DIN 931 Hex Head Bolts
We supply DIN 931 part-threaded hex head bolts in high tensile steel grades 8.8, 10.9 and 12.9 and stainless steel A2 and A4, from M4 to M48. The plain shank below the head locates the joint and carries shear better than a fully threaded fastener, which makes DIN 931 the default bolt for structural and machinery joints where the joint plane falls on the shank.
Also known as: hex bolt, hexagon head bolt, part threaded bolt, hexagon bolt, HT bolt.
DIN 931 dimensions
| Diameter | Pitch | Thread length (b)¹ | Head depth (k) | Across flats (s) |
|---|---|---|---|---|
| M4 | 0.7 mm | 14 mm | 2.8 mm | 7 mm |
| M5 | 0.8 mm | 16 mm | 3.5 mm | 8 mm |
| M6 | 1.0 mm | 18 mm | 4.0 mm | 10 mm |
| M7 | 1.0 mm | 20 mm | 4.8 mm | 11 mm |
| M8 | 1.25 mm | 22 mm | 5.3 mm | 13 mm |
| M10 | 1.5 mm | 26 mm | 6.4 mm | 17 mm |
| M12 | 1.75 mm | 30 mm | 7.5 mm | 19 mm |
| M14 | 2.0 mm | 34 mm | 8.8 mm | 22 mm |
| M16 | 2.0 mm | 38 mm | 10 mm | 24 mm |
| M18 | 2.5 mm | 42 mm | 11.5 mm | 27 mm |
| M20 | 2.5 mm | 46 mm | 12.5 mm | 30 mm |
| M22 | 2.5 mm | 50 mm | 14 mm | 32 mm |
| M24 | 3.0 mm | 54 mm | 15 mm | 36 mm |
| M27 | 3.0 mm | 60 mm | 17 mm | 41 mm |
| M30 | 3.5 mm | 66 mm | 18.7 mm | 46 mm |
| M33 | 3.5 mm | 72 mm | 21 mm | 50 mm |
| M36 | 4.0 mm | 78 mm | 22.5 mm | 55 mm |
| M39 | 4.0 mm | 84 mm | 25 mm | 60 mm |
| M42 | 4.5 mm | 90 mm | 26 mm | 65 mm |
| M45 | 4.5 mm | 96 mm | 28 mm | 70 mm |
| M48 | 5.0 mm | 102 mm | 30 mm | 75 mm |
- Thread lengths are a guide for bolts under 125mm. For bolts over 125mm and up to 200mm add 6mm; for bolts 200mm and longer add 19mm.
Materials & strength
Steel grades 8.8, 10.9 & 12.9
Property class 8.8 (minimum tensile strength 800 N/mm2) covers most general and structural work; 10.9 and 12.9 give progressively higher clamp loads for machinery and high-duty joints.
Stainless A2 & A4
Supplied in grades 50, 70 and 80. A2 suits general and internal use; A4 adds molybdenum for marine and chemical environments.
Related specificationsWhat is the difference between DIN 931 and DIN 933?
DIN 931 is part threaded - a plain shank runs from the head to the thread - while DIN 933 is threaded along its full length. Choose DIN 931 where the joint plane should bear on the plain shank; choose DIN 933 where you need thread right up to the head.
Is DIN 931 the same as ISO 4014?
DIN 931 and ISO 4014 both cover part-threaded hexagon head bolts, but they should not be assumed to be dimensionally identical — across-flats dimensions differ at several sizes. If your drawing specifies one designation, send us the requirement and we can identify the appropriate product.
What materials are DIN 931 hex bolts available in?
DIN 931 hex bolts are available in high tensile steel grades 8.8, 10.9 and 12.9 and in A2 and A4 stainless steel across a wide range of metric sizes. Imperial-thread stainless hex bolts (UNC) are also supplied - tell us the size, grade and quantity.
Need DIN 931 in a non-standard size or material?
Send us your drawing — specials quoted within 24 hours.