How to Choose Pilot Hole Depth and Diameter
Why Pilot Hole Geometry Matters The pilot hole is the only thing guiding the gun drill during the first few millimeters of entry. If the pilot geometry is wrong, the drill starts off-center or at an angle, and the rest of the hole follows that bad start. I have measured the effect of pilot geometry on hole straightness across dozens of jobs. A pilot hole that is 0.1mm oversized produces a starting hole that is 0.05-0.08mm oversized at entry and the error propagates as the drill goes deeper. ...