Countersink Diameter Depth Calculator
Countersink diameter-depth searches usually need the depth from a desired rim diameter, not a generic Z move from the tool tip. Use the countersink calculator to solve axial depth from included angle, top diameter and existing hole diameter.
Diameter-to-depth formula
z = (D_top - D_hole) / (2 * tan(A / 2))
Cutting into solid
When there is no pilot hole, set D_hole = 0. The same cone formula then gives depth from the desired top diameter and included angle.
z = D_top / (2 * tan(A / 2))
Chamfer width
Chamfer width along the cone face is longer than axial depth because it follows the sloped surface.
w = (D_top - D_hole) / (2 * sin(A / 2))
Machine-depth caution
The calculator depth is measured from the work surface or pilot-hole rim. Tool-tip Z depth can differ when the countersink has a pilot, point flat, damaged tip or nonconical geometry.
Frequently asked questions
How do I calculate countersink depth from diameter?
Use z = (D_top - D_hole) / (2 * tan(A / 2)), where A is the included countersink angle, D_top is the rim diameter and D_hole is the existing hole diameter.
What if I am countersinking into solid stock?
Set the existing hole diameter to 0. A 90 degree cone then reaches a 10 mm rim at 5 mm axial depth.
Related pages
- Countersink depth calculator - live diameter, angle and chamfer-width calculator.
- Drill point length calculator - twist-drill point allowance for blind holes.
- Tap drill size calculator - tap-hole diameter and thread engagement.
- Thread pitch chart - pitch reference for nearby threaded-hole work.