Estimate hole diameter and countersink depth from bolt size, radial fit, countersink angle, and countersink diameter.
| Hole | – |
| Countersink depth | – |
Use this calculator to drill a clearance hole and a conical countersink. Enter the bolt diameter, the radial fit each side, the included countersink angle, and the countersink face diameter.
Hole = bolt + 2 × fit. Depth = (countersink diameter − hole) / 2 / tan(angle ÷ 2), or 0 if the angle is 0. Bolt, fit, and countersink diameter can be entered in millimetres (mm) or inches (in). Hole and depth follow the same unit. Angle is in degrees.
This is a geometric cone. It does not add a drill-size table or a head-style standard.
Bolt: Shank diameter, in mm or in.
Fit: Radial clearance each side, in mm or in.
Countersink angle (°): Included angle of the cone, often 90° or 82°.
Countersink diameter: Face diameter of the countersink, in mm or in.
Hole: Clearance-hole diameter.
Countersink depth: Depth of the cone.
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