Description
Overview
DIN 931 defines a hexagon head bolt with a partially threaded shank. The standard covers the dimensional form of the bolt, including the hex head, threaded portion and plain shank, so that the fastener can be selected consistently by diameter, length and thread. The partially threaded design is useful where the smooth shank should pass through the joint to improve alignment and carry shear loads, while the threaded section provides the clamping force.
This selected size is specified with diameter M8, length 40 mm, thread M8, pitch 1.25 mm.
Sold in multiples of '100 pieces. 1 Box = '100 pieces.
Material, Grade & Strength
A4 stainless steel, commonly associated with 316 stainless, is selected for improved corrosion resistance in aggressive environments such as coastal, chemical and outdoor exposure. A4 stainless is corrosion resistant rather than high tensile in the same sense as carbon steel property classes; where strength is critical, use the appropriate stainless property class and torque guidance.
Finish & Corrosion Protection
Stainless products rely on the corrosion resistance of the stainless material itself rather than a separate plated coating.
Typical Uses
DIN 931 bolts are commonly used in machinery, fabricated steelwork, mining equipment, agricultural equipment, brackets, frames and maintenance work where a strong partially threaded bolt is preferred over a fully threaded set screw.
Technical Tips
- Use a matching nut and washer of the same thread size and suitable strength class.
- Where possible, position the plain shank through the shear plane of the joint rather than leaving threads in the shear area.
- For Grade 8.8, 10.9 or 12.9 bolts, use correctly rated mating nuts and washers.
- Torque values vary by diameter, pitch, finish and lubrication; always confirm the correct torque before use in safety-critical assemblies.
- For corrosion-sensitive applications, match the finish or material to the environment rather than relying only on strength grade.
Selection Advice
Choose DIN 931 when the joint benefits from a partially threaded shank. Choose DIN 933 when a fully threaded hexagon head set screw is required. Confirm diameter, length, thread, material, finish and grade before ordering.
Frequently Asked Questions
What is the difference between DIN 931 and DIN 933? DIN 931 is partially threaded, while DIN 933 is fully threaded. DIN 931 is often preferred where the plain shank assists alignment or shear performance.
Is Grade 8.8 stainless steel? No. Grade 8.8 normally refers to high tensile carbon-alloy steel. Stainless fasteners are usually specified by A2, A4 or a stainless property class.
Dimensions – DIN 931 / ISO 4014 M8 x 40
| Standard | DIN 931 / ISO 4014 |
|---|---|
| Product | Hexagon head bolt, part thread |
| Thread | M8 x 1.25 |
| Length (l) | 40 mm |
| Across flats (s) | 13 mm |
| Head height (k) | 5.5 mm |
| Thread length (b) | 22 mm (ref.) |
| Stress area (As) | 36.6 mm² |
| Weight (calculated) | 20.39 kg per 1 000 pieces |
Material, Grade & Strength
| Material | Stainless steel A4 (316) |
|---|---|
| Steel grade | AISI 316 (1.4401) |
| Composition | C max 0.07%, Cr 16.5-18.5%, Ni 10.0-13.0%, Mo 2.0-2.5% |
| Property class | A4-70 (ISO 3506) unless marked -80 |
| Tensile strength Rm (min) | 700 MPa (class 70), 800 MPa (class 80) |
| Yield Rp0.2 (min) | 450 MPa (class 70), 600 MPa (class 80) |
| Typical use | marine, coastal, chlorides, chemical plant |
Finish & Corrosion Protection
Plain / self colour: No applied coating. Stainless, brass and nylon parts are supplied plain; plain steel parts need oil, paint or protected environments.
DIN 931 data sheet – all sizes
| Size | Thread | Across flats (s) | Head height (k) | Thread length (b) | Stress area (As) |
|---|---|---|---|---|---|
| M3 | M3 x 0.5 | 5.5 mm | 2 mm | 12 mm (ref.) | 5.0 mm² |
| M4 | M4 x 0.7 | 7 mm | 2.8 mm | 14 mm (ref.) | 8.8 mm² |
| M5 | M5 x 0.8 | 8 mm | 3.5 mm | 16 mm (ref.) | 14.2 mm² |
| M6 | M6 x 1 | 10 mm | 4 mm | 18 mm (ref.) | 20.1 mm² |
| M7 | M7 x 1 | 11 mm | 4.8 mm | 20 mm (ref.) | 28.9 mm² |
| M8 | M8 x 1.25 | 13 mm | 5.5 mm | 22 mm (ref.) | 36.6 mm² |
| M10 | M10 x 1.5 | 17 mm (ISO: 16 mm) | 7 mm | 26 mm (ref.) | 58.0 mm² |
| M12 | M12 x 1.75 | 19 mm (ISO: 18 mm) | 8 mm | 30 mm (ref.) | 84.3 mm² |
| M14 | M14 x 2 | 22 mm (ISO: 21 mm) | 9 mm | 40 mm (ref.) | 115.4 mm² |
| M16 | M16 x 2 | 24 mm | 10 mm | 44 mm (ref.) | 156.7 mm² |
| M18 | M18 x 2.5 | 27 mm | 12 mm | 48 mm (ref.) | 192.5 mm² |
| M20 | M20 x 2.5 | 30 mm | 13 mm | 52 mm (ref.) | 244.8 mm² |
| M22 | M22 x 2.5 | 32 mm (ISO: 34 mm) | 14 mm | 69 mm (ref.) | 303.4 mm² |
| M24 | M24 x 3 | 36 mm | 15 mm | 73 mm (ref.) | 352.5 mm² |
| M27 | M27 x 3 | 41 mm | 17 mm | 79 mm (ref.) | 459.4 mm² |
| M30 | M30 x 3.5 | 46 mm | 19 mm | 85 mm (ref.) | 560.6 mm² |
| M33 | M33 x 3.5 | 50 mm | 21 mm | 91 mm (ref.) | 693.6 mm² |
| M36 | M36 x 4 | 55 mm | 23 mm | 97 mm (ref.) | 816.7 mm² |
| M39 | M39 x 4 | 60 mm | 25 mm | 103 mm (ref.) | 975.8 mm² |
| M42 | M42 x 4.5 | 65 mm | 26 mm | 109 mm (ref.) | 1120.9 mm² |
| M45 | M45 x 4.5 | 70 mm | 28 mm | 115 mm (ref.) | 1306.0 mm² |
| M48 | M48 x 5 | 75 mm | 30 mm | 121 mm (ref.) | 1473.1 mm² |
| M52 | M52 x 5 | 80 mm | 33 mm | 129 mm (ref.) | 1757.8 mm² |
| M56 | M56 x 5.5 | 85 mm | 35 mm | 137 mm (ref.) | 2030.0 mm² |
| M60 | M60 x 5.5 | 90 mm | 38 mm | 145 mm (ref.) | 2362.0 mm² |
| M64 | M64 x 6 | 95 mm | 40 mm | 153 mm (ref.) | 2676.0 mm² |
Nominal dimensions per DIN 931 / ISO 4014. Weights are calculated from nominal dimensions and are a guide only (±10%). Values for fit and strength should be confirmed against the standard for critical applications.
Specifications
| Measurement Type | Metric |
|---|---|
| Thread Size | M8 |
| Thread Pitch | 1.25 mm |
| Thread Style | Partial Thread |
| Drive Size | 13 mm |
| Drive Type | External Hex |
| Head Style | Hex |
| Diameter | M8 |
| Length | 40 mm |
| Material | Stainless Steel |
| Finish | Stainless steel |
| Grade | Grade (A4) |
| Standards Met | DIN 931 |
| Package Quantity | 100 |
| Package Type | Box |