If the hexagonal bolt according to the national standard, its specifications are large and small, such as small M3, M4, M6, etc., such as large can reach M64. At the same time, it is also divided into A and B class hex bolts, if it is A class, it is used for D less than 24 mm. In addition, it can be divided into C-level, of which A-level is the most accurate, and C-level accuracy is the worst. And different precision, different grade representatives, the use will be different. Because the carrying capacity of class A is slightly larger, it is necessary to understand its label when purchasing. If the hexagonal bolt according to the national standard, its specifications are large and small, such as small M3, M4, M6, etc., such as large can reach M64. At the same time, it is also divided into A and B class hex bolts, if it is A class, it is used for D less than 24 mm. In addition, it can be divided into C-level, of which A-level is the most accurate, and C-level accuracy is the worst. And different precision, different grade representatives, the use will be different. Because the carrying capacity of class A is slightly larger, it is necessary to understand its label when purchasing.
If it is divided according to the force mode of the connection, some are ordinary and some are reamed holes, which should be matched with the size of the holes. If it is divided according to the shape of the head, there are some hexagonal heads, some are round or square, and one is countersunk, and the surface is smooth without convex and convex phenomenon, so as to ensure that it can be screwed into the parts. Among them, the hexagonal head is the most commonly used type, some with holes in the head and some with holes in the rod.
Some bolts have no threads, which are called thin waist bolts, and some are used for special purposes, such as T-shaped bolts, which are used for machine tools. Both sides of the head have to be cut off, and some have U-shaped bolts.
If divided according to the bolt performance grade, there are more than 10, of which 3.6, 4.6, 8.8 or more, and some are low-carbon alloy steel or medium carbon steel, which are called high strength. The rest are called ordinary types, mainly because their tensile strength and flexion ratio are not the same. If it reaches the 4.6 level, its tensile strength has exceeded 400MPA.