## 4 Concluding Remarks  
The cutting tool inserts made out of cubic boron nitride (CBN) with different geometries were examined in terms of the resulting surface integrity of the machined surface of a thin-walled bearing ring. Three insert types were used in the experiments: CNGA120408701030 AWH class 7015 with WIPER geometry, STANDARD insert CNGA120 408501030A with corner radius \(R_{E}\) = 0.8 mm, and insert CNGX1204L025-18 AXA class 7015 with XCEL geometry. In terms of surface integrity, some obtained results can indicate the feasibility of the selected cutting tools for this particular task, as follows. The smallest profile roughness parameters \(Ra\) and \(Rz\) values were obtained for the samples machined with XCEL cutting tools. However, none of the examined inserts and applied machining parameters ensured the fulfillment of the prescribed tolerance condition of \(Rz\) = 1.6 \(\upmu\)m. From the results of the \(Rmr1\), a different trend can be seen. The rings P1 and S2 (WIPER and XCEL) had the smallest material share of the peak, while the rings Q2 and S1 (again, WIPER and XCEL, but with different cutting conditions) had the largest material share. All tested inserts ensured an acceptable limit rate according to the document, \(Rmr1\geq 10\%\). On the other hand, among 3D parameters, the largest \(Sa\) values were obtained for bearing rings machined with STANDARD tools, while the smallest \(Sa\) were obtained  
Figure 12: Results of shear stress \(\tau\) measurement. with XCEL tools. Similarly, STANDARD tool inserts provided the largest values for the parameter \(Sz\), and the smallest values of \(Sz\) were again obtained with STANDARD tools, but at different cutting conditions. Moreover, the smallest \(Sz\) values were those obtained with XCEL inserts. Notably, WIPER inserts provided the largest dispersion of the spatial topography parameters. In turn, the largest values of \(Smr1\) appeared for thin-walled bearing rings machined with WIPER and STANDARD cutting tools, which suggested lower service life and rapid wear of the rings machined with XCEL tools. Another component of the surface integrity, residual stress in the upper layer, indicated that all examined inserts provided a certain surface hardening of the rings. Hence, it is possible to assume a sufficient service life of the part. The highest compressive normal residual stresses were identified in the surfaces layers of the rings machined with XCEL cutting tools. The stress value variations in the individual rings were around 10%, while their absolute values ranged from 500 to 850 MPa. Additionally, shear stresses were also identified since they corresponded with the displacement of individual microstructural layers inside the material, indicating an imperfect cutting process or excessive stretching of the material. In general, their absolute values did not exceed 40 MPa. Due to the low values compared with the yield strength \(R_{e}=590\) MPa, their effect on the functionality and durability of the bearing rings can be considered negligible. Thus, it can be stated that STANDARD cutting inserts were able to ensure both the largest and the lowest \(Sa\) and \(Sz\) values, dependent on cutting conditions. The largest, rather favorable value of \(Smr1\) was a result of work with STANDARD cutting tools, too. The rings machined with WIPER tools had one of the smallest material shares of the peak \(Rmr1=23\%\), while at different cutting conditions the material share could reach \(Rmr1=31\%\). Large values of \(Smr1=27\%\) were achieved after machining with WIPER. XCEL cutting inserts ensured the smallest profile parameters \(Ra\) and \(Rz\), but \(Rmr1\) appeared to be the smallest for the larger feed value \(f=0.35\) mm, while the reduced feed of \(0.25\) mm provided one of the highest values of \(Rmr1=31\%\). Similarly, spatial parameters \(Sa\) were the smallest for XCEL tools, but the values of \(Smr1\) appeared to be the smallest. At this stage of the investigation it can be stated that most of the parameters are favorable after XCEL machining.