<p>Within the scope of sustainable production, a natural liquid mixture that will act as cutting fluid issprayed with a different system. The liquid consisting of water and soybean oil was pulverized byultrasonic atomization method and used by spraying with 4 bar compressed air. In this study, it wasaimed to investigate the effects of AISI 4140 steel on machinability in CNC lathe by using uncoatedcarbide insert (SECO WNMG080404-M1). Three cutting speeds (150, 200, 250 m / min), three feedrates (0.1, 0.15, 0.2 mm / rev) with four cutting fluids (1%, 5%, 10% soy oil-water mixture andcommercial cutting fluid) and the comparison was made by making experiments under dry cuttingconditions. In all experiments, the cutting depth was 1 mm and the cutting length was 100 mm. As aresult of the experiments, cutting force, surface roughness and tool wear values were examined andcontact angle measurements of cutting fluids were made. The best results in all parameters wereachieved by spraying a 10% soybean oil-water mixture using an ultrasonic atomizer. The best results inall parameters were achieved by spraying a 10% soybean oil-water mixture using an ultrasonic atomizer.The worst values occurred in experiments conducted under dry cutting condition. In addition, SEMphotographs were taken to observe the type of tool wear.The obtained values were analyzed with the ANOVA method and the results were evaluated with 3Dsurface graphics. After evaluating the analysis results, percentage impact rates, regression analysisequations and optimization values are proposed.<br></p>