For the most part, today's manufacturing companies aim to produce high-quality goods at an affordable price in the shortest length of time. The appropriate cutting parameters for each operation must be determined in order to increase machining quality and reduce machining expenses. Hard turning is increasingly being utilized as an alternate to grinding in the finishing of hardened steel work pieces because of its high productivity, flexibility, and ability to avoid the use of coolants. It is the goal of this study to discover the best parameters for CNC hard turning of C45. When designing an experiment, the Taguchi's L9 Orthogonal array is utilized to determine how different parameters affect machining characteristics and to anticipate the best settings for various turning factors like Spindle speed, depth of cut (DOC) and Feed rate. At 1200 rpm, 0.1 mm/rev Feed rate in addition a 0.3 mm DOC, the best surface roughness was attained. The percentage of contribution for surface finish majorly influenced with speed 63 %. © 2025 Elsevier B.V., All rights reserved.