The minimum uncut chip thickness (MUCT) is an important phenomenon observed both in orthogonal and oblique cutting. Rounding the cutting edge influences the initiation of the cutting process and chip formation. In a previous study, the authors presented a theoretical analysis and experimental validation on the effect of edge inclination angle λs in the range of 0° to 60° on hmin in radial-free turning of C45 steel. The current work investigated the MUCT hmin in oblique cutting process of C45 steel, for extremely high value of edge inclination angle λs. In this research, a special technique based on milling tool machine using a special tool and sample is presented. Enabled model tests in the unprecedented range of angles λs not used in research to date. The samples were machined using a cutting speed vc = 0.063 m/min. Vertical feed of edge fv was determined by association on the applied sample slope (τ = 0.60–0.85 mm/m) and cutting speed vc. as fv = 37.8—53.5 μm/min. MUCT hmin parameter was measured using compensation for the effects of deformation, based on profilogram analysis. The machining experiments were carried out using a tool with rn = 185 μm. It was found that in the range of angles of 50° ≤ λs ≤ 85°, the MUCT decreases from hmin = 12 μm for λs = 50° to hmin = 4 μm for λs = 85°. Increasing λs by 35° resulted in up to threefold reduction in MUCT. The analysis of the experimental results of hmin for the range of studied λs angle confirmed authors previously reported theory for extreme values of λs. In optimization procedure based on LSM, chip flow angle coefficient was determined as k = 0.75 and critical value of rake angle γcf = -64.8°. This feature provides prediction of results with great accuracy to experimental value. The findings from this study opens the possibility of developing new tools for finishing operations in the field of oblique cutting with high values of λs angle. In addition, the results introduce new area for research on improving the surface quality based on lowering the effect of MUCT on surface roughness and explaining some aspects related to surface wear in the friction process.