DIN 931 Hexagon Head Bolt (Half thread)
Equivalent Standard:
IS 4014 | UNI 5737 | EU 24014
DIN 931 is the German standard for hexagon head bolts with partial( Half) thread, widely used in mechanical engineering and construction.
These bolts feature:
- Hexagonal head for wrench tightening
- Partially threaded shank (thread length ≈ 2d + 6mm)
- Metric coarse thread (standard) or fine thread (DIN 933).
Other International Equivalent Standards for DIN 931
- DIN 931: Original German standard
- ISO 4014: International equivalent (partial thread)
- EN 24014: European harmonized version
- ASTM A325M US Standard
The bolts are designed with a partially threaded shank, which provides a secure and stable connection when inserted into a pre-tapped hole or paired with a nut.
Application
DIN 931 hexagon head bolts with shank are widely used across various industries for heavy-duty fixing applications, including:
- Construction (e.g., structural Steel framing)
- Machinery and equipment manufacturing
- Automotive Components
- Railway equipment
- Electric motors and engines
- Infrastructure systems (e.g., bridges, water treatment plants)
- wind Energy
- Industrial equipment
- When shear strength is critical (unthreaded portion resists shear)
DIN 931 hex head bolts provide reliable and robust fastening solutions that can withstand high loads and resist loosening under extreme conditions.
Surface Treatments
Type
Corrosion Resistance
Appearance
Plain (black oxide)
Basic
Matte black
Zinc-plated
Moderate
Shiny silver
Hot-dip galvanized
High
Dull gray
Dacromet
Excellent
Gray/silver
DIN 931
DIN 931 is a German Industrial Standard (Deutsches Institut für Normung) that specifies requirements for hexagon head bolts with a partial thread (shank). These bolts are commonly referred to as “Hexagon Cap Screws Partially Threaded Bolts” or “Hex Head Bolts with Shank.”
Hexagon Head: The bolt features a hexagonal head, designed for tightening with a spanner or socket tool.
Partial Thread (Shank): Unlike DIN 933 fully threaded Hex bolts, DIN 931 Hex Bolts have a smooth, unthreaded portion (shank) below the head before the thread begins. This shank provides greater shear strength and can be beneficial in applications where bending forces are present or where precise alignment is needed through a clearance hole.
Mating: They are typically used with a nut or within a pre-tapped hole.
Comparison Between: DIN 931 vs DIN 933
Feature | DIN 931 | DIN 933 |
Thread | Partial | Full |
Use Case | Where unthreaded shank needed | Fully threaded applications |
Length Calculation | Total length includes head | Length measured under head |
DIN 931 Standard is superseded by ISO 4014.
DIN 931 Hex Bolt(and its equivalent ISO 4014) specifies a partially threaded hex bolt, offering a balance of strength, ease of use, and versatility for many mechanical and structural fastening needs.
- DIN 931 bolts are manufactured from various Steel Grade materials:
- 5.6: General purpose steel.
- 8.8: High tensile steel, very common for structural and general engineering applications.
- 10.9: Higher tensile steel for demanding applications.
- 12.9: Very high tensile steel for critical and heavy-duty applications.
Technical Specification for Hexagon Head Bolts With Shank (DIN 931)
| Size | Width Across Flat (s) | Head Height (k) | Thread Length | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DIN 931 | ISO 4014 | DIN 931 | ISO 4014 | DIN 931 Length (in MM) | ISO 4014 Length (in MM) | |||||||||
| Min | Max | Min | Max | Min | Max | Min | Max | ≥125 | >125≥200 | ≥200 | ≥125 | >125≥200 | ≥200 | |
| M2 | 3.82 | 4.00 | 3.82 | 4.00 | 1.28 | 1.52 | 1.275 | 1.525 | 10 | – | – | 10 | – | – |
| M3 | 5.32 | 5.50 | 5.32 | 5.50 | 1.88 | 2.12 | 1.875 | 2.125 | 12 | – | – | 12 | – | – |
| M4 | 6.78 | 7.00 | 6.78 | 7.00 | 2.68 | 2.92 | 2.675 | 2.925 | 14 | – | – | 14 | – | – |
| M5 | 7.78 | 8.00 | 7.78 | 8.00 | 3.35 | 3.65 | 3.35 | 3.65 | 16 | 22 | – | 16 | – | – |
| M6 | 9.78 | 10.00 | 9.78 | 10.00 | 3.85 | 4.15 | 3.85 | 4.15 | 18 | 24 | – | 18 | – | – |
| M8 | 12.73 | 13.00 | 12.73 | 13.00 | 5.15 | 5.45 | 5.15 | 5.45 | 22 | 28 | 41 | 22 | – | – |
| M10 | 16.73 | 17.00 | 15.73 | 16.00 | 6.22 | 6.58 | 6.22 | 6.58 | 26 | 32 | 45 | 26 | – | – |
| M12 | 18.67 | 19.00 | 17.73 | 18.00 | 7.32 | 7.68 | 7.32 | 7.68 | 30 | 36 | 49 | 30 | – | – |
| M14 | 21.67 | 22.00 | 20.67 | 21.00 | 8.62 | 8.98 | 8.62 | 8.98 | 34 | 40 | 53 | 34 | 40 | – |
| M16 | 23.67 | 24.00 | 23.67 | 24.00 | 9.82 | 10.2 | 9.82 | 10.18 | 38 | 44 | 57 | 38 | 44 | – |
| M18 | 26.67 | 27.00 | 26.67 | 27.00 | 11.28 | 11.7 | 11.285 | 11.715 | 42 | 48 | 61 | 42 | 48 | – |
| M20 | 29.67 | 30.00 | 29.67 | 30.00 | 12.28 | 12.7 | 12.285 | 12.715 | 46 | 52 | 65 | 46 | 52 | – |
| M22 | 31.61 | 32.00 | 33.38 | 34.00 | 13.78 | 14.2 | 13.785 | 14.215 | 50 | 56 | 69 | 50 | 56 | 69 |
| M24 | 35.38 | 36.00 | 35.38 | 36.00 | 14.78 | 15.2 | 14.785 | 15.215 | 54 | 60 | 73 | 54 | 60 | 73 |
| M27 | 40.00 | 41.00 | 40.00 | 41.00 | 16.65 | 17.4 | 16.65 | 17.35 | 60 | 66 | 79 | 60 | 66 | 79 |
| M30 | 45.00 | 46.00 | 45.00 | 46.00 | 18.28 | 19.1 | 18.28 | 19.12 | 66 | 72 | 85 | 66 | 72 | 85 |
| M33 | 49.00 | 50.00 | 49.00 | 50.00 | 20.58 | 21.4 | 20.58 | 21.42 | 72 | 78 | 91 | – | 78 | 91 |
| M36 | 53.80 | 55.00 | 53.80 | 55.00 | 22.08 | 22.9 | 22.08 | 22.92 | 78 | 84 | 97 | – | 84 | 97 |
| M39 | 58.80 | 60.00 | 58.80 | 60.00 | 24.58 | 25.4 | 24.58 | 25.42 | 84 | 90 | 103 | – | 90 | 103 |
| M42 | 63.10 | 65.00 | 63.10 | 65.00 | 25.58 | 26.4 | 25.58 | 26.42 | 90 | 96 | 109 | – | 96 | 109 |
| M45 | 68.10 | 70.00 | 68.10 | 70.00 | 27.58 | 28.4 | 27.58 | 28.42 | 96 | 102 | 115 | – | 102 | 115 |
| M48 | 73.10 | 75.00 | 73.10 | 75.00 | 29.58 | 30.4 | 29.58 | 30.42 | 102 | 108 | 121 | – | 108 | 121 |
| M52 | 78.10 | 80.00 | 78.10 | 80.00 | 32.5 | 33.5 | 32.5 | 33.5 | – | 116 | 129 | – | 116 | 129 |
| M56 | 82.80 | 85.00 | 82.80 | 85.00 | 34.5 | 35.5 | 34.5 | 35.5 | – | 124 | 137 | – | – | 137 |
| M60 | 87.80 | 90.00 | 87.80 | 90.00 | 37.5 | 38.5 | 37.5 | 38.5 | – | 132 | 145 | – | – | 145 |
| M64 | 92.80 | 95.00 | 92.80 | 95.00 | 39.5 | 40.5 | 39.5 | 40.5 | – | 140 | 153 | – | – | 153 |
| M72 | 102.80 | 105.00 | — | — | 44.5 | 45.5 | — | — | – | 156 | 169 | – | – | – |