DIN 912 / ISO 4762 Socket Head Cap Screws (Allen Bolts) | Specifications

Standard Overview

What Are DIN 912 & ISO 4762?

The international metric standard for cylindrical head socket screws driven internally with a hexagonal Allen key.

DIN 912 (and its international equivalent ISO 4762) specifies the metric dimensions, tolerances, and mechanical standards for socket head cap screws. These fasteners feature a cylindrical head with a recessed hexagonal socket drive that allows for high torque application using an Allen wrench or hex bit. The standard covers two primary manufacturing variations:

Standard Metric Coarse

DIN 912 / ISO 4762

Standard coarse pitch metric threads for general mechanical engineering, machinery components, and structural clamping. Sizes from M1.6 to M64.

Drive: Hexagonal Allen Socket | Thread: Metric Coarse (ISO 261)

Metric Fine Pitch

DIN 912 Fine Thread

Fine pitch threads for specialized applications requiring higher tension retention, micro-adjustments, or thin-walled component tapped holes.

Drive: Hexagonal Allen Socket | Thread: Metric Fine (ISO 261)

                        Technical Advantage: DIN 912 socket head screws are engineered for compact assembly spaces where external wrench access (like standard DIN 931/933 hex bolts) is impossible. The cylindrical head can be fully counterbored flush into mechanical components, improving safety, aerodynamic clearance, and aesthetic finish.
                    

Technical Specifications

Property Classes, Materials & Finishes

Material Grades & Classes

Grade 12.9 Alloy Steel: The ultimate high-strength standard for DIN 912 fasteners. Quenched and tempered alloy steel delivering an extreme tensile strength of 1200 MPa. Designed for high-stress machinery, dies, and automotive engines.
Grade 10.9 & 8.8 Carbon Steel: Medium to high tensile strength options offering high ductile resistance for structural fabrication, machinery housing, and heavy equipment mounting.
Stainless Steel A2-70 (AISI 304): Corrosion-resistant stainless steel suitable for food processing, architectural fabrication, and general outdoor mechanical assemblies.
Stainless Steel A4-80 / A4-70 (AISI 316): Marine-grade stainless steel fortified with molybdenum for maximum resistance against aggressive chloride environments, chemical processing, and offshore platforms.

Mechanical Properties (ISO 898-1 / ISO 3506-1)

Property	Grade 8.8	Grade 10.9	Grade 12.9	Stainless A2-70 / A4-70
Tensile Strength (Rm)	800 MPa	1040 MPa	1200 MPa	700 MPa
Yield Strength (Rp0.2)	640 MPa	940 MPa	1100 MPa	450 MPa
Elongation (A)	≥ 12%	≥ 9%	≥ 8%	≥ 0.4d
Hardness (HRC / HV)	22 – 32 HRC	32 – 39 HRC	39 – 44 HRC	160 – 250 HV
Surface Finish	Black Oxide / Zinc	Black Oxide / Zinc	Black Oxide / Geomet	Plain (Passivated)

Grade 12.9 bolts must be carefully coated to avoid hydrogen embrittlement. Electro-galvanizing Grade 12.9 requires strict de-embrittlement baking per ISO 4042, which is why black oxide, Geomet, or zinc-nickel finishes are preferred for 12.9 fasteners.

Chemical Composition Standards

Grade	Carbon (C)	Manganese (Mn)	Phosphorus (P)	Sulfur (S)	Chromium (Cr) / Nickel (Ni)
Class 8.8	0.25 – 0.55%	≥ 0.35%	≤ 0.025%	≤ 0.025%	Optional additives
Class 10.9	0.20 – 0.55%	≥ 0.30%	≤ 0.025%	≤ 0.025%	Cr, Mo, or B added
Class 12.9	0.28 – 0.50%	≥ 0.45%	≤ 0.025%	≤ 0.025%	Cr, Mo, or V alloyed
Stainless A2 (304)	≤ 0.08%	≤ 2.00%	≤ 0.045%	≤ 0.030%	17.5–19.5% Cr \| 8.0–10.5% Ni
Stainless A4 (316)	≤ 0.08%	≤ 2.00%	≤ 0.045%	≤ 0.030%	16.5–18.5% Cr \| 10.0–13.0% Ni \| 2.0–2.5% Mo

The inclusion of molybdenum (2.0-2.5%) in A4 stainless steel prevents pitting and crevice corrosion under severe marine atmosphere and high-salinity coastal conditions in the GCC.

Dimension Tables

DIN 912 / ISO 4762 Dimensions

Standard metric dimensions in millimetres (mm). All parameters adhere to ISO 4762 standard tolerances.

Metric Socket Head Cap Screw Dimensions

Nominal Size (d)	Thread Pitch (P)	Head Diam. dk (max)	Head Height k (max)	Allen Key Size s	Counterbore Diam. (min)
M3	0.50 mm	5.50 mm	3.00 mm	2.5 mm	6.0 mm
M4	0.70 mm	7.00 mm	4.00 mm	3.0 mm	8.0 mm
M5	0.80 mm	8.50 mm	5.00 mm	4.0 mm	10.0 mm
M6	1.00 mm	10.00 mm	6.00 mm	5.0 mm	11.0 mm
M8	1.25 mm	13.00 mm	8.00 mm	6.0 mm	15.0 mm
M10	1.50 mm	16.00 mm	10.00 mm	8.0 mm	18.0 mm
M12	1.75 mm	18.00 mm	12.00 mm	10.0 mm	20.0 mm
M16	2.00 mm	24.00 mm	16.00 mm	14.0 mm	26.0 mm
M20	2.50 mm	30.00 mm	20.00 mm	17.0 mm	33.0 mm
M24	3.00 mm	36.00 mm	24.00 mm	19.0 mm	40.0 mm

                    Counterbore Engineering Note: To recess a DIN 912 bolt head completely flush with the surface of a workpiece, machine the counterbore diameter equal to or greater than the minimum counterbore diameter shown above, with depth equal to the maximum head height ($k$).
                

Application Guidance

Where & How to Use DIN 912 Bolts

Precision Machinery & Tooling

Essential in tooling jigs, molding dies, CNC machinery, and high-precision automation units where smooth surfaces and compact component spacing are required.

Oil, Gas & Petrochemicals

Grade 12.9 black alloy and Stainless A4-80 Allen bolts are heavily used in high-pressure valve bodies, pumps, turbines, and processing skids across UAE refineries.

Automotive & Aerospace

Drivetrain, engine block mountings, and high-stress transmission housings benefit from the exceptional clamp load and shear resistance of Grade 12.9 DIN 912 screws.

Marine & Offshore Equipment

A4-80 stainless steel socket head cap screws resist severe saltwater oxidation, rendering them indispensable for boat building, desalination plant hardware, and docks.

High-Clamping Safety Joints

Internal hex socket drive minimizes drive slip (cam-out) during assembly, enabling precise preloading using calibrated torque wrenches.

Complete RFQ Format

"DIN 912 Socket Head Cap Screw, M12 x 50mm, Grade 12.9, Self-Color (Black Oxide), with EN 10204 3.1 Mill Test Report."

Related Standards

Complementary Fastener Standards

Standard	Description	Relationship to DIN 912
ISO 4762	Socket head cap screws — metric series	Direct international equivalent standard to DIN 912
DIN 7984	Low head socket head cap screws	Low profile alternative head height for thin clearances
DIN 7991 / ISO 10642	Countersunk socket head cap screws	Flat-top 90° countersunk flush mounting variant
ISO 7380	Button head socket cap screws	Rounded dome-head design for decorative or thin sheet joints
DIN 934 / ISO 4032	Metric hexagon nuts	Matching hex nuts for through-hole bolting assemblies
DIN 125 / ISO 7089	Plain flat washers	Companion washers placed under socket screws or nuts
DIN 127	Spring lock washers	Anti-loosening split lock washers for socket screws
ISO 898-1	Mechanical properties of carbon steel bolts	Defines Grade 8.8, 10.9, and 12.9 performance
ISO 3506-1	Mechanical properties of stainless steel bolts	Defines A2-70, A4-70, and A4-80 performance

FAQ

Frequently Asked Questions

Is DIN 912 identical to ISO 4762?

Yes, virtually identical. ISO 4762 is the international standardized equivalent of the retired DIN 912 standard. Dimensions, thread pitches, socket drive dimensions, and mechanical property requirements are completely interchangeable for commercial and industrial applications.

Why choose Grade 12.9 Allen bolts over Grade 8.8 hex bolts?

Grade 12.9 socket head cap screws deliver 50% higher tensile strength (1200 MPa vs 800 MPa) than Grade 8.8 hex bolts. This allows engineers to use smaller or fewer bolts while achieving identical or superior clamping force, significantly reducing component weight and footprint.

What coating is recommended for Grade 12.9 bolts in coastal UAE?

For Grade 12.9 bolts in humid or corrosive outdoor GCC environments, specify Geomet, Zinc Flake, or Black Oxide with rust-inhibiting oil. Electro-galvanizing should be approached cautiously due to hydrogen embrittlement risks. Alternatively, specify Stainless Steel A4-80 DIN 912 for severe marine exposure.

What is the difference between DIN 912, DIN 7984, and DIN 7991?

DIN 912 features a standard height cylindrical head. DIN 7984 features a low-profile cylindrical head for tight height clearances. DIN 7991 is a 90-degree countersunk flat-head socket screw designed to sit completely flush within a chamfered hole.

Are partial thread and full thread options available in DIN 912?

Yes. Shorter lengths of DIN 912 are threaded fully to the head, while longer nominal lengths feature a partial thread with an unthreaded shank, per standard DIN 912 manufacturing specifications.

Need DIN 912 Socket Head Screws in UAE & GCC?

We supply DIN 912 / ISO 4762 Allen bolts in Grade 8.8, 10.9, 12.9, Stainless Steel A2-70 & A4-80. Stocked from M2 to M64 in plain, black oxide, zinc plated, and hot-dip galvanized finishes. Fast dispatch from RAK FREEZONE across UAE & GCC.

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