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FULLERKREG DIN 6912 A4 low head socket cap screws are precision-engineered metric fasteners combining a reduced-height hex socket head with a pilot recess (centre hole) in the socket. The pilot recess enables use of a ball-end hex key at angles up to 25°, making these screws ideal for confined spaces and recessed installations where straight-on access is impossible.
Manufactured from A4 stainless steel (SUS316 / 1.4401) — the marine-grade stainless steel — FULLERKREG DIN 6912 A4 screws deliver superior resistance to chloride-induced pitting and crevice corrosion compared to A2 (SUS304), making them the preferred choice for coastal, marine, offshore, chemical processing, and other aggressive environments.
| Feature | DIN 6912 (This Product) | DIN 7984 | DIN 912 (Standard Socket Cap) |
|---|---|---|---|
| Head Height | Low (approx. 60% of DIN 912) | Low (approx. 60% of DIN 912) | Standard full height |
| Pilot Recess (Centre Hole) | ✅ Yes — centre hole in socket | ❌ No | ❌ No |
| Ball-End Hex Key Access | ✅ Up to 25° off-axis | ⚠️ Limited — ball-end slips without pilot | ⚠️ Limited — ball-end slips without pilot |
| Hex Key Size (e.g. M6) | 4 mm | 3 mm (smaller than DIN 6912) | 5 mm (full size) |
| Head Diameter dk (e.g. M6) | 10.0 mm | 10.0 mm | 10.0 mm |
| Head Height k (e.g. M6) | 3.3 mm | 3.0 mm | 6.0 mm |
| Socket Depth (e.g. M6) | Deeper — accommodates pilot recess | Shallower — no pilot recess | Full depth standard socket |
| Torque Capacity | Medium — larger hex key than DIN 7984 | Lower — smaller hex key size | Full torque capacity |
| Clearance Required | Minimal — ideal for thin flanges | Minimal — ideal for thin flanges | Standard clearance needed |
| Governing Standard | DIN 6912 / ISO 14580 | DIN 7984 | DIN 912 / ISO 4762 |
| Best For | Low clearance + angled access required | Low clearance, straight-on access only | General-purpose, high-torque applications |
The critical difference between A4 (SUS316) and A2 (SUS304) is the addition of 2–3% molybdenum (Mo) in A4, which dramatically improves resistance to chloride-induced pitting and crevice corrosion — the primary failure mode of stainless steel in marine and chemical environments.
| Property | A4 / SUS316 (This Product) | A2 / SUS304 |
|---|---|---|
| Molybdenum Content | 2.0 – 3.0% | None |
| Chloride / Salt Resistance | ✅ Excellent — marine grade | ⚠️ Moderate — susceptible to pitting |
| Coastal / Marine Use | ✅ Recommended | ❌ Not recommended |
| Chemical Processing | ✅ Suitable for many acids & chlorides | ⚠️ Limited |
| Swimming Pool Environments | ✅ Suitable | ❌ Risk of pitting |
| Food & Pharmaceutical | ✅ Preferred grade | ✅ Acceptable |
| Tensile Strength (A-70 class) | 700 MPa (min.) | 700 MPa (min.) |
| Cost | Higher (Mo alloy premium) | Lower |
Manufactured from A4 stainless steel (SUS316 / EN 1.4401) — molybdenum-alloyed austenitic stainless steel with superior corrosion resistance, particularly in chloride-rich environments.
| Property | Value | Standard Reference |
|---|---|---|
| Material Grade | A4 (SUS316 / 1.4401) | ISO 3506 / EN 10088 |
| Property Class | A4-70 | ISO 3506-1 |
| Tensile Strength (min.) | 700 MPa | ISO 3506-1 |
| 0.2% Proof Stress (min.) | 450 MPa | ISO 3506-1 |
| Elongation (min.) | 20% | ISO 3506-1 |
| Hardness (max.) | 220 HV | ISO 3506-1 |
| Chromium Content | 16.0 – 18.0% | EN 10088 |
| Nickel Content | 10.0 – 14.0% | EN 10088 |
| Molybdenum Content | 2.0 – 3.0% | EN 10088 |
| Magnetic | Non-magnetic (annealed state) | — |
| Corrosion Resistance | Excellent — marine grade, chloride-resistant | — |
| Operating Temperature | −50°C to +300°C (continuous) | — |
All dimensions per DIN 6912:2021. Thread per ISO 68-1 metric coarse.
| Size | Thread Pitch (mm) | Head Dia. dk (mm) | Head Height k (mm) | Hex Key Size s (mm) | Pilot Recess Dia. (mm) | Common Lengths (mm) |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 5.5 | 1.65 | 2.0 | 1.0 | 5, 6, 8, 10, 12, 16, 20 |
| M4 | 0.7 | 7.0 | 2.2 | 2.5 | 1.5 | 6, 8, 10, 12, 16, 20, 25 |
| M5 | 0.8 | 8.5 | 2.75 | 3.0 | 2.0 | 8, 10, 12, 16, 20, 25, 30 |
| M6 | 1.0 | 10.0 | 3.3 | 4.0 | 2.0 | 10, 12, 16, 20, 25, 30, 35, 40 |
| M8 | 1.25 | 13.0 | 4.4 | 5.0 | 2.5 | 12, 16, 20, 25, 30, 35, 40, 50 |
| M10 | 1.5 | 16.0 | 5.5 | 6.0 | 3.0 | 16, 20, 25, 30, 35, 40, 50, 60 |
| M12 | 1.75 | 18.0 | 6.6 | 8.0 | 4.0 | 20, 25, 30, 35, 40, 50, 60, 70 |
| M14 | 2.0 | 21.0 | 7.7 | 10.0 | 4.0 | 25, 30, 35, 40, 50, 60, 70, 80 |
| M16 | 2.0 | 24.0 | 8.8 | 10.0 | 4.0 | 25, 30, 35, 40, 50, 60, 70, 80, 100 |
| M20 | 2.5 | 30.0 | 11.0 | 12.0 | 5.0 | 30, 35, 40, 50, 60, 70, 80, 100 |
All dimensions are nominal per DIN 6912:2021. Consult FULLERKREG product listings for exact available size/length combinations. Tolerances per ISO 4759-1.
The pilot recess (also called centre hole or pilot hole) is a small cylindrical bore at the centre of the hex socket. It serves two critical functions:
This feature makes DIN 6912 the preferred choice over DIN 7984 for recessed bolt patterns, flanged joints, and any assembly where the fastener is not directly accessible from above.
A4 (SUS316) stainless steel contains 2–3% molybdenum, which significantly enhances resistance to chloride pitting and crevice corrosion compared to standard austenitic grades. The passive chromium oxide layer self-repairs when exposed to oxygen:
Recommended installation torque values for A4-70 DIN 6912 screws (dry, unlubricated, μ = 0.12):
| Size | Recommended Torque (N·m) | Hex Key Size (mm) | Notes |
|---|---|---|---|
| M3 | 0.5 – 0.7 | 2.0 | Use T-handle or short-arm key; avoid over-torque |
| M4 | 1.2 – 1.5 | 2.5 | — |
| M5 | 2.5 – 3.0 | 3.0 | — |
| M6 | 4.5 – 5.5 | 4.0 | — |
| M8 | 11 – 13 | 5.0 | — |
| M10 | 22 – 26 | 6.0 | — |
| M12 | 38 – 45 | 8.0 | — |
| M14 | 60 – 72 | 10.0 | — |
| M16 | 95 – 110 | 10.0 | — |
| M20 | 185 – 215 | 12.0 | — |
Torque values are indicative for dry conditions with standard thread fit. Lubrication reduces required torque by approximately 20–25%. For critical joints, use a calibrated torque wrench and refer to joint-specific engineering calculations. A4 stainless is susceptible to galling — apply anti-seize compound (e.g., molybdenum disulphide or PTFE-based) for M10 and above, or where repeated assembly/disassembly is required.
Stainless steel fasteners — including A4 — are prone to galling (cold welding / thread seizure) during installation, particularly at larger diameters and higher torques. To prevent galling:
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