How to Use Countersink Depth Calculator
The Countersink Depth Calculator answers a recurring CNC and shop-floor question: “how far do I plunge?”
- Pick a unit — mm or inch.
- Enter chamfer diameter D and pilot hole d — Match the screw head profile and tap drill.
- Enter the included angle — 82°, 90°, 100° or any custom value.
- Read the result — Plunge depth, slant length and chamfer width.
Formula & Theory — Countersink Depth Calculator
The Countersink Depth Calculator is based on a simple cone:
depth = (D - d) / (2 × tan(angle / 2))
slant length = (D - d) / (2 × sin(angle / 2))
chamfer width = (D - d) / 2| Symbol | Meaning |
|---|---|
| D | Final chamfer diameter (head flush) |
| d | Pilot / clearance hole diameter |
| angle | Included countersink angle |
Tip vs head reference
The depth reported by the Countersink Depth Calculator is measured from the surface to where the cone meets the pilot hole. For a flat-bottom CNC reference, add the cone tip allowance from the tool.
Use Cases for Countersink Depth Calculator
- CNC programming — Convert a chamfer diameter callout to a plunge Z depth.
- Sheet metal — Size countersinks for flush fastener finishes.
- Furniture and joinery — Recess screw heads cleanly into hardwood.
- Aerospace inspection — Verify that as-machined countersinks fit fastener gauges.
- Repair and rework — Calculate touch-up depth when refinishing an existing chamfer.
- Education — Teach the connection between cone geometry and tool depth.
The Countersink Depth Calculator removes a common source of programming error in production.