The Stainless Steel Countersunk Socket Screw (also known as a stainless flat head socket screw or DIN 7991 Allen screw) is a high-precision, corrosion-resistant fastener designed for flush surface mounting in space-restricted, sanitary, and harsh atmospheric environments. Engineered with a 90-degree conical countersunk head and deep internal hex drive from premium austenitic stainless steel grades (SS304 / A2-70 and SS316 / A4-80), this fastener delivers smooth aesthetic integration and self-healing corrosion protection in accordance with global ISO standards.
Technical Specifications of Stainless Steel Countersunk Socket Screw
Austenitic stainless steel property classes provide high tensile endurance without rusting or magnetizing. Grade A2-70 (SS304) offers a minimum tensile strength of 700 MPa for general machinery, medical, and food processing applications. Grade A4-80 (SS316) includes 2-3% Molybdenum content to achieve 800 MPa tensile strength while resisting harsh chloride pitting in marine and chemical processing environments.
| Grade Marking | Stainless Material Grade | Tensile Strength (Min) | Head Angle / Feature | Corrosion Environment |
|---|---|---|---|---|
| A2-50 / A2-70 | AISI 304 / SS304 (1.4301 / 06Cr19Ni10) | 500 – 700 N/mm² (700 MPa) | 90° Conical Countersunk Head | Freshwater, General Outdoor & Food Industry |
| A4-70 / A4-80 | AISI 316 / SS316 (1.4401 / 06Cr17Ni12Mo2) | 700 – 800 N/mm² (800 MPa) | 90° Conical Countersunk Head | Marine Coastal, Salt Spray & Chemical Processing |
Cold Heading and Passivation Process for Stainless Steel Countersunk Socket Screw
At our specialized manufacturing facility in Handan, China, stainless steel flat head socket screws undergo multi-stage cold forming and chemical surface treatment to ensure precision head alignment and smooth assembly:
- Conical Head & Internal Hex Cold Extrusion: High-speed multi-station formers cold-extrude the precise 90-degree countersunk head and deep internal hex socket to prevent key rounding under high driving torque.
- High-Precision Thread Rolling: Metric 6g threads are rolled to achieve smooth pitch concentricity and surface finish, drastically minimizing thread galling or seizing in stainless tapped holes.
- Acid Pickling & Chemical Passivation: Chemical washing removes microscopic iron contaminants left by tooling, allowing a pure chromium oxide passive film to regenerate across all surfaces.
- Optional Anti-Galling Lubrication: Dry-wax or PTFE anti-seize coatings can be applied upon request to facilitate high-speed automated power assembly.
Flush Surface Applications of Stainless Steel Countersunk Socket Screw
The completely flat, protrusion-free surface appearance makes stainless steel countersunk socket screws ideal for applications with moving clearance requirements or high aesthetic standards:
- Automation & CNC Machine Tools: Fastening linear guide rails, slide plates, and machine guard panels where zero head obstruction is required.
- Food, Beverage & Medical Machinery: Assembling sanitary processing line covers, conveyor guide plates, and laboratory equipment requiring frequent washdowns.
- Marine Hardware & Architectural Fittings: Securing boat deck plates, coastal glass railing brackets, and outdoor stainless steel architectural panels using SS316 (A4-80).
Quality Assurance and Export Packaging for Stainless Steel Countersunk Socket Screw
Handan YiHao Fastener enforces strict Quality Control (QC) protocols for all export orders. Inspection procedures include Positive Material Identification (PMI) chemical spectro-analysis for Nickel and Chromium content, 90° head angle measurement, internal hex socket depth gauge testing, and thread ring gauge checks.
All export items are packed in heavy-duty 25kg inner cartons, neatly stacked on ISPM 15 compliant fumigated wooden pallets, and wrapped in protective stretch film for safe ocean transport.
Request Factory Direct Pricing for Stainless Steel Countersunk Socket Screws
Looking for a trusted manufacturer in Handan, China for SS304 (A2-70) or SS316 (A4-80) stainless steel countersunk socket screws (DIN 7991)? Contact Handan YiHao Fastener today for technical datasheets, CAD drawings, sample shipments, and direct bulk export quotes.
