What are standard parts? What are the standard parts classification?

Update:03 Aug 2020
Summary:

Standard parts refer to the commonly used parts (parts) […]

Standard parts refer to the commonly used parts (parts), such as threaded parts, keys, pins, rolling bearings, etc., that have been fully standardized in structure, size, drawing, marking and other aspects and produced by professional manufacturers. The broad sense includes standardized fasteners, connectors, transmission parts, seals, hydraulic components, pneumatic components, bearings, springs and other mechanical parts. The narrow sense includes only standardized fasteners. Standard parts commonly known in China are the abbreviations of standard fasteners, which are a narrow concept, but the existence of a broad concept cannot be ruled out. In addition, there are industry standard parts, such as automobile standard parts, mold standard parts, textile machinery, engineering machinery, etc., which also belong to broad standard parts.
Narrowly defined standard parts are standardized fasteners, which are actually a kind of connecting parts (connecting parts), but because of the wide variety and wide application, they are counted as one type in actual use, or even referred to as standard parts for short. It usually includes the following 12 types of parts :
1. Bolt: a type of fastener consisting of two parts, a head and a screw (cylinder with external thread), which need to be matched with a nut to fasten and connect two parts with through holes. This type of connection is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection. Commonly used products are hexagon bolts and anchor bolts
2. Stud: There is no head, only a type of fastener with threads on both ends. When connecting, one end of it must be screwed into the part with internal threaded hole, and the other end must pass through the part with through hole, and then screw the nut, even if the two parts are tightly connected as a whole. This type of connection is called a stud connection, which is also a detachable connection. It is mainly used 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. Commonly used products are studs, studs, screw rods, etc.
3. Screw: It is also a type of fastener composed of two parts: head and screw. According to the purpose, it can be divided into three categories: machine screws, set screws and special purpose screws. Machine screws are mainly used for a tightening connection between a part with a threaded hole and a part with a through hole, without the need for nut cooperation (this type of connection is called a screw connection, which is also a detachable connection; It is matched with a nut to fasten the connection between two parts with through holes.) The set screw is mainly used to fix the relative position between the two parts. Special purpose screws such as eyebolts are used for lifting parts. Commonly used products: round knitting screws, flat knitting screws, hexagon socket set screws, and ring screws.
4. Nut: With internal threaded holes, the shape is generally flat hexagonal column, and also flat square column or flat cylinder. It is used with bolts, studs or machine screws to fasten and connect two parts. It becomes a whole. Commonly used products are hexagon nuts, square nuts, welding nuts, etc.
Special categories of nuts
High strength self-locking nut
It is a classification of self-locking nuts with high strength and strong reliability. It is mainly based on the introduction of European technology as a prerequisite for road construction machinery, mining machinery, vibration machinery and equipment, etc. There are very few domestic manufacturers of such products.


Nylon self-locking nut
Nylon self-locking nut is a new type of high anti-vibration and anti-loosening fastening parts, which can be used in various mechanical and electrical products at a temperature of -50~100℃. The demand for nylon self-locking nuts in aerospace, aviation, tanks, mining machinery, automobile transportation machinery, agricultural machinery, textile machinery, electrical products and all kinds of machinery has increased sharply, because its anti-vibration and anti-loose performance is much higher than others Various anti-loose devices, and the vibration life is several times or even dozens of times longer. At present, more than 80% of the accidents of mechanical equipment are caused by the loosening of fasteners, especially in mining machinery. The use of nylon self-locking nuts can prevent major accidents caused by loosening of fasteners.
5. Self-tapping screws: similar to machine screws, but the thread on the screw is a special self-tapping screw thread. It is used to fasten and connect two thin metal components into a whole. Small holes need to be made in the component in advance. Because this kind of screw has high hardness, it can be directly screwed into the hole of the component. Form the corresponding internal thread. This type of connection is also a detachable connection.
6. Wood screw: It is also similar to the machine screw, but the thread on the screw is a special wood screw thread, which can be directly screwed into the wooden component (or part) to use a metal (or non-metal) with a through hole The parts are firmly connected to a wooden component. This connection is also a detachable connection.
7. Washer: A type of fastener with an oblate ring shape. It is placed between the support surface of bolts, screws or nuts and the surface of the connected 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, It can also prevent the nut from loosening.
8. Retaining ring: It is installed in the shaft groove or hole groove of the machine and equipment, and plays a role of preventing the parts on the shaft or hole from moving left and right.
9. Pin: Mainly used for parts positioning, and some are also used for connecting parts, fixing parts, transmitting power or locking other fasteners.
10. Rivet: A type of fastener composed of two parts, a head and a nail shaft, used to fasten and connect two parts (or components) with through holes to make them into a whole. This type of connection is called rivet connection, or riveting for short. Belong to and non-detachable connection. Because to separate the two parts connected together, the rivets on the parts must be broken.
11. Assemblies and connection pairs: Assemblies refer to a type of fastener supplied in combination, such as a combination of machine screws (or bolts, self-supplied screws) and flat washers (or spring washers, lock washers); connection The secondary refers to a type of fastener supplied by a combination of a certain special bolt, nut and washer, such as a high-strength large hexagon head bolt connection pair for steel structures.
12. Welding nail: a heterogeneous fastener consisting of a nail shaft and a nail head (or no nail head), which is fixedly connected to a part (or component) by welding so as to be connected with other parts.