Here is a technique without measurement, tables or calipers, that works on any drill press and gets just as close on the first pass as the original. It still uses a gauge but it’s just the screw itself lightly held upside down in the drill chuck. If the periphery of the screw head is quite sharp, a scriber can be used for marking. Otherwise, I find that the thickness of the pencil lead helps to compensate for the head edge flattening.
Drill a pilot hole
Mark the Perimeter
Countersink to the Mark
Check the Fit
It usually takes me more than one stroke to get a perfect countersink because of the inherent limitations in the gauging process. This is the best I’ve been able to do. If anybody out there has a better technique, I’d sure love to hear about it.
