The following is a detailed description of the custom requirements for US-standard 6-32 die-formed electrophoretic black high-salt spray straight knurled cross-recessed cold-forged thumb screws. The content is organized by technical key points, balancing professionalism and operability.'
1. Basic Parameters and Standards
Thread Specification: US-standard 6-32 UNC, compliant with ANSI/ASME B18.6.3.
Head Type: Thumb-screw design, with straight knurling to ensure anti-slip properties.
Groove Type: Cross-recessed under ISO 7046, groove number #2, with a depth that fully matches a standard Phillips screwdriver.
2. Material and Process Requirements
Material: Low-carbon alloy steel, tensile strength ≥8.8, surface hardness HRC 22-32.
Cold Forging: Processed on a multi-station cold forging machine, the head and threads are formed simultaneously to avoid fiber shearing caused by turning and ensure mechanical strength.
Heat Treatment: Tempering treatment to eliminate internal stresses and ensure the core and surface hardness gradient is ≤ HRC 5.
3. Surface Treatment Specifications
Electrophoretic Black Coating: Film thickness 8-12μm, salt spray test ≥ 500 hours (passes neutral salt spray test, no red rust).
Electrophoretic Paint Type: Epoxy resin-based, color RAL 9005, gloss ≤ 10%, matte finish required.
Straight Knurl Protection: Slight coating thinning is permitted at the top of the knurl after electrophoresis, but the base material must not be exposed. 100% visual inspection is required.
4. Key Dimensions and Tolerances
Overall Length: As per customer drawing (unless otherwise specified, 1/2" to 2" is the default option). Length tolerance ±0.1mm.
Knurl Outer Diameter: Nominal diameter + 0.3mm, ovality ≤ 0.05mm.
Cross Slot Concentricity: Deviation from the screw axis ≤ 0.1mm.
5. Special Performance Verification
Torque Test: Installation torque ≥ 3.5 N·m (cross groove anti-slip), breakaway torque ≥ 8 N·m; knurling torque ≥ 1.2 N·m.
Post-Salt Spray Adhesion: Cross-hatch test, electrophoretic coating peeling area ≤ 5%.
6. Packaging and Labeling
Packaging: Anti-rust paper + vacuum bag, outer box humidity card indicates <30% RH.
Labeling Requirements: Laser-mark the batch number on the side of the head, font height 0.8mm, do not abrade the electrophoretic coating.
7. Custom Process Nodes
Mold Development: Provide 3D drawings to confirm the transition radius between the knurl and the head (to avoid stress concentration).
First Sample Inspection: Submit 30 samples, full-size CMM report + salt spray test data.
Mass Production Control: Randomly inspect 5 units every 2 hours, key dimensions CPK ≥ 1.33.
Notes
Material Substitution: If stainless steel is required, the cold heading deformation rate must be recalculated and the die clearance adjusted.
Environmental Compliance: Electrophoretic paint requires a RoHS/REACH test report, and heavy metal content must meet environmental standards.
Only by meeting these detailed requirements can screws ensure both functionality and durability in harsh environments such as electronic equipment and outdoor equipment. It is recommended to sign a technical agreement with the manufacturer to clearly define acceptance criteria.
