Metric socket head cap screws (also known as Allen head screws) are precision fasteners. These fasteners are characterized by their cylindrical head with a recessed hexagonal socket, which allows for high torque application in confined spaces where traditional external drive screws cannot be used. The table provides standard dimensions for metric socket head cap screws according to ISO specifications. All measurements are shown in millimeters (mm). The size designation (e.g., M8 × 1.25) indicates the nominal thread diameter followed by the thread pitch.
Key dimensions included in the table are body diameter, head diameter, head height, chamfer/radius measurements, hex socket size, key engagement depth, and transition diameter. These specifications are critical for proper selection, installation, and replacement of metric fasteners in various applications. This reference chart covers common sizes ranging from M1.6 to M48, with both their maximum and minimum tolerance values to ensure proper fit and function in precision applications.
| Nominal Size | Body Dia D Max | Body Dia D Min | Head Dia A Max | Head Dia A Min | Head Height H Max | Head Height H Min | Chamfer/ Radius S Max | Hex Socket J Nom | Key Engage T Min | Trans Dia B Max |
|---|---|---|---|---|---|---|---|---|---|---|
| M1.6 × 0.35 | 1.60 | 1.58 | 3.00 | 2.86 | 1.60 | 1.52 | 0.18 | 1.5 | 0.7 | 1.6 |
| M2 × 0.4 | 2.00 | 1.98 | 3.80 | 3.65 | 2.00 | 1.86 | 0.20 | 1.5 | 1.0 | 2.0 |
| M2.5 × 0.45 | 2.50 | 2.48 | 4.50 | 4.35 | 2.50 | 2.35 | 0.25 | 2.0 | 1.1 | 2.5 |
| M3 × 0.5 | 3.00 | 2.98 | 5.50 | 5.32 | 3.00 | 2.82 | 0.30 | 2.5 | 1.3 | 3.0 |
| M4 × 0.7 | 4.00 | 3.97 | 7.00 | 6.81 | 4.00 | 3.82 | 0.40 | 3.0 | 1.8 | 4.0 |
| M5 × 0.8 | 5.00 | 4.97 | 8.50 | 8.29 | 5.00 | 4.82 | 0.50 | 4.0 | 2.3 | 5.0 |
| M6 × 1.0 | 6.00 | 5.96 | 10.00 | 9.78 | 6.00 | 5.82 | 0.60 | 5.0 | 2.5 | 6.0 |
| M8 × 1.25 | 8.00 | 7.96 | 13.00 | 12.73 | 8.00 | 7.78 | 0.80 | 6.0 | 3.5 | 8.0 |
| M10 × 1.5 | 10.00 | 9.95 | 16.00 | 15.73 | 10.00 | 9.78 | 1.00 | 8.0 | 4.4 | 10.0 |
| M12 × 1.75 | 12.00 | 11.95 | 18.00 | 17.73 | 12.00 | 11.73 | 1.20 | 10.0 | 5.3 | 12.0 |
| M14 × 2.0 | 14.00 | 13.93 | 21.00 | 20.67 | 14.00 | 13.73 | 1.40 | 12.0 | 6.2 | 14.0 |
| M16 × 2.0 | 16.00 | 15.93 | 24.00 | 23.67 | 16.00 | 15.73 | 1.60 | 14.0 | 7.1 | 16.0 |
| M20 × 2.5 | 20.00 | 19.90 | 30.00 | 29.67 | 20.00 | 19.48 | 2.00 | 17.0 | 8.8 | 20.0 |
| M24 × 3.0 | 24.00 | 23.90 | 36.00 | 35.38 | 24.00 | 23.48 | 2.40 | 19.0 | 10.3 | 24.0 |
| M30 × 3.5 | 30.00 | 29.90 | 45.00 | 44.38 | 30.00 | 29.48 | 3.00 | 22.0 | 12.7 | 30.0 |
| M36 × 4.0 | 36.00 | 35.88 | 54.00 | 53.12 | 36.00 | 35.38 | 3.60 | 27.0 | 15.4 | 36.0 |
| M42 × 4.5 | 42.00 | 41.88 | 63.00 | 62.12 | 42.00 | 41.38 | 4.20 | 32.0 | 17.9 | 42.0 |
| M48 × 5.0 | 48.00 | 47.85 | 72.00 | 71.10 | 48.00 | 47.35 | 4.80 | 36.0 | 20.6 | 48.0 |
Conclusion
We hope you found this article and table of value for your project and engineering needs. MISUMI USA carries a vast array of fasteners, and socket head cap screws. We also have several articles and tables related to fasteners that you might find helpful including external screw thread size. Please contact our engineers and product specialists with any questions you have about the best socket head cap screw for your next project.
Author: Scott Bredemann | Updated: 4/14/2025
Disclaimer:
The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements