The forming of the bolt head adopts cold heading plastic processing. Compared with cutting processing, the metal fiber (metal wire) is continuous along the product shape without cutting in the middle, thus improving the product strength, especially the excellent mechanical properties. The cold heading forming process includes cutting and forming, single station single click, double click cold heading, and multi station automatic cold heading. An automatic cold heading machine performs multi station processes such as stamping, upsetting, extrusion, and diameter reduction in several forming dies. The processing characteristics of the original blank used in single or multi station automatic cold heading machines are determined by the size of the material, which is 5-6 meters long, or 1900-2000KG weight of wire rod steel wire. The characteristic of the processing technology is that cold heading forming does not use pre cut single blanks, but uses the automatic cold heading machine itself to cut and thicken (if necessary) the blank from the bar material and wire rod steel wire. Before extruding the cavity, the blank must be shaped. Through plastic surgery, a blank that meets the process requirements can be obtained. Before forging, reducing diameter, and positive extrusion, the blank does not need to be shaped. After cutting the blank, it is sent to the upsetting and shaping station. This workstation can improve the quality of the blank, reduce the forming force of the next workstation by 15-17%, and extend the life of the mold. Multiple diameter reductions can be used to manufacture bolts.

1. The simplest method to cut the blank with a semi enclosed cutting tool is to use a sleeve type cutting tool; The angle of the incision should not exceed 3 degrees; When using an open cutting tool, the angle of the cut can reach 5-7 degrees.

2. During the process of transferring small-sized blanks from the previous workstation to the next forming workstation, they should be able to flip 180 degrees, which can unleash the potential of automatic cold heading machines to process complex fasteners and improve part accuracy.

3. Punch discharge devices should be installed at each molding station, and concave molds should be equipped with sleeve type top feeding devices.

4. The number of forming stations (excluding cutting stations) should generally reach 3-4 stations (in special cases, more than 5 stations).

5. During the effective use period, the structure of the main slider guide rail and process components can ensure the positioning accuracy of the punch and die.

6. Terminal limit switches must be installed on the baffle for controlling material selection, and attention must be paid to controlling the forging force.

The out of roundness of the cold drawn wire used for manufacturing high-strength fasteners on automatic cold heading machines should be within the diameter tolerance range, while for more precise fasteners, the out of roundness of the wire should be limited to 1/2 diameter tolerance range. If the wire diameter does not reach the specified size, cracks or burrs will appear on the upsetting or head of the part. If the diameter is smaller than the required size of the process, the head will be incomplete, and the edges or bulges will be unclear. The accuracy that can be achieved by cold heading forming is also related to the selection of forming methods and the processes used. In addition, it also depends on the structural characteristics of the equipment used, the process characteristics and their status, the precision of the tools and molds, their lifespan, and the degree of wear and tear. The working surface roughness of high alloy steel and hard alloy molds used for cold heading and extrusion should not be too large, Ra=0.2um. When the roughness of the working surface of such molds reaches Ra=0.025-0.050um, they have the highest service life.