Really? So on, say, a 3/4” drill you only really need roughly a 1/4” pilot? Or less?
Recognize this is only from the perspective of web clearance. A 90-deg pilot hole edge is not a great way to ensure centering accuracy. That's why we try to choose a center drill with ideally same angle as the drill itself. Which then begs the question - so how do I then drill progressively from .25 to 1.00 because there will be lots of intermediate 90-deg holes without the lip angle to mate to the next drill? Nobody really talks about that but the answers I'm aware of are
- pre-chamfer the hole so the lip matches the drill angle of next (which is kind of a pita unless you have big 118 or 120 deg countersinks)
- you accept that hole drilling is a roughing operation mostly intending to remove material & you will correct the final hole with a boring operation
- possibly replace the successive drilling with annular cutters or similar & take the big lump out in one operation