Common Manufacturing Processes for Fasteners

1. Annealing
Heating the wire rod to a suitable temperature, holding it there for a specific period, and then cooling it slowly. This process adjusts the crystalline structure, reduces hardness, and improves the wire's workability at room temperature.

2. Pickling
Purpose: To remove the oxide layer from the wire surface and form a thin phosphate coating. This reduces abrasion on tooling and dies during processes such as wire drawing, cold heading, and forming.

3. Cold Heading
Cutting the wire rod and upsetting it into a screw blank. This forms the head, creates the drive recess (e.g., Phillips), and establishes the thread blank diameter, shank length, and the fillet radius beneath the head.

4. Threading
Rolling or tapping the formed semi-finished part to create the required threads. In practice, the process is referred to as "thread rolling" for bolts and screws, "thread rolling" for threaded rods, and "tapping" for nuts.

5. Heat Treatment
Enhancing the screw's strength, hardness, and toughness. A high-quality screw must be neither too hard (which makes it prone to snapping during tightening) nor too soft (which leads to stripped threads or an insecure fit). Heat treatment is essential to achieve a balance of external hardness and internal ductility.

6. Surface Treatment
Surface treatment is the process of applying a coating layer to the workpiece surface. Its purpose is to enhance the product's appearance and provide corrosion resistance.