The production of screws involves a series of precise steps to transform raw metal into durable, threaded fasteners. Below is a detailed overview of the key stages:
1. Wire Drawing
The process begins with wire drawing, where coiled metal wire (carbon steel, stainless steel, etc.) is pulled through a series of progressively smaller dies to reduce its diameter and enhance tensile strength. Lubricants are applied to minimize friction and prevent surface damage.
2. Cold Heading
In cold heading, the drawn wire is cut into blanks and shaped into screw heads at room temperature using high-pressure dies and punches. Our one die two blow screw cold heading machine forces the wire into a die cavity, forming the head (e.g., hexagonal, pan, or flat head) through two strikes. This cold-working process increases metal density and strength. Annealing may precede cold heading if the wire is too brittle, improving ductility.
3. Thread Rolling
Threads are created via thread rolling, a cold-forming process. The screw blank is pressed between two grooved dies, displacing metal to form precise threads without cutting. This method preserves the grain structure, enhancing thread strength and fatigue resistance compared to machined threads. The rolled threads also have a smoother surface, reducing friction during installation.
4. Heat Treatment
For high-strength screws (e.g., Grade 8 or 12.9), heat treatment is critical. The screws are heated to austenitizing temperatures, quenched in oil or water to achieve high hardness, and then tempered to reduce brittleness while maintaining toughness. Stress-relieving may follow to eliminate internal stresses from prior forming steps.
5. Surface Treatment
To prevent corrosion, screws undergo surface treatments such as electroplating (zinc, nickel), hot-dip galvanizing, phosphating, or coating. These layers also improve aesthetics and friction properties. Passivation might be applied to stainless steel screws to enhance oxide layer integrity.
This demonstrates that subsequent processing relies on the precision of cold-headed blanks. Even under high-speed continuous operation, our one die two blow screw cold heading machine consistently ensures the accuracy of each blank, delivering exceptional results that meet customer expectations.
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