Calculators
Counterbore Calculator
Pick a socket head cap screw and get its head dimensions plus a recommended counterbore diameter and minimum depth so the head seats below flush — inch or metric.
Last verified: 2026-07-09
A counterbore is a flat-bottomed recess that lets a socket head cap screw sit below the surface. Choose the screw and a clearance to get the counterbore diameter (clears the head) and minimum depth (at least the head height).
Screw system
Head Ø
10mm
Head height
6mm
Counterbore Ø
10.5mm
Min depth
6.5mm
Head dimensions are the standard ISO 4762 values. The counterbore must clear the head Ø and be at least head-height deep; the clearance you add sets how far below flush the head sits. Hex key: 5 mm.
Frequently asked
- How much clearance should I add?
- Enough to clear the head diameter and drop the head below flush — a small allowance (a fraction of a millimetre, or a few thousandths of an inch) is typical. Standard counterbore tooling comes in set sizes; pick the next size up from the head diameter.
Sources
- Socket head cap screw head dimensions per ASME B18.3 / ISO 4762