Countersink Diameter and Cutting Depth

The print gives the finished countersink diameter, but the machine is set to a plunge depth, Z = (D_cs - d_hole) / (2 tan(angle/2)). A 0.500 in countersink, 82 deg inch head, 0.250 in pilot hole needs 0.1438 in of plunge; the same diameter with a 60 deg tool needs 0.2165 in -- a shallower angle drives the tool half again as deep, so the angle callout matters as much as the diameter. 82 deg (inch flat-head) and 90 deg (metric) are NOT interchangeable -- mismatched screw and sink never seat flush, and a few thousandths of over-plunge sits a flat-head proud or buried. A setup aid; the tool geometry and the fastener callout govern.

Z = (D_cs - d_hole) / (2 x tan(angle/2)); Z_full = D_cs / (2 x tan(angle/2)).

Countersink diameter-to-depth relation (Machinery's Handbook countersinking; 82 deg inch and 90 deg metric flat-head standards), first-principles trigonometry, by name; the tool geometry and the fastener callout govern.

The countersink diameter-to-depth relation is first-principles cone trigonometry; the diameter, angle, and pilot hole come from the print and the tool.

Estimate. AHJ and licensed professional govern.

Field names used by the API: countersink_dia_in, included_angle_deg, pilot_hole_dia_in, z_in

• Diameter to depth the machine is set to a depth to produce the diameter the print calls outMachinery's Handbook
• Angle standard 82 deg inch flat-head and 90 deg metric are not interchangeableflat-head fastener standards
• Angle drives depth a shallower included angle plunges deeper for the same diametercone geometry