Socket-Head Counterbore
Counterbore dimensions for socket-head cap screws (ISO 4762 / DIN 912). Counterbore diameter clears the head with a little margin; depth just buries the head.
| Screw | Head dia | Clearance hole | C-bore dia | C-bore depth |
|---|---|---|---|---|
| M3 | 5.5 | 3.4 | 6.5 | 3.4 |
| M4 | 7 | 4.5 | 8 | 4.4 |
| M5 | 8.5 | 5.5 | 9.75 | 5.4 |
| M6 | 10 | 6.6 | 11.25 | 6.4 |
| M8 | 13 | 9 | 14.5 | 8.4 |
| M10 | 16 | 11 | 17.5 | 10.5 |
| M12 | 18 | 13.5 | 19.5 | 12.5 |
| M16 | 24 | 17.5 | 25.5 | 16.5 |
| M20 | 30 | 22 | 31.5 | 20.5 |
All values in mm (normal-series clearance). For a flush head add ~0.5 mm depth.
A reference aid, not a substitute for engineering judgment. Verify against the governing standard.