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FULLERKREG DIN 931 Grade 8.8 partially threaded hexagon bolts are manufactured from medium carbon steel (35K) to Property Class 8.8, with a hot dip galvanised (HDG) surface finish per ISO 10684. Hot dip galvanising deposits a thick zinc coating (typically 45–85 μm) by immersing the fastener in molten zinc at approximately 450°C — providing dramatically superior corrosion protection compared to electroplated zinc (5–8 μm), with a typical outdoor service life of 20–50+ years in moderate environments.
The partially threaded shank — with a smooth unthreaded grip length beneath the head — provides precise shear load transfer through the bolt body, making DIN 931 the preferred choice for structural connections, flanged joints, and outdoor infrastructure where the bolt passes through clearance holes and the thread engages only in the nut or tapped hole. DIN 931 is equivalent to ISO 4014.
| Standard | DIN 931 ≡ ISO 4014 (Partially Threaded Hexagon Head Bolts) |
| Galvanising Standard | ISO 10684 (Hot Dip Galvanised Fasteners) |
| Thread | Metric coarse per ISO 261 / DIN 13 |
| Thread Coverage | Partial thread — unthreaded grip length beneath head |
| Head Type | Hexagon head — driven by open-end wrench, ring spanner, or socket |
| Material | Carbon Steel 35K (medium carbon steel) |
| Property Class | 8.8 |
| Surface Finish | Hot Dip Galvanised (HDG) — molten zinc bath at ~450°C |
| Zinc Coating Thickness | 45 – 85 μm (per ISO 10684) — vs 5–8 μm for electroplated zinc |
| Salt Spray Resistance | ≥ 1,000 hours to red rust (typical) — vs ~240h for Zinc CR3 |
| Outdoor Service Life | 20–50+ years in moderate environments (C2–C3 per ISO 9223) |
| Thread Tolerance | Overcut (tapped oversize) after galvanising to restore thread fit — use HDG nuts |
| Size Range | M6 – M64 |
| Length Range | 25 mm – 300 mm (size-dependent) |
| Related Standard | DIN 933 Grade 8.8 HDG (fully threaded) | ISO 4014 | ISO 10684 | ISO 898-1 |
| [Product Photo 1] | [Product Photo 2] | [Product Photo 3] | [Product Photo 4] |
All dimensions in millimeters (mm). Data per DIN 931 / ISO 4014 standard. Note: HDG coating (45–85μm) adds measurable thickness — use HDG nuts (overcut) for correct thread fit.
| Thread (d) | Pitch (mm) | s — A/F (mm) | e — A/C (mm) | k — Head Height (mm) | ds — Shank Ø (mm) |
|---|---|---|---|---|---|
| M6 | 1.0 | 10 | 11.05 | 4.0 | 5.7 |
| M8 | 1.25 | 13 | 14.38 | 5.3 | 7.64 |
| M10 | 1.5 | 17 | 18.90 | 6.4 | 9.64 |
| M12 | 1.75 | 19 | 21.10 | 7.5 | 11.57 |
| M14 | 2.0 | 22 | 24.49 | 8.8 | 13.57 |
| M16 | 2.0 | 24 | 26.75 | 10.0 | 15.57 |
| M20 | 2.5 | 30 | 33.53 | 12.5 | 19.48 |
| M24 | 3.0 | 36 | 39.98 | 15.0 | 23.48 |
| M27 | 3.0 | 41 | 45.20 | 17.0 | 26.48 |
| M30 | 3.5 | 46 | 50.85 | 18.7 | 29.48 |
| M36 | 4.0 | 55 | 60.79 | 22.5 | 35.38 |
| M42 | 4.5 | 65 | 71.30 | 26.0 | 41.38 |
| M48 | 5.0 | 75 | 82.60 | 30.0 | 47.38 |
| M56 | 5.5 | 85 | 93.56 | 35.0 | 55.26 |
| M64 | 6.0 | 95 | 104.86 | 40.0 | 63.26 |
* s = across flats (A/F); e = across corners (A/C); k = head height; ds = unthreaded shank diameter (max). All dimensions per DIN 931 / ISO 4014 before galvanising. HDG coating adds 45–85μm per surface — threads are overcut after galvanising to restore fit.
| Thread (d) | b — L ≤ 125 mm | b — 125 < L ≤ 200 mm | b — L > 200 mm |
|---|---|---|---|
| M6 | 18 | 24 | — |
| M8 | 22 | 28 | — |
| M10 | 26 | 32 | 45 |
| M12 | 30 | 36 | 49 |
| M14 | 34 | 40 | 53 |
| M16 | 38 | 44 | 57 |
| M20 | 46 | 52 | 65 |
| M24 | 54 | 60 | 73 |
| M27 | 60 | 66 | 79 |
| M30 | 66 | 72 | 85 |
| M36 | 78 | 84 | 97 |
| M42 | — | 96 | 109 |
| M48 | — | 108 | 121 |
| M56 | — | — | 137 |
| M64 | — | — | 153 |
* b = threaded length. Grip length = L − b − k (approximate). Per DIN 931 / ISO 4014.
| Property | Value |
|---|---|
| Base Material | Carbon Steel 35K (medium carbon steel) |
| Property Class | 8.8 |
| Tensile Strength (Rm) | ≥ 800 MPa (d ≤ M16) / ≥ 830 MPa (d > M16) |
| Lower Yield Strength (ReL) | ≥ 640 MPa (d ≤ M16) / ≥ 660 MPa (d > M16) |
| Proof Load Stress (Sp) | ≥ 580 MPa |
| Hardness | 245 – 335 HV |
| Galvanising Process | Hot dip galvanising — immersion in molten zinc at ~450°C |
| Galvanising Standard | ISO 10684 (Fasteners — Hot Dip Galvanised Coatings) |
| Zinc Coating Thickness | 45 – 85 μm (min. 40μm per ISO 10684) |
| Zinc Coating Type | Metallurgically bonded zinc-iron alloy layers + pure zinc outer layer |
| Salt Spray Resistance | ≥ 1,000 hours to red rust (typical) |
| Outdoor Service Life | 20–50+ years (C2–C3 environment per ISO 9223); 10–25 years in C4 industrial |
| Thread Treatment | Threads overcut (tapped oversize) after galvanising to restore metric thread fit |
| Nut Requirement | Must use HDG overcut nuts — standard nuts will NOT fit HDG bolts |
| Appearance | Matte grey / spangled zinc surface |
| Temperature Limit | Up to +200°C (zinc coating degrades above this) |
| Magnetic | Yes |
| Property | Hot Dip Galvanised (This Product) | Zinc CR3 Electroplated |
|---|---|---|
| Process | Immersion in molten zinc at ~450°C | Electrodeposition from zinc salt solution |
| Coating thickness | 45–85 μm | 5–8 μm |
| Coating type | Metallurgically bonded Zn-Fe alloy + pure Zn | Pure zinc layer |
| Adhesion | Metallurgical bond — cannot be peeled | Mechanical/electrochemical bond |
| Salt spray resistance | ≥ 1,000 hours to red rust | ≥ 240 hours to red rust |
| Outdoor service life | 20–50+ years (C2–C3) | 3–10 years (C2–C3) |
| Thread fit | Threads overcut after galvanising — requires HDG nuts | 5–8μm — does not affect standard thread fit |
| Appearance | Matte grey / spangled | Bright silver / light blue iridescent |
| Temperature limit | +200°C | +120°C |
| RoHS compliance | Yes (zinc is RoHS compliant) | Yes (Cr3+ trivalent) |
| Best for | Outdoor structural, civil engineering, long-term exposure | General industrial, automotive, indoor/mild outdoor |
| Cost | Higher (process cost) | Lower |
Approximate weights per 100 pieces. Based on carbon steel density (7.85 g/cm³) plus HDG coating weight (~0.6 kg/m² for 85μm coating). Actual weight slightly higher than bare steel.
| L (mm) | M6 | M8 | M10 | M12 | M16 | M20 | M24 | M30 | M36 |
|---|---|---|---|---|---|---|---|---|---|
| 30 | 0.17 | 0.35 | 0.62 | — | — | — | — | — | — |
| 40 | 0.22 | 0.47 | 0.84 | 1.27 | 2.50 | — | — | — | — |
| 50 | 0.27 | 0.59 | 1.06 | 1.61 | 3.17 | 5.58 | — | — | — |
| 60 | 0.32 | 0.71 | 1.28 | 1.95 | 3.85 | 6.78 | 11.2 | — | — |
| 70 | 0.37 | 0.83 | 1.49 | 2.28 | 4.53 | 7.97 | 13.2 | — | — |
| 80 | 0.43 | 0.95 | 1.71 | 2.62 | 5.21 | 9.17 | 15.1 | 27.9 | — |
| 100 | 0.53 | 1.19 | 2.15 | 3.29 | 6.57 | 11.6 | 19.1 | 35.4 | 59.6 |
| 120 | 0.64 | 1.43 | 2.59 | 3.96 | 7.93 | 13.9 | 23.1 | 42.9 | 72.4 |
| 140 | 0.74 | 1.67 | 3.02 | 4.63 | 9.29 | 16.3 | 27.1 | 50.4 | 85.2 |
| 160 | — | 1.91 | 3.46 | 5.30 | 10.65 | 18.7 | 31.1 | 57.9 | 98.0 |
| 200 | — | 2.39 | 4.33 | 6.64 | 13.37 | 23.4 | 39.0 | 72.9 | 124 |
| 240 | — | — | 5.20 | 7.98 | 16.09 | 28.2 | 47.0 | 87.9 | 149 |
| 300 | — | — | — | 10.00 | 20.17 | 35.4 | 59.0 | 110 | 188 |
* Weights include HDG coating. Actual weights may vary by coating thickness. Contact FULLERKREG for precise weight certificates and inspection reports.
Q: Why can’t I use standard nuts with HDG bolts?
A: Hot dip galvanising deposits a thick zinc coating (45–85μm) on all surfaces including threads. This coating is too thick for standard metric nuts to engage correctly. After galvanising, the bolt threads are overcut (tapped oversize) to restore the thread profile — but this means the thread is now slightly larger than standard. HDG overcut nuts (also galvanised with overcut threads) must be used. Using standard nuts on HDG bolts will result in cross-threading, seizure, or incorrect torque readings.
Q: How does hot dip galvanising compare to electroplated zinc for outdoor use?
A: HDG provides dramatically better outdoor corrosion protection: 45–85μm zinc coating vs 5–8μm for electroplated zinc, giving 5–10× longer service life. HDG is the standard choice for structural steel in outdoor, coastal, and industrial environments. Electroplated zinc is suitable for general indoor/mild outdoor use where long-term exposure is not a concern.
Q: Does hot dip galvanising affect the mechanical properties of Grade 8.8 bolts?
A: The galvanising process (450°C) can slightly affect the mechanical properties of high-strength fasteners. For Grade 8.8, the process temperature is below the tempering temperature of the steel, so mechanical properties are generally maintained. ISO 10684 specifies that HDG fasteners must be tested after galvanising to confirm compliance with the property class requirements.
Q: What lubricant should I use with HDG bolts?
A: Use a zinc-compatible lubricant — wax-based lubricants, molybdenum disulfide (MoS₂) paste, or zinc-compatible anti-seize compounds are all suitable. Avoid copper-based anti-seize in contact with zinc coatings in wet environments (galvanic incompatibility). Always lubricate HDG threads before installation to achieve accurate torque control.
Q: What is the difference between DIN 931 and DIN 933 in HDG Grade 8.8?
A: DIN 931 HDG Grade 8.8 is partially threaded — smooth shank beneath the head for shear load transfer. DIN 933 HDG Grade 8.8 is fully threaded. Choose DIN 931 for structural shear-critical connections; choose DIN 933 when maximum thread engagement or grip-length flexibility is needed.
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