The nut manufacturing process mainly includes cold heading, tapping, heat treatment, and surface treatment. Cold heading is the core step, suitable for mass production, effectively improving material utilization and ensuring precision.
The main production process flow is as follows:
Raw Material Preparation: Materials such as carbon steel, alloy steel, stainless steel, or copper are typically used. Raw materials are mostly wire or bar stock, and it is necessary to ensure that the material meets standards to satisfy strength and corrosion resistance requirements.
Cold Heading (Blank Forming): At room temperature, metal wire is subjected to high-speed stamping using a cold heading machine, completing the cutting, heading, and forming processes in one step to form a hexagonal nut blank. This process achieves a material utilization rate of 80%–90% and high production efficiency, reaching hundreds of pieces per minute.
Tapping (Internal Thread Machining): An internal thread is machined into the hole of the nut blank using a tapping machine. For hot-forged nuts, an automated tapping machine is used to ensure thread finish and precision.
Heat Treatment: High-strength nuts undergo heat treatment, involving heating, holding, and cooling to enhance hardness and toughness, thereby improving their mechanical properties. For example, bolts and nuts of M10 and above, or grade 8.8 and above, typically require heat treatment.
Surface Treatment: To improve corrosion resistance and appearance, common treatments include galvanizing (e.g., blue-white zinc, color zinc), blackening, nickel plating, or Dacromet coating. Different surface treatment methods are selected for different application environments.
Special Process Supplements:
Hot Forging Nuts: Suitable for large-size nuts. They are first heated, then forged, and finally tapped.
Nut Embedding: Copper nuts are embedded into plastic parts using methods such as hot melting or ultrasonic welding. Widely used in the manufacture of electronic device housings.
Automated Insertion: Nut embedding machines enable precise positioning and batch processing, improving production efficiency and consistency.
