How to produce M1.2 extended screws？

Release time：2020-01-16 18:44 Browse：

1. Production of M1.2 Extra-Long Screws

1. Material Selection

• Wire Requirements: M1.2 screws typically use high-carbon steel (e.g., 1018, 1022) or stainless steel (e.g., 304, 316) for sufficient strength and corrosion resistance.

• Wire Rod Specification: The initial wire diameter should be slightly larger than the finished screw’s thread diameter (usually 1.4–1.6mm for M1.2).

2. Annealing and Pickling

• Spheroidizing Annealing: High-carbon steel is annealed at 680–715°C to reduce hardness and improve cold-heading plasticity.

• Acid Washing & Phosphating: Removes oxide scales and forms a phosphate coating to facilitate subsequent wire drawing and cold heading.

3. Precision Wire Drawing

• Rough & Fine Drawing: The wire is progressively drawn to near the screw’s shank diameter (~1.2–1.3mm for M1.2) to ensure dimensional accuracy.

• Lubrication: Reduces friction during drawing to prevent surface scratches.

4. Cold Heading (Critical Challenge)

• Special Equipment Adjustments: Due to the tiny size of M1.2 screws, high-precision multi-station cold headers (e.g., DT06102) with optimized die clearance are required.

• Long Shank Processing:

• Multi-Step Heading: The elongated shank requires multiple heading stages to prevent bending or cracking.

• Die Guidance Optimization: Additional guiding structures ensure straightness during forming.

• Head Forming: A two-strike process (pre-forming + final forging) prevents uneven material flow.

5. Thread Rolling

• Precision Dies: High-hardness alloy dies (e.g., SKD11) ensure thread accuracy.

• Low-Speed Rolling: Reduced rolling speed (150,000–200,000 cycles/day) minimizes deformation risks for long screws.

6. Heat Treatment (If Required)

• Carburizing or Quenching & Tempering: Enhances mechanical properties for carbon steel screws.

• Dehydrogenation Baking: If electroplated, bake at 200°C for 8 hours to prevent hydrogen embrittlement.

7. Surface Treatment

• Zinc/Nickel Plating: Improves rust resistance for small screws.

• Dacromet Coating: Used for high-corrosion-resistance applications.

8. Quality Inspection

• Dimensional Checks: Optical measuring instruments verify shank length and thread accuracy.

• Torque Testing: Ensures screws meet specified assembly torque requirements.

Key Challenges & Solutions

1. Shank Straightness: Use closed-die headers or specialized guides to prevent bending.

2. Thread Strength: Optimize rolling parameters to avoid incomplete or damaged threads.

3. Production Efficiency: Lower output (~50,000–80,000/day) requires adjusted production pacing.