Drill holes according to the diameter of the inner hexagon to meet the requirements.

Use a cold heading machine to upset the hexagonal socket screws. A single piece can be punched with a hexagonal punch and hammered out. Similar to countersunk screws, the head of the screw is embedded in the machine and has a high connection strength, but the screw must be installed and removed using a corresponding hexagonal wrench. Generally used on various machine tools and their accessories.

The performance grades of internal hexagonal bolts used for steel structure connection are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, bolts of grade 8.8 and above 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 referred to as ordinary bolts. The bolt performance grade label consists of two parts of numbers, representing the nominal tensile strength value and yield strength ratio of the bolt material.