How this calculator works
An axial section through the cone gives two right triangles. Half the diameter increase is the radial leg and the countersink depth is the axial leg. This ideal geometry excludes tool-tip flats, runout and clearance allowances.
Formula
h = (D - d) / [2 tan(theta/2)]; D = d + 2h tan(theta/2); theta = 2 atan[(D-d)/(2h)].
Worked example
A 10 mm mouth over a 5 mm pilot with a 90 degree included angle needs (10-5)/2 = 2.5 mm depth.
Advertisement
Frequently asked questions
Should I enter 45 or 90 degrees?
Enter the full included angle between opposite conical faces, such as 90 degrees for a 90 degree countersink.
What if I need the full cone height?
Set the pilot diameter to zero.
Does this guarantee a flush screw?
No. Confirm the actual fastener head profile, tolerances and seating requirements.