join two or more parts (or components) together. The market is also known as standard parts. 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 an external thread). It is required to be fitted with a nut for fastening two parts with through holes. This type of connection is called a bolted connection. If the nut is unscrewed from the bolt, it is possible to separate the two parts, so the bolt connection is a detachable connection. 2. Stud: A type of fastener that has no head and only has threads on both ends. When connecting, one end must be screwed into the part with the internally threaded hole, the other end is passed through the part with the through hole, and then the nut is screwed, even if the two parts are fastened together as a whole. This type of connection is called a stud connection and is also a detachable connection. It is mainly used for the case where one of the connected parts has a large thickness, requires a compact structure, or is not suitable for bolting due to frequent disassembly. 3. Screw: It is also a kind of fastener consisting of two parts, head and screw. It can be divided into three categories according to the purpose: machine screw, set screw and special purpose screw. The machine screw is mainly used for a tightly threaded part and a tight connection between a part with a through hole and does not require a nut fit (this type of connection is called a screw connection and is also a detachable connection; Fitted with a nut for a secure connection between two parts with through holes.) The set screw is primarily used to secure the relative position between the two parts. Special purpose screws such as eyebolts are used for lifting parts. 5. Self-tapping screws: Similar to machine screws, but the threads on the screw are dedicated self-tapping screws. It is used to fasten and connect two thin metal members to make them a whole. The components need to be made into small holes in advance. Because of the high hardness of the screws, they can be directly screwed into the holes of the components. Form a responsive internal thread. This type of connection is also a detachable connection. 6. Wood screws: Also similar to machine screws, but the threads on the screw are special wood screws with ribs that can be screwed directly into the wooden component (or part) for a metal (or non-metal) with a through hole. The parts are fastened together with a wooden component. This connection is also a detachable connection. 7. Washer: A type of fastener that is oblate in shape. Between the support surface of the bolt, the screw or the nut and the surface of the connecting part, it increases the contact surface area of ​​the connected part, reduces the pressure per unit area and protects the surface of the connected part from damage; another type of elastic washer, It also acts to prevent the nut from loosening. 8. Retaining ring: It is installed in the shaft groove or hole of the machine and equipment, and plays the role of preventing the left and right parts of the shaft or the hole from moving. 9. Pin: It is mainly used for part positioning, and some can also be used for connecting parts, fixing parts, transmitting power or locking other fasteners. 10. Rivet: A type of fastener consisting of two parts, the head and the shank, used to fasten the two parts (or components) with through holes to make them integral. This type of connection is called a rivet connection, referred to as riveting. Dependent and non-detachable connection. Because the two parts that are joined together must be separated, the rivets on the part must be destroyed. 11. Assembly and connection pair: The assembly refers to a type of fastener supplied in combination, such as a certain machine screw (or bolt, self-supply screw) combined with a flat washer (or spring washer, lock washer); A pair of fasteners that supply a combination of special bolts, nuts, and washers, such as high-strength large hex head bolts for steel structures. 12. Solder Nail: Due to the different types of fasteners consisting of light energy and nail head (or no nail head), it is fixedly attached to a part (or component) by welding to connect with other parts. Each fastener product involves several standards for several aspects : (1) Standards for fastener product size: specify the basic dimensions of the product; threaded products, including basic thread size, thread finish, shoulder distance, undercut and chamfer, external threaded parts End size and other aspects. (2) Standards for technical conditions of fastener products. Specifically, it includes the following standards: a. Standards for fastener product tolerances: specify the tolerances and shape tolerances of the product dimensions. b. Standards for mechanical properties of fastener products: specific marking methods for mechanical performance grades of products and mechanical performance items and requirements; some fastener products change this content to product material properties or work performance. Aspect of the content. c. Standards for surface defects of fastener products: specify the types of surface defects and specific requirements of the products. d. Standards for surface treatment of fastener products: specify the types of surface treatment and specific requirements of the products. e. Standards for testing fastener products: specify the test content of the above various performance requirements. (3) Standards for acceptance inspection, marking and packaging of fastener products: specify the quality level and sampling plan of the project, and the content of the product marking method and packaging requirements. (4) Standards for marking methods for fastener products: specific provisions for the complete labeling method of products and simplified marking methods. (5) Other aspects of fasteners: standards such as fastener terminology, standards for fastener product weight, etc.
4. Nut: With internal threaded hole, the shape is generally flat hexagonal column shape, but also has a flat square column or a flat cylindrical shape. It is matched with bolts, studs or machine screws for fastening two parts. It becomes a whole.