“…Cutting parameters were selected according to author's previous experience, published papers from other authors and fabricant recommendations [6,9,12]. As it has been already demonstrated the major importance of feed rate when compared with spindle speed in thrust forces development [12], cutting speed was always equal to 53 m/min, corresponding to a spindle speed of 2800 rpm and feed rate had three levels -low, medium and high -table 1. After drilling, hole wall roughness was measured with a Hommelwerke profilometer, with a total travelled length of 1,5 mm, a cut-off length of 0,25 mm, an evaluation length of 1,25 mm, a sampling length of 0,25 mm and a travel speed of 0,15 mm/s.…”