## 3 Results  
### Quality Evaluation of the Shaved Surfaces  
Processing wood surfaces with a super surface provides an exceptionally smooth finish in which the influence of machining roughness is minimal or negligible. As a result, the surface texture primarily reflects the natural anatomical structure of wood and its cellular diversity. A shaved surface, as an almost ideal smooth surface, can be used as a quality reference for any type of processing, that is, CNC milling in this research. The shaved surfaces of maple and oak were very smooth to touch and shiny. As shown in Table 2, the roughness parameter values differed between maple and oak, even though both species were processed under identical conditions. The reason is that those roughness parameters are strongly influenced by the particular species' anatomical cavities. However, the least affected parameter was Rk, whose mean value was similar for both species, despite their anatomical differences. This result indicates once more that Rk is the parameter that best approximates the surface roughness caused by machining, namely, the shaving operation in this case. Figure 4 illustrates an example of the corresponding roughness profiles for both species. The red curve represents the maple profile, and the blue curve corresponds to oak. The irregularities observed below the black horizontal axis (the zero line) represent the lumens of wood cells, particularly the vessel voids, emphasizing that the surface topography was anatomically driven rather than mechanically induced. Although \(y\)-axis values are displayed, each roughness profile was vertically offset and referenced to its own zero line. This approach was adopted to facilitate a more effective comparison between the two species. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Reference Surface** & **Ra** & **Rk** & **Rpk** & **Rvk** & **Rk + Rpk** & **Rv** \\ \hline Maple & 3.83 (0.11) & 6.16 (0.21) & 1.27 (0.09) & 16.21 (0.64) & 7.43 (0.66) & 45.79 (3.19) \\ Oak & 9.96 (1.83) & 6.46 (0.62) & 2.37 (1.44) & 63.36 (10.80) & 8.83 (11.75) & 165.04 (8.98) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean roughness parameters of the reference surfaces processed by super surfacing (shaving) for maple and oak. All roughness values are in \(\mu\)m, and the values in brackets represent the standard deviation. Although Ra is widely used to characterize a surface texture and is an average value of all surface irregularities [2; 16; 28; 29; 30; 31; 32], especially in the case of a very smooth finish combined with deep anatomical voids, it proves to be sensitive to anatomical features rather than to machining effects. Significant statistical differences in Ra were observed between map and oak, despite the controlled and uniform shaving process that eliminated variability due to the cutting conditions. These differences are rooted in the distinct microscopic structures of the two species. Maple exhibits small, diffuse pores uniformly distributed across the growth ring, with diameters of approximately 25-30-50-70 (110) and a vessel proportion of 4-8.4% [33]. Combined with a sparse parenchyma, this leads to a smooth and uniform surface, resulting in a low Ra value (3.83). In contrast, oak is characterized by large, ring-porous vessels in the earlywood, with diameters reaching up to 350-500 and a vessel area proportion that can exceed 40% in narrow growth rings, along with prominent, dense rays [33]. These features create a pronounced surface texture, reflected in a considerably higher Ra (9.96). Therefore, Ra cannot be considered a reliable parameter for assessing surface quality in smoothly processed oak wood, as it predominantly captures anatomical variations rather than the actual effects of machining [1]. For both species, the low Rpk values indicate a surface with minimal protrusions and no prominent peaks, an expected result of the shaving process, which effectively levels the surface, thereby enhancing smoothness and visual uniformity.