Gravity-feed drilling is the most commonly used method for micro-hole drilling in glass with spark assisted chemical engraving (SACE). This paper proposes a method allowing the systematic characterization of this drilling method. The influences of voltage, tool shape and force are investigated. It is found that SACE gravity-feed drilling shows two regimes depending on the drilling depth. During the first 200–300 μm, the discharge regime, controlled by the number of discharges inside the gas film, allows fast drilling (up to about 100 μm s–1). For deeper depths, the drilling is controlled by the hydrodynamic regime in which the drilling speed is limited by the flow of the electrolyte inside the micro-hole resulting in slow drilling of typically 10 μm s–1. Furthermore, it is shown how the gas film build-up time is limiting the drilling speed.