Principles, deformation modes, and permissible degrees of deformation for cold heading and cold pressing processes.
Jun 08, 2026
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Cold heading and cold pressing are core room-temperature forming processes used in the production of fasteners and precision hardware components, where the shaping of the workpiece occurs entirely at ambient temperature; self-clinching screws, for instance, are predominantly mass-produced using these established techniques. The process involves placing a metal blank into a specialized die and using the power of cold heading machines or presses to drive the relative movement of the upper and lower dies. This forces the blank to undergo plastic deformation within the die cavity-reducing its height while increasing its cross-sectional area-making it a key process for the efficient mass production of precision fasteners.
In actual industrial production, the cold forming of fasteners does not rely on a single process; the formation of self-clinching bolts, for example, integrates the characteristics of both cold heading and extrusion. Conventional cold heading operations often incorporate extrusion techniques to achieve higher dimensional accuracy and a denser internal structure. Consequently, fastener cold heading is considered a composite forming process that combines the rapid shaping capabilities of cold heading with the precision forming advantages of extrusion.
Blanking is a fundamental pre-processing deformation method in cold heading and is widely used in the manufacture of various self-clinching fasteners; for instance, the blank shaping of self-clinching compression screws relies on this process. Its core function is to completely separate a specific section of the blank from the main body. Common applications include cutting raw wire stock, pre-punching holes in nuts, and trimming bolt heads, thereby establishing a uniform blank foundation for subsequent precision heading and shaping.
Upsetting is the core process in cold heading, primarily used to optimize the structural dimensions of the blank; the head formation of clinching screws typically employs this technique. The process involves using a die to apply pressure, thereby reducing the blank's height and increasing its cross-sectional area. It is essential for key steps such as spherical upsetting for nuts and the pre-heading and finish-heading of bolt heads, effectively enhancing the workpiece's structural density and ensuring the fastener's structural integrity after forming.
Forward extrusion is a vital method for precision cold heading and is suitable for processing the shanks of various precision screws; the shank diameter reduction of push-in clinching screws, for example, often utilizes this process. During machining, the metal flows in the same direction as the upper die's movement. This method is frequently used for shank reduction and diameter narrowing on bolts and hex socket screws, allowing for precise control of dimensional tolerances and improved assembly fit.
Backward extrusion operates with a metal flow logic opposite to that of forward extrusion and is commonly used to form complex fastener geometries; the head formation of Revtex® self-clinching screws, for instance, relies on this process. During shaping, the metal flows in the opposite direction to the die's movement. Primarily applied to processes such as forming the heads of cylindrical hex socket screws and deep drawing, it enables the efficient, integrated forming of complex, non-standard shapes.
Combined extrusion is a core forming process for high-end precision fasteners, integrating the advantages of both forward and backward extrusion; the integrated forming of self-clinching studs often employs this combined process. At a single processing station, the workpiece undergoes simultaneous forward and backward metal flow-with some metal flowing forward with the die to reduce the diameter of the shaft section, while other metal flows backward to shape the head-thereby achieving multi-feature forming in one operation and significantly enhancing both production efficiency and product precision.
Cold heading processes involve specific processing thresholds-namely, the permissible degree of metal deformation-that directly impact finished product yields and die longevity; consequently, the mass production of self-clinching threaded fasteners requires strict adherence to deformation standards. If the cold heading deformation exceeds the metal's plastic limit, defects such as cracking or wrinkling appear on the workpiece sides, resulting in high volumes of defective parts and accelerated die wear-or even catastrophic die failure due to cracking.
The plasticity of the metal material directly determines the permissible deformation level and plays a decisive role in the cold heading process; therefore, material selection for threaded clinching screws must align with the corresponding deformation parameters. Metals with superior plasticity can withstand greater cold heading deformation and offer higher processing tolerance. Conversely, for carbon steels, plasticity declines as carbon content rises, leading to a corresponding reduction in permissible deformation and a heightened risk of cracking during processing.
For materials with lower plasticity, such as medium-carbon steel and alloy steel, the industry has developed mature cold heading optimization strategies to ensure stable mass production of various self-clinching fasteners; processing hard materials for self-clinching mounting screws necessitates specific pre-treatments. Common production measures-such as annealing to soften the steel, optimizing die toughness, and enhancing blank surface lubrication-are employed to effectively increase the permissible metal deformation and prevent issues like workpiece cracking and die damage.
Overall, the combined cold heading and cold pressing process has become the mainstream manufacturing method for self-clinching mounting screws, thanks to its advantages of high efficiency, precision, and integrated forming. The process encompasses five core deformation modes-blanking, upsetting, forward extrusion, backward extrusion, and combined extrusion-to meet the forming requirements of workpieces with diverse structural designs. Furthermore, strictly controlling the permissible degree of metal deformation and optimizing the process based on material characteristics are crucial for improving product yield, reducing production costs, and extending die life; this holds significant value for the precision fastener manufacturing industry.
Please feel free to contact us for information on process parameter adjustment, material compatibility solutions, and techniques for controlling deformation, and to receive professional technical guidance on precision hardware forming processes.
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