What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
According to the force of the connection, it is divided into ordinary and hinged holes. According to the shape of the head: there are hexagonal head, round head, square head, countersunk head and so on. Among them, the hexagonal head is the most commonly used. Generally, countersunk heads are used where connections are required. [1] The English name of the riding bolt is U-bolt. It is a non-standard part. The shape is U-shaped, so it is also called a U-bolt. There are threads on both ends that can be combined with nuts. It is mainly used to fix tubular objects such as water pipes or sheets such as The leaf spring of a car is called a horse-riding bolt because it fixes the object in the same way that a person rides on a horse. According to the length of the thread, it is divided into two categories: full thread and non-full thread. [2] According to the thread type, it is divided into two types: coarse thread and fine thread. The coarse thread is not displayed in the bolt mark. The bolts are divided into eight grades: 3.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9 according to their performance grades. Among them, the bolts above grade 8.8 (including grade 8.8) are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched). + Tempering), commonly known as high-strength bolts, and below grade 8.8 (excluding 8.8) are commonly known as ordinary bolts. [2] Ordinary bolts can be divided into three grades: A, B, and C according to the production accuracy. Grades A and B are refined bolts, and grade C is rough bolts. For connecting bolts for steel structures, unless otherwise specified, they are generally ordinary rough grade C bolts. There are differences in the processing methods of different grades. Usually the corresponding processing methods are as follows: ① The bolts of grade A and B bolts are processed by lathes, with smooth surfaces and accurate dimensions. High, rarely used; ②C-grade bolts are made of unmachined round steel, the size is not accurate enough, and its material property grade is 4.6 or 4.8. The deformation is large during shear connection, but the installation is convenient and the production cost is low. It is mostly used for tensile connection or temporary fixation during installation. [2]
The force condition of the screw is broadcasted: 1) Self-weight G; 2) Torque M required to overcome material resistance; 3) Axial force P generated by material pressure. Screw screw screw is generally scrapped due to long-term wear, the gap between the screw and the barrel is too large and cannot be extruded normally, but there are also examples of damage due to improper design or improper operation. Therefore, the screw should also meet certain strength requirements. 4) The dangerous section of the screw is generally at the smallest thread root diameter in the feeding section. According to material mechanics, for plastic materials, the composite stress is calculated by the third strength theory, and its strength conditions are:
Fasteners are also divided into different types according to different uses, and new types of fasteners are developed according to the needs of special environments to meet the needs of all walks of life. The gasket combination bolt is a common fastening bolt. The combination gasket protects the surface of the connected parts from scratches, disperses the pressure on the connected parts, and has a sealing and anti-loosening effect. It is widely used. With the continuous improvement of requirements, the new zinc-aluminum coating surface treatment has gradually become the mainstream surface treatment process because it meets the environmental protection requirements, the surface is beautiful, and the corrosion resistance strength is higher than that of the zinc-nickel surface treatment.
Nut fasteners are used in various industries with connection and fastening requirements, such as vehicles, construction machinery, agricultural machinery, manufacturing machinery, etc. For large construction machinery or construction vehicles, due to the harsh working environment and the action of heavy loads, the nut fasteners on it are subjected to vibration and load impact in all directions, which makes the nut easier to loosen, resulting in tightening. The function of the device is reduced or even failed. cause a great safety hazard.
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