## 2 Materials and Methods
When evaluating the surface with a roughness of \(RSm\) between 0.13 mm and 0.40 mm, the filter \(\lambda_{c}=0.8\) mm was used and the evaluation length was set to \(l=4\) mm according to the CSN EN ISO 4288:1999 standard. The measurement was performed in a direction perpendicular to the measured part of the bearing ring, as shown in Figure 2(a). On the entire circumference of the bearing ring, three areas with the dimensions of 4 mm \(\times\) 4 mm were measured in the range of 120\({}^{\circ}\). On each scanned area, 5 paths were measured, as shown in Figure 2(b), where the straight lines were evenly distributed over the surface of scanned area. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Notion** & **Cutting Tool** & \
\begin{tabular}{c} **Cutting Speed** \\ **v\({}_{c}\) (m/min)** \\ \end{tabular} & **Feed \(f\) (mm)** &
\begin{tabular}{c} **Cutting Depth** \\ **\(a_{p}\) (mm)** \\ \end{tabular} \\ \hline O1 & & 180 & 0.28 & 0.3 \\ O2 & & 180 & 0.35 & 0.3 \\ P1 & WIPER & 195 & 0.28 & 0.1 \\ P2 & & 195 & 0.35 & 0.1 \\ \hline Q1 & & 180 & 0.15 & 0.2 \\ Q2 & STANDARD & 180 & 0.20 & 0.2 \\ R1 & & 195 & 0.15 & 0.4 \\ R2 & & 195 & 0.20 & 0.4 \\ \hline S1 & XCEL & 195 & 0.25 & 0.25 \\ S2 & XCEL & 195 & 0.35 & 0.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Machining parameters used in the experiments for the respective samples. Figure 2: Insert CNGA120408T01030 AWH class 7015 with WIPER geometry: **(a)** photo from microscope; (**b)** explanation of WIPER geometry. Among the profile parameters, _Ra_ (mean arithmetic deviation of the profile), _Rz_ (the largest height of the profile), and _Rnr(c)_ (material proportion of the profile) were considered. _Ra_ is the most frequently used roughness parameter, but it is not sensitive to the height fluctuations of the evaluated surface profile. Therefore, the _Rz_ parameter was also monitored, especially as it was required by the bearing technical documentation. Additionally, _Rmr1_ was required by the documents to be checked. _Rmr1_ is the material proportion of the profile (supporting proportion), defined as the material ratio of the protrusions (vertices) to the core of the material surface. The material proportion of the profile is typical for individual finishing methods, and its value is especially important for the assessment of loaded functional surfaces, such as friction, lubrication, and wear. Traditionally, the evaluation of surface quality using profile (2D) parameters is common in engineering practice, but nowadays, 3D surface analysis is available and can to provide crucial information on surface integrity. To perform the area measurement of the surface texture, three measured areas 4 mm \(\times\) 4 mm were scanned and distanced by 120\({}^{\circ}\), as shown in Figure 4. From the measured areas with dimensions of 2 mm \(\times\) 2 mm, the height parameters of the surface texture were selected according to the standard CSN EN ISO 25 178-2. Following the standard CSN EN ISO 25 178-3, a Gaussian filter of 0.8 mm was used for the calculation of spatial parameters. Figure 4: Measurement of the surface topography parameters: (**a**) scanned area on the bearing surface; (**b**) example of the screen during measurement, where red lines divide the scanned area into four analyzed sections. Figure 3: Measurement of the profile parameters: (**a**) scanned area on the bearing surface; (**b**) example of the screen during profile measurement, where red lines correspond with analyzed profiles on the scanned area. In the analysis, the following parameters were considered: _Sa_ (mean arithmetic height of the limited scale of the surface), _Sz_ (maximum height of the limited scale of the surface), and _Smr1_ (material proportion of the surface), which somehow corresponded with the 2D parameters listed above. The parameter _Sa_ is the most frequently used one; it represents spatial characteristics that correspond to the roughness profile parameter _Ra_.