Bolts: mechanical parts, cylindrical threaded fasteners with nuts. A type of fastener consisting of a head and a screw (cylinder with external thread), which needs 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.

According to the force mode of the connection, it is divided into ordinary and reamed hole. 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. The countersunk head is generally used where connection is required.

According to the thread length, it is divided into two types: full thread and non-full thread.

According to the thread type, it is divided into two types: coarse thread and fine thread. The coarse thread type is not displayed in the bolt mark.

Bolts are divided into eight grades of 3.6, 4.8, 5.6, 5.8, 8.8, 9.8, 10.9, 12.9 according to their performance grades. Among them, bolts of grade 8.8 and above (including grade 8.8) are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched). + Tempering), generally referred to as high-strength bolts, generally referred to as ordinary bolts below grade 8.8 (excluding grade 8.8).

Ordinary bolts can be divided into three grades of A, B, and C according to the manufacturing accuracy. Grades A and B are refined bolts, and grade C is coarse bolts. For connecting bolts for steel structures, unless otherwise specified, they are generally ordinary crude grade C bolts. ①The bolts of grade A and B bolts are processed by lathes, with smooth surface and precise size. The material performance grade is 8.8, the production and installation are complicated, and the price is relatively high, so it is rarely used; ②The grade C bolts are made of unprocessed round steel. The size is not accurate enough, and the material performance level is 4.6 or 4.8. Large deformation during shear connection, but convenient installation and low production cost, it is mostly used for tensile connection or temporary fixation during installation.

　　 There are many names for bolts, and everyone may call it differently. Some people call it screws, some people call it bolts, some people call it standard parts, and some people call it fasteners. Although there are so many names, they all mean the same thing. They are all bolts.

　　 Bolt is a general term for fasteners. The principle of the bolt is to use the physics and mathematics principle of the oblique circular rotation of the object and the friction force to gradually tighten the utensils.

　　 Bolts are indispensable in daily life and industrial production. Bolts are also called the rice of industry. It can be seen that the bolts are widely used. The application range of bolts are: electronic products, mechanical products, digital products, electrical equipment, electromechanical products. Bolts are also useful in ships, vehicles, water conservancy projects, and even chemical experiments. Anyway, bolts are used in many places. Such as precision bolts used on digital products. Miniature bolts used in DVDs, cameras, glasses, watches, electronics, etc.; general bolts for televisions, electrical products, musical instruments, furniture, etc.; as for engineering, construction, and bridges, large bolts and nuts are used; transportation equipment, airplanes, trams, and automobiles And so on, are used for both large and small bolts. Bolts have important tasks in industry. As long as industry exists on the earth, the function of bolts will always be important.

Generally, the countersunk head is used where the surface after connection is required to be smooth and without protrusions, because the countersunk head can be screwed into the part. The round head can also be screwed into the part. The tightening force of the square head can be larger, but the size is large.

In addition, in order to meet the needs of locking after installation, there are holes on the head and holes on the rod. These holes can prevent the bolt from loosening when it is vibrated.

Some bolts are not threaded smooth rods to be thin, called thin waist bolts. This kind of bolt is conducive to the connection under variable force.

There are special high-strength bolts on the steel structure, the head will be larger and the size will also change.

In addition, there are special uses: T-slot bolts, the most used on machine tool fixtures, special shapes, and both sides of the head should be cut off. Anchor bolts are used to connect and fix the machine and the ground. There are many shapes. U-shaped bolts, as mentioned above. and many more.

There are also special studs for welding. One end has a thread and the other is not. It can be welded to the part and the nut is directly screwed on the other side.

Cold forging machines currently include one-die two-punch, two-die two-punch, two-die three-punch, two-die four-punch, three-die three-punch, open and close die, etc., to make all kinds of screw products, such as woodworking screws, self-tapping screws, Fiberboard nails, drywall screws, various rivets, axle parts, etc., from simple types to various types with complex structures-the head and handle can be formed by a cold heading machine.