DIN931 Partially Threaded Hex Bolt
DIN931 Partially Threaded Hex Bolt | ISO 4014 Marine Structural Bolt
Size: M6 – M64 | Grade: 8.8 / 10.9 / 12.9 / A4-80 | Material: Carbon Steel / Alloy Steel / SS316
TheDIN 931 hex bolt (equivalent to ISO 4014) is a partially threaded hex head bolt with a smooth unthreaded shank between the head and the thread section. Unlike fully threaded DIN 933 / ISO 4017 bolts, the unthreaded shank of DIN 931 can be positioned to cross the shear plane in structural joints — increasing effective shear strength by approximately 20–25% compared to a fully threaded bolt of the same diameter.
In marine and offshore environments, DIN 931 structural bolts are specified for engine room equipment mounting, pump and compressor baseplate anchoring, generator set foundations, crane pedestal connections, and hull-to-deck structural joints where lateral and dynamic loads dominate. Our DIN 931 hex bolts are manufactured per ISO 4014 dimensional requirements, available in sizes M6 through M64 with metric coarse thread per ISO 261.
Product Specification
| Item | Detail |
|---|---|
| Standard | DIN 931/ISO 4014 / EN ISO 4014 |
| Type | Partially threaded hex head bolt with unthreaded shank |
| Size Range | M6 – M64 |
| Thread | Metric coarse per ISO 261 (standard); fine thread per ISO 8676 on request |
| Thread Tolerance | 6g per ISO 965-1 |
| Product Grade | Grade A (M6 – M24); Grade B (M27 – M64) |
| Material | Carbon Steel / Alloy Steel / SS316 (A4-80) |
| Property Class | 4.8 / 8.8 / 10.9 / 12.9 (ISO 898-1); A2-70 / A4-70 / A4-80 (ISO 3506-1) |
| Surface Treatment | Plain (self-color) / HDG / Zinc plated / Dacromet / PTFE (Xylan) |
| Certification | EN 10204 3.1 material certificate provided as standard; third-party inspection available upon request |
| Packing | Bulk carton / Steel pallet / Custom labeling |
DIN 931 vs ISO 4014 — Standard Relationship
DIN 931 is the former German national standard for partially threaded hex bolts. ISO 4014 is the current international equivalent. Both standards are dimensionally identical except for four sizes where the width across flats (WAF) differs:
| Size | DIN 931 WAF (mm) | ISO 4014 WAF (mm) | Difference |
|---|---|---|---|
| M10 | 17 | 16 | DIN 17 → ISO 16 (−1 mm) |
| M12 | 19 | 18 | DIN 19 → ISO 18 (−1 mm) |
| M14 | 22 | 21 | DIN 22 → ISO 21 (−1 mm) |
| M22 | 32 | 34 | DIN 32 → ISO 34 (+2 mm) |
Procurement note: If your existing tooling is sized for DIN 931 dimensions (e.g., 17 mm socket for M10), switching to ISO 4014 bolts requires different sockets (16 mm). Always confirm which standard your drawing references before ordering. All other sizes from M6 to M64 (excluding M10, M12, M14, M22) have identical WAF in both standards.
Partial Thread (DIN 931) vs Full Thread (DIN 933) — When to Use Which
The choice between DIN 931 and DIN 933 affects joint behavior under load, not just bolt appearance.
| Feature | DIN 931 / ISO 4014 (Partial Thread) | DIN 933 / ISO 4017 (Full Thread) |
|---|---|---|
| Thread coverage | Partial — unthreaded shank under the head | Full — threads from under head to tip |
| Shear plane behavior | Smooth shank can cross shear plane; full cross-section bears load | Thread root at shear plane; ~20–25% lower effective shear area |
| Primary design case | Shear-dominated and combined shear + tension joints | Tension-dominated joints requiring full clamp force |
| Positioning function | Unthreaded shank acts as locating dowel | No dowel function; threads throughout |
| Stock availability | Common in 8.8 and 10.9; 12.9 often made to order | Deepest stock across all grades and sizes |
| Typical marine use | Engine mounts, crane pedestals, structural steel connections | Flange bolting, pipe clamp, general equipment assembly |
Design rule: In shear-critical joints, ensure the unthreaded shank length of the DIN 931 bolt is sufficient to span the full grip thickness so that no threads enter the shear plane. If the grip is too long relative to available bolt lengths, consider using a fitted bolt or reamed hole.
Thread Length Reference (per ISO 4014)
Thread length (b) depends on total bolt length (L). The table below covers the most commonly ordered size range:
| Size | Pitch (mm) | b: L ≤ 125 mm | b: 125 < L ≤ 200 mm | b: L > 200 mm |
|---|---|---|---|---|
| M6 | 1.0 | 18 | — | — |
| M8 | 1.25 | 22 | 28 | 41 |
| M10 | 1.5 | 26 | 32 | 45 |
| M12 | 1.75 | 30 | 36 | 49 |
| M16 | 2.0 | 38 | 44 | 57 |
| M20 | 2.5 | 46 | 52 | 65 |
| M24 | 3.0 | 54 | 60 | 73 |
| M30 | 3.5 | 66 | 72 | 85 |
| M36 | 4.0 | 78 | 84 | 97 |
| M42 | 4.5 | 90 | 96 | 109 |
| M48 | 5.0 | 102 | 108 | 121 |
Example: An M16 × 80 DIN 931 bolt has b = 38 mm thread length and 42 mm unthreaded shank (80 − 38 = 42 mm). The full cross-section of the 16 mm shank carries shear load in the grip zone.
Property Classes and Material Grades
| Property Class | Material | Tensile Strength | Yield Strength (0.2%) | Standard |
|---|---|---|---|---|
| 4.8 | Carbon steel (mild) | 400 MPa | — | ISO 898-1 |
| 8.8 | Carbon steel, quenched and tempered | 800 MPa | 640 MPa | ISO 898-1 |
| 10.9 | Alloy steel, quenched and tempered | 1040 MPa | 940 MPa | ISO 898-1 |
| 12.9 | Alloy steel, quenched and tempered | 1220 MPa | 1100 MPa | ISO 898-1 |
| A2-70 | SS304 austenitic stainless | 700 MPa | 450 MPa | ISO 3506-1 |
| A4-80 | SS316 austenitic stainless, cold worked | 800 MPa | 600 MPa | ISO 3506-1 |
For marine structural connections, 8.8 HDG is the most widely specified combination for above-water and engine room bolting. A4-80 SS316 is specified for direct seawater exposure zones (deck hardware, topside piping, ballast tank access). For sizes above M30, 10.9 is the most commonly available high-strength grade; 12.9 above M24 is typically made to order.
Hydrogen embrittlement warning: Property classes 10.9 and 12.9 subjected to electroplating or acidic pickling require hydrogen relief baking per ISO 9587 (220°C minimum, within 4 hours of plating) to prevent delayed brittle failure.
Marine Applications
DIN 931 partially threaded hex bolts are specified across marine and offshore structures where shear and dynamic loading dominate:
| Application Area | Typical Use | Common Specification |
|---|---|---|
| Engine Room | Engine mounting bolts, generator set foundation, pump baseplate anchoring | M16–M36, Grade 8.8 or 10.9, HDG or Dacromet |
| Hull Structure | Hull-to-frame connections, watertight door framing, structural steel splice joints | M20–M36, Grade 8.8, HDG |
| Deck Equipment | Crane pedestal bolting, winch base mounting, mooring equipment foundations | M20–M42, Grade 10.9, HDG or Dacromet |
| Offshore | Platform module connections, riser clamp bolting, jacket structural joints | M24–M48, Grade 10.9, Dacromet or PTFE |
| Seawater Exposure | Deck hardware, topside piping supports, navigation equipment mounting | M10–M30, A4-80 SS316 |
Quality Assurance
- EN 10204 3.1 material certificates provided as standard — chemical composition, tensile strength, hardness, proof load, all traceable to mill test reports
- Third-party inspection available upon request (SGS, BV, DNV surveyors)
- Can cooperate with classification society requirements for marine and offshore projects
- Annual production capacity: 50,000 tons
- Full standard coverage: DIN / ISO / EN / GB / ASTM / ANSI
Contact
Email:sales@sinofastener.com
Website:www.zlfastener.com
SINOFASTENER — Professional marine fastener supplier. Annual capacity 50,000 tons. Covering DIN/ISO/EN/GB/ASTM/ANSI standards. Material certificates traceable to mill. Third-party inspection available.
