Fasteners & Drilling
Metric Bolt Head & Socket Sizes
Across-flats (A/F) dimensions for standard hex bolt heads, and hex key size for socket head cap screws, for common metric bolt sizes.
| Bolt Size | Hex Head A/F | Socket Head Hex Key |
|---|---|---|
| M3 | 5.5 | 2.5 |
| M4 | 7 | 3 |
| M5 | 8 | 4 |
| M6 | 10 | 5 |
| M8 | 13 | 6 |
| M10 | 17 | 8 |
| M12 | 19 | 10 |
| M16 | 24 | 14 |
| M20 | 30 | 17 |
Reference values only. Verify against the current governing standard (e.g. ISO, ANSI, ASME, DIN) before using in production drawings or manufacturing. Provided by Micro Components as a free engineering resource.
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