Influence of Some Cutting Parameters on Frontal-Peripheral Surface Roughness of Oak Milled with Straight-Flute End Mill Tools

Abstract

The combined effects of grain orientation and CNC end milling parameters on wood surface quality remain poorly understood. This study investigated the surface quality of tangential oak during frontal milling and radial oak during peripheral milling using straight-flute end mill tools with diameters of 8 and 10 mm, four stepover values (30%, 50%, 70%, and 90% of the tool diameter), and two cutting depths (1 and 3 mm). Surface quality was evaluated through roughness parameters and profiles, microscopic observations, and compared with reference surfaces obtained by shaving and P150 sanding. ANOVA revealed that stepover is the primary factor governing roughness, followed by tool diameter, while cutting depth had no statistically significant impact. Increasing the stepover beyond 50% substantially degrades the surface due to severe fiber lifting and tool ridges. The 8 mm tool produced smoother surfaces than 10 mm tool, in both milling operations and at 30% stepover closely approached the ideal shaved baseline. In frontal milling, stepovers of 30% and 50% outperformed sanding, whereas in peripheral milling, only the 8 mm tool yielded superior quality. Utilizing a smaller tool diameter at a low stepover ratio guarantees a finish-ready surface directly from the CNC machine.