Spark-assisted chemical engraving (SACE) is a flexible, simple and inexpensive method for machining electrically non-conductive materials. SACE is particularly interesting because of the high drilling speed that can be achieved compared to other micromachining technologies. In this paper, the issue of drilling speed decreasing from 100 mu m s(-1) to 10 mu m s(-1) for micro-hole depths more than 200-300 mu m is analyzed. To understand better the material removal mechanism, with the target to eliminate this limit, a model for the material removal mechanism as a hybrid mechanism combining local heating and chemical etching is presented and compared with experimental data. The comparison between the model and experiment allowed the estimation of the machining temperature to be around 600 degrees C.