This study aims to determine the optimal cutting parameters in order to achieve minimum surface roughness on free form surfaces. Frequently preferred Al 7075-T6 material was used. Free form surfaces on the material were machined in the CNC milling in order to determine the cutting conditions that provide the best surface roughness. An experiment list was created with the Taguchi L16 experiment design for cutting speed, feed rate, stepover and machining strategies. As a result of these experiments, the average surface roughness (Ra) values were measured. Signal-to-noise (S/N) ratios were determined in the Taguchi design, and the most important effect on the average surface roughness among the four factors was found to be the stepover according to the experimental results. In ANOVA analysis, step over was found the 95% confidence level in Ra value.