The characteristic of the single flute gundrilling process is that coolant is fed through the coolant hole in the tool and exits along with the chips in the V-shaped groove (flute) on the drill tube from the drilled hole. The coolant also provides lubrication to the drill periphery.
This is possible if coolant, i.e. deep-hole drilling oil or emulsion (min. 10 – 12% concentration, with additives), is provided in sufficient quantity and pressure.