When it comes to fasteners, everyone seems to know a little bit about it. After all, hardware such as screws and nuts are commonplace in life. Fasteners are widely used in many industries. The degree of standardization, serialization and generalization is extremely high.
What Is a Fastener?
Fasteners, also known as standard parts in the market, are a general term for a type of mechanical parts used to fasten two or more parts (or components) into a whole. It is characterized by a wide variety of specifications, different performance uses, and a very high degree of standardization, serialization and generalization. Fasteners are the most widely used mechanical basic parts and are in great demand.
Classification of Fasteners
Includes: Bolts, Studs, Screws, Nuts, Self-Tapping Screws, Wood Screws, Washers, Retaining Rings, Pins, Rivets, Assemblies and Connecting Pair Assemblies, Welding Studs, Wire Thread Inserts.
1. Bolt: It is a type of fastener consisting of a head and a cylinder with an external thread on the screw. It needs to be used in conjunction with a nut to fasten and connect two parts with through holes. Bolted connections are detachable connections.
2. Stud: It is a type of fastener that has no head and only has external threads on both ends. When connecting, one end of it must be screwed into the part with internal threaded hole, the other end through the part with through hole, and then screw on the nut even if the two parts are tightly connected as a whole. The stud connection is also a detachable connection.
3. Screw: It is also a type of fastener consisting of a head and a screw.
According to the purpose, it can be divided into three categories: machine screws, set screws and special purpose screws.
1) Machine screw: It is mainly used for a fastened connection between a part with a fixed threaded hole and a part with a through hole.
2) Set screw: mainly used to fix the relative position between two parts.
3) Special purpose screw: For example, there are lifting ring screws for lifting parts.
4. Nut: with internal thread hole shape, generally in the shape of a flat hexagonal column, but also in the shape of a flat square column or a flat cylindrical shape, with bolts, studs or machine screws, used to fasten and connect two parts, so that the become a whole.
According to the special category, it is divided into 2 categories: high-strength self-locking nuts and nylon self-locking nuts.
1) High-strength self-locking nut: high strength and reliability, used for road construction machinery, mining machinery, vibration machinery and equipment, etc., European technology, less domestic production.
2) Nylon self-locking nut: It is a new type of high-vibration and anti-loosening fastening parts, which can be used in various mechanical and electrical products with a temperature of -50100 ℃. Aerospace, aviation, tanks, mining machinery, automobile transportation machinery, agricultural machinery, textile machinery, electrical products and various types of machinery have a sharp increase in the demand for nylon self-locking nuts, which can prevent major accidents caused by loose fasteners.
5. Self-tapping screw: Similar to machine screw, but the thread on the screw is a special thread for self-tapping screw. It is used to fasten and connect two thin metal members into one piece, and this kind of connection is also a detachable connection.
6. Wood screw: It is also similar to machine screws, but the thread on the screw is a special thread for wood screws, which can be directly screwed into wooden components or parts to connect a metal or non-metal part with a through hole to a wooden screw. The components are fastened together. This connection is also a detachable connection.
7. Washer: It is a type of fastener in the shape of an oblate ring. It is placed between the supporting surface of the bolt, screw or nut and the surface of the connecting parts, which increases the contact surface area of the connected parts, reduces the pressure per unit area and protects the surface of the connected parts from damage. Another type of elastic washer can also play the role of. It has the effect of preventing the nut from loosening.
8. Retaining ring: It is installed in the shaft groove or hole groove of the machine and equipment, and plays the role of preventing the left and right movement of the parts on the shaft or on the hole.
9. Pin: Mainly used for parts positioning, and some are also used for parts connection, fixing parts, transmitting power or locking other fasteners.
10. Rivet: It is a type of fastener consisting of a head and a shank. It is used to fasten and connect two parts or components with through holes to make them a whole. This form of connection is called rivet connection, or riveting for short, which is a non-detachable connection.
11. Assemblies and connecting sub-assemblies: Refers to a type of fasteners supplied in combination, such as certain machine screws or bolts, self-supplied screws and flat washers or spring washers, lock washers are supplied in combination. Connection pair refers to a type of fastener that is supplied by a combination of special bolts, nuts and washers, such as high-strength hexagon head bolt connection pairs for steel structures.
12. Welding nail: It is a heterogeneous fastener composed of light energy and nail head or no nail head, which is fixed and connected to a part or component by welding so as to be connected with other parts.
13. Wire screw sleeve: It is a new type of threaded connection element, which is refined from high-strength, high-precision corrosion-resistant diamond wire. Shaped like a spring, it is installed in a specific screw hole of the base body, and its inner surface forms a standard thread, which can significantly improve the strength and wear resistance of the threaded connection when it is matched with the screw bolt; it is especially commonly used on low-strength materials such as aluminum, magnesium, cast iron, and plastic. The locking type is to add one or several locking rings on the basis of the ordinary type.
Processing Technology of Fasteners
Due to the wide variety of fasteners, the processing techniques involved are also different, but the commonly used techniques are as follows:
1. Pan Yuan: The small steel billet is used as the raw material, and it is heated and rolled to make the Pan Yuan, also known as the wire rod or the coil material.
2. Annealing: A metal heat treatment process in which the metal is slowly heated to a certain temperature, maintained for a sufficient time, and then cooled at a suitable rate (usually slow cooling, sometimes controlled cooling).
3. Pickling: A process method for cleaning metal surfaces using acid solution to remove oxide scale and rust on metal surfaces.
4. Phosphating: It is a process of chemical and electrochemical reaction to form a phosphate chemical conversion film. The phosphating film is used to provide basic protection to the metal, prevent the metal from being corroded, and at the same time play the role of anti-friction and lubrication. It belongs to surface treatment. preprocessing.
5. Saponification: refers to the process of oil hydrolysis reaction under alkali catalysis. The function of saponification is to further increase the lubricating properties of the metal surface, which also belongs to the pretreatment of surface treatment.
6. Drawing: The pre-treated wire is extruded to the desired shape (including appearance and material diameter) with a disc die with a suitable wire diameter.
7. Cold heading: a forging method that uses a die to extrude a metal bar at room temperature. Usually used to make screws, bolts, rivets and nuts, etc., can reduce or replace cutting.
8. Turning: It is a kind of machining, which mainly uses turning equipment to turn workpiece blanks to obtain the ideal workpiece shape.
9. Threading (thread rolling, thread rolling, tapping): Threads are obtained by extruding or cutting material.
10. Heat treatment: a comprehensive process in which the material is heated, kept warm and cooled in a certain medium, and its performance is controlled by changing the surface or internal structure of the material.
11. Surface treatment: It is a process method of artificially forming a surface layer with different mechanical, physical and chemical properties of the substrate on the surface of the basic material. The purpose is to meet the corrosion resistance, abrasion resistance, decoration or other special functional requirements of the product. We often hear hot-dip galvanizing, blue-white zinc plating, bluing, blackening, etc., which are all surface treatment processes.
