M12 Countersunk Bolts Allen Key Socket Screws DIN7991 High Tensile Grade 12.9

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M12 Countersunk Bolts Allen Key Socket Screws DIN7991 High Tensile Grade 12.9

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Thread dia. x Length: M12 x 20mm

Pack Quantity(Pcs): 2

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$8.47 USD

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In stock (500 units), ready to be shipped

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M12 Countersunk Allen Socket Screws DIN7991 — Flush-Fit Strength for Demanding Assemblies

When a protruding bolt head is not an option — whether you're building precision machinery, assembling steel frames, or mounting components where clearance is tight — standard hex bolts simply don't cut it. Engineers, fabricators, and serious DIYers who need a flush, low-profile fastening solution rely on M12 countersunk Allen key socket screws to get the job done cleanly and securely.

Each screw in this listing is an M12 diameter countersunk (flat-head) socket screw manufactured to DIN 7991 and rated Grade 12.9 high tensile alloy steel. Available lengths run from 20mm (≈13/16") to 100mm (≈3-15/16"). Shorter lengths (20mm–60mm) are fully threaded; longer lengths (70mm–100mm) are partially threaded for improved shear resistance. Pack quantities range from 1 to 50 pieces so you can order exactly what your project requires.

Typical applications include CNC machine bed assembly, automotive suspension brackets, steel-to-steel structural connections, and industrial fixture building — anywhere you need a high tensile countersunk bolt that disappears flush into the surface while holding under extreme load.

🔵 Compatibility: ISO metric coarse thread M12 × 1.75mm pitch — fits any M12 nut, threaded insert, or tapped hole per DIN 7991 / ISO 68-1. Requires a 10mm hex (Allen) key for installation.

⚠️ Note: Grade 12.9 alloy steel is not stainless. For outdoor or corrosive environments, apply a protective coating or contact us to confirm suitability before ordering.

✅ Key Features of These M12 Countersunk Allen Socket Screws DIN7991

💪Grade 12.9 High Tensile Strength — Minimum tensile strength of 1220 MPa makes these screws suitable for high-load structural and mechanical assemblies where standard-grade fasteners would fail.
🔩DIN 7991 Flat Countersunk Head — The 90° countersunk head sits perfectly flush with the mating surface, eliminating snag points and allowing smooth movement of adjacent parts in machinery and fixtures.
🔑Internal Hex (Allen Key) Drive — The recessed socket drive allows torque application in confined spaces where a standard wrench cannot reach, ideal for tight machine frames and enclosed assemblies.
📏Wide Length Range — Full & Partial Thread — Choose from 20mm to 60mm fully threaded for thinner panels, or 70mm to 100mm partially threaded for thicker structural joints requiring shear-resistant shoulder engagement.
📦Flexible Pack Quantities — Available in 1, 2, 4, 5, 8, 10, 15, 20, or 50-piece packs so you can match your exact project quantity — from a single prototype fix to a full production run.
⚙️ISO Metric Coarse Thread M12 × 1.75 — Standard pitch ensures compatibility with off-the-shelf M12 nuts, threaded inserts, and tapped holes across automotive, industrial, and fabrication applications.

📐 Technical Specifications — M12 Countersunk Socket Screws

Standard	DIN 7991
Thread Diameter	M12
Thread Pitch	1.75mm (ISO Metric Coarse)
Available Lengths	20mm (≈13/16") — 100mm (≈3-15/16")
Thread Type	Fully threaded: 20–60mm \| Partially threaded: 70–100mm
Head Type	Flat countersunk (90° included angle)
Drive Type	Internal hex socket (Allen key)
Hex Key Size	10mm
Material	Alloy steel
Grade / Strength Class	12.9 (Tensile strength ≥ 1220 MPa)
Surface Finish	See variant options
Pack Quantity	1 / 2 / 4 / 5 / 8 / 10 / 15 / 20 / 50 pcs (select above)
Head Diameter (approx.)	Contact us to confirm exact DIN 7991 M12 head dimensions

❓ Frequently Asked Questions

How do I choose the right length for M12 countersunk socket screws?

Measure the total thickness of the materials being joined, then subtract the countersink depth so the head sits flush. For example, M12 x 25mm (≈1") is typically used for joining two 10–12mm panels. Lengths from 20mm (≈13/16") to 100mm (≈3-15/16") are available in this listing — select the size that gives you at least 1.5× the thread diameter of engagement in the tapped material.

What does Grade 12.9 mean and how strong are these screws?

Grade 12.9 is among the highest strength classifications for metric fasteners. It indicates a minimum tensile strength of 1220 MPa and a proof load of approximately 1100 MPa. These screws are generally used in high-stress mechanical assemblies, heavy machinery, and structural applications where standard Grade 8.8 or 10.9 bolts are insufficient.

Are these countersunk screws suitable for outdoor or corrosive environments?

Grade 12.9 alloy steel screws are not inherently corrosion-resistant. For outdoor or humid environments, we recommend applying a corrosion-inhibiting coating or using stainless steel alternatives. If you need to use these outdoors, pairing them with anti-seize compound or zinc-based primer is generally advisable. Contact us if you need guidance on coating options.

What thread standard do these M12 screws use — are they compatible with standard nuts?

These screws conform to DIN 7991 and use standard ISO metric coarse thread (M12 × 1.75mm pitch). They are compatible with any M12 metric nut, threaded insert, or tapped hole following ISO 68-1 thread standards — including those used in automotive, industrial machinery, and structural steel fabrication.

What Allen key (hex key) size do I need to drive these screws?

M12 DIN 7991 countersunk socket screws typically require a 10mm hex (Allen) key. Always verify with a test fit before applying full torque to avoid rounding the socket. A torque wrench with a hex bit is recommended for critical structural joints.

What is the difference between fully threaded and partially threaded variants?

Fully threaded screws (20mm–60mm in this listing) have threads running the entire shank length, providing maximum grip in thinner materials. Partially threaded screws (70mm–100mm) have an unthreaded shank section that acts as a shoulder, improving shear resistance and alignment accuracy in thicker assemblies — commonly used in precision fixtures and heavy structural joints.

How do I choose between buying a 2-pack vs. a 50-pack?

For one-off repairs or prototyping, the 1- or 2-piece packs let you test fit without over-buying. For production runs, maintenance kits, or workshop stock, the 10-, 20-, or 50-piece packs offer a lower per-unit cost. Select your pack size from the Pack Quantity variant option above.

🛒 Select your thread length and pack quantity above, then add to cart — ships from our US warehouse.