Bolts: Mechanical parts, cylindrical fasteners with threads with nuts. A type of fastener consisting of a head and a screw (a cylinder with external threads) is required to be fitted with a nut to fasten and connect two parts with through holes. This connection form is called bolt connection. If the nut is screwed off from the bolt, the two parts can be separated, so the bolt connection belongs to the removable connection.

There are many names for bolts. Everyone may call them different. Some people call them bolts, some call them bolts, and some call them fasteners. Although there are so many names, but the meaning is the same, are bolts. Bolts are a general term for fasteners. Bolt is a tool for tightening machine parts step by step by step by using the physical and mathematical principles of oblique circular rotation and friction of objects.

Bolts are indispensable in daily life and industrial production. Bolts are also known as industrial rice. It can be seen that bolts are widely used. Bolts are used in electronic products, mechanical products, digital products, electrical equipment, mechanical and electrical products. Bolts are also used in ships, vehicles, water projects and even chemical experiments. Bolts are used in many places anyway. Especially for precision bolts used on digital products. DVD, miniature bolts for cameras, glasses, clocks and watches, electronics, television, electrical products, musical instruments, furniture and other general bolts; for engineering, construction and bridges, large bolts and nuts are used; for transportation equipment, aircraft, trams, automobiles, etc., large bolts and small bolts are used. Bolts play an important role in industry. As long as there is industry on the earth, the function of bolts will always be important.

Generally, the countersunk head is used in the place where the smooth surface of the joints is required, because the countersunk head can be screwed into the parts. The round head can also be screwed into the parts. The tightening force of the square head can be larger, but the size is large. In addition, in order to meet the need of locking after installation, there are holes in the head and in the rod, which can keep the bolt from loosening when it is vibrated. Some bolts have no threaded bars to be thin, called thin waist bolts. This kind of bolt is advantageous to the connection under the variable force. There are special high strength bolts on the steel structure, the head will be bigger, and the size will also change. In addition, there are special uses: T-groove bolts, machine tool fixtures used the most, special shape, head side to be cut off. Ground bolts, which are used to connect the machine to the ground, have many shapes. U-shaped bolts, as mentioned above. Wait. There are special studs for welding, one end with thread and one end without thread, which can be welded on parts, and the other side can be directly screwed nuts.

Ordinary and articulated holes. Ordinary main load bearing axial force, but also can bear the lateral force with low requirements. Bolts for reaming holes should match the dimensions of holes and be used when subjected to transverse forces.

According to the relevant standards, the performance grade of bolts can be divided into more than 10 grades, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, 8.8 and above bolts are made of low-carbon alloy steel or medium-carbon steel and heat-treated (quenched and tempered), commonly referred to as high-strength bolts, and the rest are commonly referred to as ordinary bolts. The grade label of bolt performance consists of two parts, which represent the nominal tensile strength and yield strength ratio of bolt material.