## 3 Results and Discussion
An exception was made in the situations in which the cutter encountered radial surfaces and this caused detachment of some ray tissues, as can be seen in Figure 13b, which significantly increased Rv (Figure 14), with approximately 40%, for the feed speed  
Figure 12: Images of beech milled profiles (**a,b**) and microscopic details (**c,d**) at magnification 22.5\(\times\). (**a,c**) Processing by n\({}_{1}-\)v\({}_{\text{f1}}\); (**b,d**) processing by n\({}_{1}-\)v\({}_{\text{f2}}\). Examples of raised fibers are marked with blue ellipses. \(\
u_{\rm f2}\) in comparison with \(\
u_{\rm f1}\) (Table 4, Figure 14). Wood pores went beyond the marks left by the tool on the wood, and this is observed by a negative Rsk and a subunitary ratio Rpk/Rvk. The same is true for the ratio A1/A2, which indicates a larger share of the area of the valleys compared to the area of the peaks (Table 4). An increase in the rotation speed from n1 to n2 has significantly reduced Rv (Figure 14) with approximately 33% for the feed speed \(\
u_{\rm f1}\) (ANOVA and Dunnett T3). Interpretation of surface quality in the case of wood is complex. For optimization of the cutting quality and selection of the best working parameters, the tool marks are of interest. From this perspective, Rk parameter is representative and has shown it is significantly influenced by the feed speed and was less affected by the selection of the rotation speed. The surface fuzziness and accidental material detachment will be species-dependent and of wood local anatomy. However, their effect on the overall surface quality cannot be neglected. A statistical analysis ANOVA followed by Dunnett T3 test performed on the cumulative effect of processing plus the raised fiber (Rk+Rpk) has led to the same  
Figure 14: The variation of the deepest valley, Rv, with combinations of the rotation speed with the feed speed. With blue arrows, pair means that differ statistically are marked. Figure 13: Samples processed by milling with \(n_{2}\) rotation speed. (**a**) Feed speed \(\
u_{\rm f1}\); (**b**) feed speed \(\
u_{\rm f2}\). The red rectangle exemplifies a radially cut surface which contains detached ray tissues. conclusions as in the case of Rk alone: the feed speed was the most important factor affecting the surface quality by milling. Although the surface quality has improved by increasing the rotation speed, its effect was not significant (Tables 9 and 10). The best surface quality was obtained when combining n\({}_{2}\) (6594 rot/min) with v\({}_{\text{f1}}\) (6.53 m/min) and the worst when the rotation speed n\({}_{1}\) (3308 rot/min) was combined with the high feed speed v\({}_{\text{f2}}\) (23.74 m/min), as shown in Figure 15.  
When the surface isolated gaps were included, together with the tool marks and the raised fiber, not only the feed speed was a significant factor, but also the rotation speed, the surface quality improving for the highest rotation speed n\({}_{2}\) in comparison with n\({}_{1}\) (Figure 16, Tables 11 and 12). Another test was conducted to monitor the surface quality  
From the profiles presented in Figure 17, it can be observed that after using the tool by continuous processing for 600 m cutting distance, the surface quality improved (Figure 18). The surface improvement was also sensed by touch, but it is visible also in Figure 18c,d taken as example. A statistical comparison of the composed parameter Rk+Rpk+Rvk was performed in order to obtain a global evaluation of the surface improvement. The ANOVA test followed by a Post Hoc test Games-Howell (groups had unequal number of measurements) indicated a surface improvement after the tool was working 600 m, which was significant when the high feed speed was used (v\({}_{\mathrm{f2}}\) = 23.74 m/min). The improvement was quantified to 30% roughness decrease for the rotation speed n\({}_{2}\) and to 34% when the rotation speed n1 was used.