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The aim of this study is to investigate the effects of drilling parameters such as friction angle, friction contact area ratio (FCAR), feed rate and spindle speed on workpiece surface temperature, thrust force and torque in friction drilling of ST12 material. The tool material is tungsten carbide coated with TiN treatment. Experimental results reveal that the thrust force and torque increases gradually with increasing friction angle, feed rate and FCAR. On the other hand, the thrust force and torque decreases with increasing drilling speed. It is found that drilling speed has an important effect on the workpiece surface temperature. As the drilling speed increases, the workpiece surface temperature increases. Increasing or decreasing the friction angle and FCAR has no significant effect on the workpiece surface temperature.

In this study, effects of cutting speed (V), feed rate (f), depth of cut (a) and tool tip radius (R) on  surface roughness (Ra, Rz, and Rt) and cutting forces (radial force (Fx), tangential force (Fy), and feed force (Fz)) in hard finish turning processes of hardened 42CrMo4 (52 HRC) material was investigated experimentally. Taguchi’s mixed level parameter design (L18) is used for the experimental design (2x1,3x3). The signal-to-noise ratio (S/N) was used in the evaluation of test results.  By using Taguchi method, cutting parameters giving optimum surface roughness and cutting forces were determined. Regression analyses are applied to predict surface roughness and cutting forces. Analysis of variance (ANOVA) is used to determine the effects of the machining parameters on surface roughness and cutting forces. According to ANOVA analysis, the most important cutting parameters were found to be feed rate for surface roughness and depth of cut among cutting forces.  By conducting validation experiments, optimization was seen to be applied successfully.