Longze Precision Flat Head Countersunk Screws | DIN 7991 / ISO 10642 | Metric & Inch
Product Title
Longze Precision Flat Head Countersunk Screws | DIN 7991 / ISO 10642 | Metric & Inch
Product Summary
Longze Precision Countersunk Screws are designed for flush-surface fastening in high-precision machinery and structural assemblies. Manufactured in Yongnian, China, our fasteners ensure a
perfect 90-degree fit, eliminating protruding bolt heads for a seamless finish.
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✔ Standard Compliance: DIN 7991, ISO 10642, ASME B18.3.
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✔ High-Tensile Performance: Grade 10.9 and 12.9 high-strength options available.
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✔ Precision Drive: Deep-cut hex sockets to prevent stripping during high-torque installation.
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Standards: DIN 7991, ISO 10642, ASME B18.3 (Metric & Inch).
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Diameter Range: M3 to M24 | #4 – 1".
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Material Grade: Property Class 8.8, 10.9, 12.9 | Stainless Steel A2/A4.
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Surface Finish: Black Oxide, Zinc Plated, Plain Steel, Dacromet.
- Ensuring Grade 10.9 and 12.9 structural integrity through rigorous heat treatment.
| Property Class | Tensile Strength | Yield Strength | Rockwell Hardness (HRC) | Core Hardness (HV) |
| Grade 8.8 | 800 MPa | 640 MPa | 22 – 32 HRC | 250 – 320 HV |
| Grade 10.9 | 1040 MPa | 940 MPa | 32 – 39 HRC | 320 – 380 HV |
| Grade 12.9 | 1220 MPa | 1100 MPa | 39 – 44 HRC | 385 – 435 HV |
| SS316 (A4-70) | 700 MPa | 450 MPa | 20 – 28 HRC | 200 – 280 HV |
- Precise head diameter and socket depth for flush-mount perfection.
| Thread Size | Head Diameter (max) | Head Height (max) | Socket Size (s) | Key Engagement (min) |
| M6 | 12.0 mm | 3.3 mm | 4.0 mm | 2.5 mm |
| M8 | 16.0 mm | 4.4 mm | 5.0 mm | 3.5 mm |
| M10 | 20.0 mm | 5.5 mm | 6.0 mm | 4.4 mm |
| M12 | 24.0 mm | 6.5 mm | 8.0 mm | 4.6 mm |
| M16 | 30.0 mm | 7.5 mm | 10.0 mm | 5.3 mm |
- Matching the right coating and material to your industrial environment.
| Surface Treatment | Korozyon Direnci | Salt Spray Test | Best Applications |
| Black Oxide (Oiled) | Basic | 24 - 48 Hours | Internal Machinery, Oil & Gas |
| Zinc Plated (Blue/White) | Moderate | 72 - 96 Hours | Electronics, Light Engineering |
| Stainless Steel 316 | Excellent | 500+ Hours | Marine, Food, Chemical Plants |
| Dacromet / Geomet | High | 500 - 1000 Hours | Automotive & Outdoor Structural |
Avoid Pitfalls:
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90° Angle Accuracy: We prevent uneven seating by strictly controlling the countersunk angle during the forging process, ensuring 100% flush fit with your workpieces.
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Hex Socket Integrity: Many suppliers provide shallow sockets that strip under torque. Our deep-cut hex drive ensures maximum tool engagement and longer service life.
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Surface Decarburization Control: We use advanced atmospheric heat treatment to prevent soft spots, ensuring Grade 10.9/12.9 screws maintain full tensile strength.
Perfect Fit Assembly:
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Flush Mounting: Designed specifically for applications where the bolt head must remain level with or below the surface of the assembly.
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Tool Compatibility: Precision-engineered socket sizes compatible with all standard metric and imperial hex keys and power bits.
Quality Control & Logistics:
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ISO 9001 Certified: 5-step QC including thread gauging, hardness testing, and salt spray analysis.
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Sea-Worthy Packaging: Reinforced cartons + Fumigation-Free Pallets with moisture-proof lining for safe international maritime transit.
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Q: Can you provide MTC (Mill Test Certificates)? A: Yes, full traceability and MTC are provided for every batch of 10.9/12.9 screws.
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Q: What is the lead time for DIN 7991 Black Oxide screws? A: Standard metric sizes are typically ready for shipment from our Yongnian factory within 7–12 days.
- Planning a heavy-duty steel structure? Don't risk your project on low-grade fasteners. Send your requirements → Get an expert bolt recommendation + quote within 12 hours.
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