In this study, steel AISI 1050 is subjected to process of face milling in CNC milling machine and such parameters as cutting speed. feed rate. cutting tip, depth of cut influencing the surface roughness are investigated experimentally. Four different experiments are conducted by creating different combinations for parameters. In conducted experiments. cutting tools, which are coated by PVD method used in forcing steel and spheroidal graphite cast iron are used. Surface roughness values. which are obtained by using specified parameters with cutting tools, are measured and correlation between measured surface roughness values and parameters is modeled mathematically by using curve fitting algorithm. Mathematical models are evaluated according to coefficients of determination (R-2) and the most ideal one is suggested for theoretical works. Mathematical models. which are proposed for each experiment, are estipulated.