External hexagonal screws with a collar and washer step are multifunctional fasteners. Below is a detailed explanation of their customization requirements, taking into account key parameters and production considerations.
I. Core Specifications
Thread Specifications
Metric coarse threads: M3, M4, M5, and M6. Fine threads are optional and must be specified. Machine thread direction must be specified (right-hand thread is the default).
Head and Drive
External hexagonal head: Across-flat dimensions are standard (e.g., M6 corresponds to 10mm) or custom thickened.
Ledger (flange) design: The flange face diameter must be larger than a standard hexagonal head to provide a larger contact surface.
Integrated step and washer
Step height: Typically 1-2 times the thread diameter (e.g., an M5 step height of 5-10mm).
Washer type: Flat washer/spring washer, molded in one piece, made of the same material as the screw (spring washer required for anti-loosening).
Anti-slip and Gluing Process
Anti-slip nylon: A nylon rubber ring is pre-placed in the middle of the thread, temperature resistant from -40°C to 120°C.
Secondary Gluing: Epoxy resin glue is applied to the end of the thread to prevent loosening after curing.
II. Materials and Processing
Conventional: Carbon steel (grade 4.8/8.8/12.9), stainless steel (A2-70/A4-80).
High-strength: Alloy steel (such as SCM435) or titanium alloy (for aviation applications).
Surface Treatment
Corrosion Protection: Galvanizing (blue-white/colored zinc), Dacromet, nickel plating.
Wear Resistance: Black Oxide, DLC Coating.
III. Key Tolerances and Inspection
Dimensional Tolerance: Threads are 6g grade, step diameter ±0.05mm.
Performance Testing
Includes torque testing and salt spray testing.
IV. Key Points in the Customization Process
Drawing Confirmation: 3D drawings or key dimensions must be provided.
Prototype Phase: Samples are produced within 3-5 working days to verify the adhesive retention.
Mass Delivery Time: 15-20 days.
V. Common Problems Avoidance
Anti-drop failure: Avoid using an excessively shallow nylon rubber ring (recommended embedment depth ≥ 0.3mm).
Washer cracking: Control the cold heading process parameters during one-piece molding.
Uneven dispensing: Utilize high-precision dispensing equipment with a dispensing tolerance of ±0.01g.
Through its integrated structure and upgraded anti-loosening technology, this screw eliminates the loosening problem of traditional screws in vibrating environments, while improving assembly efficiency and reliability. It is an ideal fastening solution for precision industrial applications.
