## 3 Results and Discussion
### Profile and Topography Measurement Results  
Figure 7 presents a comparison of the profile parameters \(Ra\) obtained for different samples. Since the measurement was repeated for each sample, the average results are shown. In the diagram, 3D parameter \(Sa\) is presented, too. In general, there was no significant difference between 2D and 3D results, because the \(Sa\) parameter does not distinguish between peaks and valleys. In most of the bearing rings, the dispersion of the results was quite similar. A significant difference was seen in bearing ring O1, where 3D parameter \(Sa\) exhibited the largest dispersion of ca. 0.2 \(\upmu\)m. This difference was due to the measurement of a larger area where some unevenness was noted, unnoticed by the profile measurement. These local deviations could have appeared either through mishandling of the sample or a manufacturing error. From the graph in Figure 7, it can be noted that the largest value \(Ra\) appeared in the rings Q2 (\(Ra\) = 1.429 \(\upmu\)m) and R1 (\(Ra\) = 1.333 \(\upmu\)m). Both samples were machined with  
Figure 6: Example of a screen with the results of residual stress measurement. Figure 7: Average results of profile roughness \(\overline{Ra}\) and respective 3D parameter \(\overline{Sa}\) measurement of the examined samples. the cutting tool denoted STANDARD. In contrast, the smallest measured \(Ra\) values were obtained for rings S1 (\(Ra\) = 0.494 \(\upmu\)m) and S2 (\(Ra\) = 0.496 \(\upmu\)m). These samples were machined with the XCEL tool. In these cases, STANDARD cutting inserts produced surfaces with three times higher roughness \(Ra\) than those machined by XCEL inserts. The results of roughness measurement \(Rz\) and respective topography \(Sz\) are shown in Figure 8. The overall trend of \(Rz\) is similar to the one exhibited by \(Ra\); namely, the highest values were obtained for Q2 and R1 samples, while the lowest were obtained for S1 and S2 (\(Rz\) = 2.375 and 2.308 \(\upmu\)m, respectively). Hence, the XCEL geometry of CBN cutting inserts contributed to the best roughness of the machined surface. However, even these lowest values did not fit the tolerance specified in the technical documentation, \(Rz\) = 1.6 \(\upmu\)m. This result can be evaluated as indicating a poor state of surface integrity, which isunfavorable for the functionality of the component and its durability. From the graph in Figure 8, it is seen that the largest values for the surface parameter \(Sz\) were obtained for bearing rings Q2 (\(Sz\) = 9.217 \(\upmu\)m) and R1 (\(Sz\) = 7.657 \(\upmu\)m) machined with the STANDARD tool. Considering the especially large dispersion of the results \(\pm\)2 \(\upmu\)m for the Q2 sample, greater wear of this component can be expected. On the other hand, the smallest surface parameters \(Sz\) were measured for bearing rings S2 (\(Sz\) = 5.499 \(\upmu\)m) and S1 (\(Sz\) = 5.499 \(\upmu\)m) machined with the XCEL tool, but also for O1 (\(Sz\) = 5.731\(\upmu\)m) machined with the WIPER tool and R2 (\(Sz\) = 5.885) for the STANDARD tool. Considering the requirements related to the thin-walled bearing rings, it can be assumed that the surface integrity of these four samples significantly reduced the risk of a crack forming, and thus increased the service life of the bearing. Notably, two out of four of the samples that exhibited a low \(Sz\) parameter were fabricated using the cutting inserts of XCEL geometry. It should be noted, however, that the \(Sz\) results for both samples S1 and S2 showed very high dispersion. Specifically, the S1 ring exhibited a dispersion of \(\pm\)4 \(\upmu\)m, which indicated low repeatability of the appearance of the highest peaks and the deepest depressions throughout the surface of the ring. A representation of the material proportion of the profile \(Rmr1\) and surface \(Smr1\) is presented in the diagram in Figure 9.  
Some different trends can be seen than those for the previous parameters \(Ra\) and \(Rz\).