Product Overview
DIN 7991 hex socket countersunk head screws are precision fasteners designed for flush mounting, offering secure torque control for industrial and automotive assemblies, robotics, and sheet metal structures.
Technical Specifications
| Parameter | Specification |
| Diameter Range | 3 mm – 12 mm |
| Length Range | 6 mm – 100 mm |
| Head Type | Countersunk flat head (90°) |
| Drive Type | Internal hex socket (Allen) |
| Hex Socket Size | ISO-matched |
| Thread Type | Metric thread, fully threaded (standard), partial thread optional |
| Material | Carbon Steel / Stainless Steel / Alloy Steel |
| Grade | Carbon Steel: 8.8 / 10.9 / 12.9 Stainless Steel: A2-70 / A4-70 / A4-80 |
| Tensile Strength | 800–1220 MPa (depending on grade) |
| Hardness | HRC 28–42 (depending on grade) |
| Surface Finishes | Zinc Plating, Black Oxide, Mechanical Galvanizing, Plain Stainless |
| Standards Compliance | DIN 7991 / ISO 10642 |
| Custom Options | Custom sizes and materials available on request |
Dimensions & Drive
| Nominal Diameter (d) | M3 | M4 | M5 | M6 | M8 | M10 | M12 |
| Thread Pitch (mm) | 0.5 | 0.7 | 0.8 | 1 | 1.25 | 1.5 | 1.75 |
| Head Diameter (d₁ max, mm) | 6 | 8 | 10 | 12 | 16 | 20 | 24 |
| Head Height (k max, mm) | 1.7 | 2.3 | 2.8 | 3.3 | 4.4 | 5.5 | 6.5 |
| Hex Socket Size (s, mm) | 2 | 2.5 | 3 | 4 | 5 | 6 | 8 |
Standards & Equivalents
DIN 7991 (German Standard)
ISO 10642 (International Standard)
BS EN ISO 10642 (European/UK Standard)
UNI 5933 (Italian Standard)
Manufacturing Process
Cold Heading: Forms the screw blank with precise dimensions.
Thread Rolling: Produces high-precision metric threads.
Heat Treatment: Applied for high-strength grades (8.8, 10.9, 12.9) to achieve required tensile properties.
Surface Finishing: Zinc plating, black oxide, or mechanical galvanizing applied as specified.
Dimensional Control: In-process measurement ensures all screws meet strict DIN 7991 tolerances.
Applications
Industrial machinery assemblies
Automotive components and structural fixtures
Robotics and automation systems
Electrical enclosures and control panels
Sheet metal structures and frames
Precision mechanical assemblies
Quality Control & Testing
Incoming material inspection for chemical composition and mechanical properties
Dimensional verification using go/no-go gauges
Hardness testing to confirm strength grade
Tensile strength testing for load-bearing verification
Coating thickness and surface finish inspection
Final random inspection before shipment to ensure consistency8.Installation Guidelines
Use a compatible hex key or torque-controlled driver
Ensure correct countersink diameter and depth before installation
Apply torque gradually to avoid thread or head damage
Verify flush seating after tightening
Avoid over-tightening to maintain mechanical performance
FAQ
Q: How do I select DIN 7991 hex socket screw size?
A: Choose diameter and length based on material thickness, load requirement, and ensure flush countersunk installation.
Q: Which materials are best for DIN 7991 countersunk screws in corrosive environments?
A: Stainless steel grades A2-70, A4-70, A4-80 or coated carbon steel (zinc plated / black oxide) for corrosion resistance.
Q: Can DIN 7991 hex socket countersunk screws be used in aluminum assemblies?
A: Yes, but torque control and correct countersink depth are required to prevent thread stripping and surface damage.
Q: What ensures stable torque performance in DIN 7991 socket head countersunk screws?
A: Proper ISO-matched hex key size and controlled torque application reduce rounding and improve fastening reliability.
Q: What should be checked when sourcing DIN 7991 fasteners?
A: Verify grade (8.8 / 10.9 / 12.9), tensile strength, coating quality, and compliance with DIN 7991 / ISO 10642 standards.
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