Product Knowledge and Product Standards of Fasteners

Fasteners are a type of mechanical part used for fastening and are widely used. The characteristics of fasteners: Variety of specifications, performance and use of different, and standardization, serialization, generalization of a very high degree. Therefore, it is also known as a standard fastener for a type of fastener that already has a national (industry) standard, or simply a standard part.

The specific requirements for each specific fastener product's specifications, dimensions, tolerances, weights, performance, surface conditions, marking methods, and inspection, marking, and packaging items are specified separately in several national (industry) standards. For example, there are English, German and American systems.

Fasteners are the most widely used mechanical basic parts. With China's accession to the WTO in 2001 and entering the ranks of major countries in international trade. Fast fastener products that are exported to fasteners in many countries in the world and countries in the world are also pouring into the Chinese market. Fasteners, as one of the products with a large volume of imports and exports in China, are in line with international standards. They are of great significance to the promotion of China's fastener companies to the world and the promotion of the full participation of fastener companies in international cooperation and competition. Strategic significance.

A fastener is a general term for a type of mechanical part used when two or more parts (or components) are fastened together to form a whole. Also known as standard parts in the market.

It usually includes the following 12 types of parts:

1. Bolt: A type of fastener consisting of a head and a threaded rod (cylindrical body with an external thread) that is to be fitted with a nut and used 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 that is threaded at both ends. When connected, one end must be screwed into the part with the internally threaded hole and the other end through the part with the through hole, and then the nut is screwed on even if the two parts are fastened together in one piece. This type of connection is called a stud connection and it is also a detachable connection. It is mainly used for occasions when one of the connected parts has a large thickness, requires a compact structure, or is frequently used for bolting because of frequent disassembly.

3. Screw: It is also a kind of fastener that consists of two parts: the head and the screw. It can be divided into three categories according to the purpose: machine screws, set screws and special purpose screws. The machine screw is mainly used for a part with a tight threaded hole, and a fastening connection with a part with a through hole, and does not require a nut to fit (this type of connection is called a screw connection and is also a detachable connection; it can also be Fits with a nut for fastening connections between two parts with through holes.) Set screws are used to fix the relative position between two parts. Special-purpose screws such as eyebolts are used for lifting parts.

4. Nuts: with internal threaded holes, the shape is generally shown as a flat hexagonal column, there are also flat square cylindrical or flat cylindrical, with bolts, studs or machine screws, used to fasten the connection of two parts, so that It becomes a whole.

5. Self-tapping screws: Similar to machine screws, but the thread on the screw is a special thread for tapping screws. It is used to fasten and connect two thin metal components into a single piece. The small holes need to be made in advance on the components. Because the screws have a high hardness, they can be screwed directly into the holes of the components to make the components Responsive internal threads are formed. This type of connection is also a detachable connection.

6. Wood screws: similar to machine screws, but the thread on the screw is a special wood screw with a rib that can be screwed directly into a wooden member (or part) for a metal with a through hole (or non-metal) The parts are fastened together with a wooden member. This connection is also a detachable connection.

7. Washer: A type of fastener that is oblate in shape. Placed between the supporting surface of the bolt, screw or nut and the surface of the connecting part, play the role of increasing the contact surface area of ​​the connected parts, reducing the pressure per unit area and protecting the surface of the connected parts from being damaged; another type of elastic gasket, Can also play a role in preventing the nut from loosening.

8. Retaining ring: It is installed in the axis groove or hole groove of the machine and equipment and plays the role of blocking the left and right movement of the part on the shaft or hole.

9. Pin: Mainly used for positioning of parts, 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 parts (or components) that connect two through-holes to make it a unitary body. This type of connection is called rivet connection, or simply riveting. Generic and non-detachable connection. Because the two parts that are connected together must be separated, the rivet on the part must be destroyed.

11. Assemblies and connectors: Assemblies refer to a type of fastener that is supplied in combination, such as a combination of a machine screw (or bolt, self-provided screw) and a flat washer (or spring washer, lock washer); Sub-finger A type of fastener that supplies a special combination of bolts, nuts, and washers, such as high-strength large hex head bolts for steel structures.

12. Weld nails: Because of the different types of fasteners made up of light energy and nail heads (or no nail heads), they are fixedly attached to a part (or component) by welding so that they can be connected to other parts.

Each fastener product has to involve several aspects of the standard:

1) Standards for dimensions of fasteners: Specify the basic dimensions of the product. Threaded products also include the basic dimensions of the thread, thread tails, shoulders, undercuts and chamfers, and ends of externally threaded parts. Size and other aspects.

2) Standards for technical conditions of fastener products. Specific includes the following criteria:
a) Standards for fastener product tolerances: Specify the product size tolerances and geometric tolerances.
b) Standards for the mechanical properties of fasteners products: Specify the marking methods for the mechanical performance grades of the products and the contents of the mechanical performance items and requirements; some fasteners will change the content of the fasteners to the material properties or working performance of the products. Aspect content.
c) Standards for surface defects of fastener products: Specify the types of surface defects and specific requirements of the product.
d) Standards for surface treatment of fasteners: Specify the type of surface treatment and specific requirements of the product.
e) Standards for the testing of fastener products: Specify the content of the above-mentioned various performance requirements for testing.

3) Standards for acceptance inspection, marking and packaging of fastener products: Specify the quality level and sampling plan of the qualified products during the inspection and acceptance of the products, and the contents of the product marking methods and packaging requirements.

4) Standards for Marking Methods of Fastener Products: Specifies the contents of the complete marking method and simplified marking method of the product.

5) Other aspects of the standard for fasteners: standards for fastener terms, weight standards for fasteners, etc.