The research aims at investigation of surface roughness technological assurance in slot milling using various toolpath strategies. Surface roughness is one of the main quality assurance parameters and essential for surfaces that interact with each other during exploitation of any mechanism. In this study technological assurance was investigated on carbon steel material (C45) which has found wide use in mechanical engineering. Technological assurance involves adjustment of slot milling strategy and cutting parameters. Milling strategy involves a choose between different toolpaths: one-way slotting, two-way slotting and adaptive/trochoidal cutting. Cutting parameters to be adjusted are cutting speed, feed rate and depth of cut. Experiments were conducted on 3-axis CNC machine. The relation between the toolpaths, cutting parameters and surface roughness were analysed. From experimental results, it was concluded that the best surface roughness was obtained under increased cutting speed and low feed. This research identifies that the cutting parameters influence surface roughness and better surface roughness can be obtained at the proper cutting conditions. This study focuses on quality assurance and machine tool dynamics.