Countersink Depth Calculator
Major diameter and plunge depth so a flat-head screw sits flush — head diameter, pilot hole, included angle and a seating allowance.
Program the countersink by DEPTH, not by eye: with a 90° tool every 0.1 mm of plunge adds exactly 0.2 mm of diameter, which is why hand-fed countersinks always end up oversize and chattered. Match the angle to the screw standard first — burying a 90° metric head in an 82° inch countersink leaves it riding on its rim, proud of the surface, and stripping the recess when torqued.
Formula
Major diameter and plunge depth so a flat-head screw sits flush — head diameter, pilot hole, included angle and a seating allowance. A free machinist & fabrication essentials tool — no sign-up, no upload, instant results in your browser.
About Countersink Depth Calculator
Countersink Depth Calculator computes the governing relationship Ø_csk = Ø_head + allowance ; depth = (Ø_csk − Ø_pilot) / (2·tan(θ/2)) live as you type. Program the countersink by DEPTH, not by eye: with a 90° tool every 0.1 mm of plunge adds exactly 0.2 mm of diameter, which is why hand-fed countersinks always end up oversize and chattered. Match the angle to the screw standard first — burying a 90° metric head in an 82° inch countersink leaves it riding on its rim, proud of the surface, and stripping the recess when torqued. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Countersink Depth Calculator
- 1Enter your values — Screw head diameter, Pilot / clearance hole Ø, Included angle, Diameter allowance (sensible defaults are pre-filled).
- 2Read the live results: Countersink major Ø, Plunge depth from surface.
- 3Check the "with your numbers" line to see Ø_csk = Ø_head + allowance ; depth = (Ø_csk − Ø_pilot) / (2·tan(θ/2)) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Countersink Depth Calculator?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula Ø_csk = Ø_head + allowance ; depth = (Ø_csk − Ø_pilot) / (2·tan(θ/2)) with authoritative sources cited on the page (ISO 10642 / DIN 74 — Countersunk head screws and countersinks; Machinery's Handbook, 31st ed.)
- ✓Program the countersink by DEPTH, not by eye: with a 90° tool every 0.1 mm of plunge adds exactly 0.2 mm of diameter, which is why hand-fed countersinks always end up oversize and chattered.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the countersink depth calculator use?+
It evaluates Ø_csk = Ø_head + allowance ; depth = (Ø_csk − Ø_pilot) / (2·tan(θ/2)), exactly as published. Sources: ISO 10642 / DIN 74 — Countersunk head screws and countersinks; Machinery's Handbook, 31st ed.. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
Program the countersink by DEPTH, not by eye: with a 90° tool every 0.1 mm of plunge adds exactly 0.2 mm of diameter, which is why hand-fed countersinks always end up oversize and chattered. Treat the output as a planning estimate and verify against the governing documents for your project.
When is this calculator the right tool for the job?+
Major diameter and plunge depth so a flat-head screw sits flush. Match the angle to the screw standard first — burying a 90° metric head in an 82° inch countersink leaves it riding on its rim, proud of the surface, and stripping the recess when torqued. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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