Bolt manufacturers introduce you to the classification of bolts


Bolt manufacturers introduce you to the classification of bolts

According to the bearing capacity of the connection, the bolt manufacturers can be divided into general ones and those with reaming holes. According to the shape of the head: there are hexagonal head, square mouth, square head, and countersunk head. Among them, the hex head is the most common. Generally, the countersunk head is used in the area where connection is required. 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 sides that can be combined with the nut. It is mainly used to fix tubular substances such as water pipes or small objects such as leaf springs. According to the thread length, it is divided into two types: full thread and part-time thread. Bolt manufacturers are divided into two types: coarse thread and fine thread according to the thread of the thread, and the coarse thread cannot be displayed in the logo of the bolt. Bolts are divided into eight grades according to performance grades: Among them, bolts above grade 8.8 (including grade 8.8) are made of environmentally friendly alloy steel or high-carbon steel and heat-treated (heat treatment process + heat treatment). They are commonly called high-wear bolts, and grades below 8.8 (without grade 8.8) are commonly called ordinary bolts. General bolts can be divided into three grades of A.B.C according to the manufacturing accuracy, A.B grade is specially made bolts, and C grade is made of random bolts. As for the connecting bolts used in the steel frame, unless they are specially marked, they are generally ordinary C-grade bolts. There are differences in the production and processing methods of different grades of bolt manufacturers, which generally conform to the following manufacturing methods: ①The bolts of A and B grade bolts are processed by CNC lathes, with smooth surfaces and accurate specifications. The deformation is large when the bending strength is connected, but the installation is convenient and quick, and the production and processing costs are low. It is mostly used for tensile strength connection or temporary fixation during installation.

Bolt manufacturers introduce you to the method of screwing bolts

Recently, I have been promoting the spirit of craftsman, reporting how careful and meticulous the way German bolt manufacturers tighten bolts is, and how to compare it with the way Chinese workers tighten bolts. Strictly speaking, in the process of equipment installation, the bolt tightening method has already been stipulated in the formulation, and even which tool is defined? Regarding the matter of tightening the bolts, what method is used to tighten them? What steps must be followed for tightening? It is not determined by the installer himself, but defined by the designer. What kind of tools should be used? How to operate? All are industry standards. So the question is, how to set an operation specification for such a simple matter as screwing the bolts? Do interior designers really pick faults? In fact, screwing the bolts is not as simple as imagined. The purpose of screwing the bolts is to obtain an original pre-tightening force of the bolts. What is the role of this torque? Why should the bolt get an original pre-tightening force? This starts with the function of the bolt connection. 01 Transmission of lateral force or torque bolt pre-tightening force creates pressure in the middle of the surface of the connected part. The greater the pressure in the middle of the surface, the greater the lateral force that can be transmitted. When the working pressure on the surface is very high, all the lateral force is transmitted by the sliding friction force. The bolt only bears the pretightening force and will not be subjected to shear stress and ground stress. The stability of the bolt is increased a lot. Once a gap is formed in the middle of the connected parts, the bolt tension will increase rapidly with the increase of the external tension load. The figure below shows the trend diagram of the bolt tension and external load. We can see that in the upper half of the line, the middle of the connected parts has not yet been opened, and the bolt tension increases slowly. After the connected parts are opened, the bolt tension increases rapidly. After the joints are opened, the alternating fatigue load amplitude value of the bolt will also increase rapidly, which will greatly shorten the fatigue limit of the bolt.

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