AIM: The main aim of the research is to compare Machinability performance of Novel Titanium Silicon Nitride coated High speed steel tool with Un-coated High speed steel tool for CNC green machining of unalloyed medium carbon steel (EN8) for improving machining rate and surface finish. Materials and Methods: EN8 steel rod of diameter 20 mm and length 50 mm was used in this research work. EN8 steel was normalized at 650 degree Celsius and annealed at 840 degree Celsius with the help Quenching in oil or water after heating to this temperature will harden the steel. Test samples per group (N = 16+16=32) where CNC turning operation is used to find the surface finish taken from each rod of experimental group and control group (unalloyed EN8 steel). Total sample size used for the Groups is 32 and 80% of G power is calculated using the software G Power 3.1. Results: Within this limitations of study the confidence level of cutting parameters and the response Surface Roughness values are obtained for all machined specimens with both HSS tool and Novel Titanium Silicon Nitride coated High speed steel tool and the results done by Turning were conducted with speed, feed and depth cuts to turning process with an MRR is 350mm3/min and depth of cut affects considerably cutting force and power (62.31% and 60.72%). And the Surface Roughness is 19.04%. Using TiSiN coated HSS tool gives lower surface roughness than HSS tool in Computerized Numerical Control machining.Then the observation shows that it is actually because the T test output significant value are: P= 0.027 for MRR and P=0.010 for SR and they are P< 0.05. Conclusion: Within the limitations of the studies, the optimization of EN8 carbon steel Material removal rate, Surface finish and Surface Roughness using response of Novel Titanium Silicon Nitride. The results obtained revealed that spindle speed,feed rate and depth of cut have a significant influence on the MRR was also absorbed that optimum machining setting of spindle at 500 rpm, the feed rate of 0.4mm/rev and depth is 0.2mm resulted in a turning process with an MRR.