The so-called hexagon socket bolt refers to a cylindrical head with a hexagon socket shape, and can also be called a hexagon socket screw. Commonly used hexagon socket bolts are 4.8, 8.8, 10.9 and 12.9. We can choose different grades of hexagon bolts according to the different needs of customers, so that the performance of the bolts can play a more beneficial role. According to the understanding of China Standard Parts Network, tell you what are the hardness of the hexagonal bolts.

Hardness grade of Hexagon Socket Head Bolt （https://www.chinaweigao.com/product/bolt/hexagon-socket-head-bolt.html）
Hexagon bolts are classified according to the hardness, bearing capacity, and yield strength of the thread, that is, the grade of the hex bolt and what grade is the hex bolt. Different products and materials require different grades of hexagon socket bolts. All hexagon socket bolts have the following grades:
Hexagon socket bolts are divided into ordinary bolts and high-strength bolts according to their strength grades. Ordinary hexagon bolts are grade 4.8, and high-strength hexagon bolts are grade 8.8 and above, including grade 10.9 and grade 12.9. Class 12.9 hexagon socket head bolts generally refer to natural oily black hexagon socket head screws with rollers.
There are more than 10 grades of hexagon socket bolts for steel structure connection such as 3.6, 4.6, 4.8, 5.6, 6.8, 9.8, 10.9, and 12.9. Among them, the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel. After heat treatment (quenched and tempered), they are generally called high-strength bolts, and the rest are generally called ordinary bolts. The bolt performance grade is composed of two parts, which respectively represent the nominal tensile strength value and the bending strength ratio of the bolt material.

Performance level
The bolt performance grade is composed of two parts, which respectively represent the ratio of the nominal tensile strength value and the bending strength of the bolt material. For example, for a bolt with a performance level of 4.6, its meaning is:
1. The nominal tensile strength of the bolt can reach 400MPa;
2. The flexural strength ratio of the bolt material is 0.6; the nominal yield strength of the bolt material is 400×0.6=240MPa.
Performance grade 10.9 high-strength bolts, after heat treatment, the material can reach:
1. The nominal tensile strength of bolts can reach 1000MPa;
2. The flexural strength ratio of the bolt material is 0.9; the nominal yield strength of the bolt material is 1000×0.9=900MPa.
The meaning of the performance level of hexagon socket bolts is the international general standard. The performance of the bolts of the same performance level is the same regardless of the material and origin. You only need to select the performance level in the design.
The grades of hexagon socket bolts are basically the same, and the prices of grades must be different in the market. The price of general high-strength hexagon socket bolts is definitely higher than that of ordinary hexagon socket bolts. There are also four grades on the market: 4.8, 8.8, 10.9 and 12.9.

China Stud Supplier ( https://www.chinaweigao.com/) Introduction Advantages of using hexagon socket bolts
1. Can withstand larger loads. It has six load-bearing surfaces, which can withstand more than flat-blade screws and Phillips screws on both sides.
2. The hexagonal bolts in use can be countersunk, that is, the whole nut sinks into the inside of the workpiece, which can keep the surface of the workpiece smooth and beautiful.
3. Easy to install.
Compared with the hexagonal screws, the hexagonal screws are suitable for more assembly occasions, especially the narrow ones, so the assembly and maintenance are very convenient, and the debugging is also convenient.
4. It is not easy to disassemble.
The tools we usually use are adjustable wrenches, screwdrivers and wrenches, and special wrenches must be used to remove hexagon bolts. Therefore, it is not easy for ordinary people to disassemble, which is also a benefit. Of course, if you work hard, you can design a variety of weird structures. The problem is that special wrenches are not easy to manufacture.