# Measuring Procedures for Evaluating the Surface Roughness of Machined Parts
## Appendix C Periodic Surface Roughness Profiles-Experiments  
For milling with a slab mill cutter (Milling operation with slab mill cutter), a selected sample, measured at the same place but with different values of the cut-off filter \(Lc\), is shown (Figure 16). It can be seen from the given graphic curves that for the cut-off filter \(Lc\) with the smallest value, its value is too small and therefore does not capture the actual value of the quantity Ra after evaluation. At other values, the periodic pattern characteristic of this technology is already visible. The effect of waviness is only slightly visible at the largest used value of the cut-off filter \(Lc\) = 2.5 mm. For milling with a cylindrical cutter (Milling operation with slab mill cutter), samples with nominal values \(Ra\) = 1.52 \(\upmu\)m were experimentally examined; 3.57 \(\upmu\)m; 6.05 \(\upmu\)m; 10.25 \(\upmu\)m; 16.25 \(\upmu\)m. The \(RSm\) values for all these samples measured at different settings of the cut-off filter \(Lc\) are shown in Figure 17, and it follows from them that the only suitably chosen value of the cut-off filter \(Lc\) is 2.5 mm. At the other values of the cut-off filter \(Lc\), the values of \(RSm\) were outside the range of the instrument or could not be evaluated. The \(Ra\) values for milling with a slab mill cutter (Milling operation with slab mill cutter) were determined for different values of the cut-off filter \(Lc\) and are in accordance with ISO recommendations (Figure 18). For milling operation with a face mill cutter, a selected sample with a nominal value of \(Ra\) = 3.46 \(\upmu\)m measured at the same place but with different values of the cut-off filter \(Lc\) is shown. From the contours of the surface roughness profile of the sample, it can be seen that the first two contours have a poorly chosen cut-off filter \(Lc\) and the contours do not capture a representative sample of the course characteristic of this type of technology. The other two surface roughness profile records already provide a surface roughness profile that can already be analyzed. In the last surface roughness profile, a slight influence of the waviness of the surface profile is already visible (Figure 19). Figure A16: Surface roughness profile measured using different settings of the cut-off filter \(Lc\) for milling with a slab mill cutter (Milling operation with slab mill cutter) for a sample with a nominal value of \(Ra=3.57\) μm. For milling operation with a face mill cutter, samples with nominal values \(Ra=1.71\)\(\upmu\)m 3.46 \(\upmu\)m; 6.17 \(\upmu\)m; 11 \(\upmu\)m; 19.25 \(\upmu\)m were experimentally examined. The \(RSm\) values for all these samples determined at different settings of the cut-off filter \(Lc\) are shown in Figure A20, and from them, it follows that for samples \(Ra=1.71\)\(\upmu\)m; 3.46 \(\upmu\)m, \(RSm\) valuesare similar at \(Lc\) = 0.8 mm and at \(Lc\) = 0.25 mm. For other samples, the only appropriately chosen cut-off value of the \(Lc\) filter is 2.5 mm, and at other cut-off values of the \(Lc\) filter, the \(RSm\) values were very low or could not be evaluated (Figure A20). The Ra values for face milling were determined for different values of the cut-off filter \(Lc\) and are in accordance with ISO recommendations (Figure A21). For the 19.25 \(\upmu\)m sample, the recommended filter cut-off value is \(Lc\) = 8 mm, which is not shown on the graph because the used surface tester does not have this setting available (Figure A21). For turning, a sample with a nominal value of \(Ra\) = 2.78 \(\upmu\)m is shown (Figure A22). With the first two values of the cut-off filter \(Lc\), it is again visible that the sample does not correspond to the nature of the turning technology, and the cut-off filter parameter \(Lc\) is poorly chosen. In the case of a sample with a filter cut-off parameter \(Lc\) = 0.8 mm,the course of the surface roughness profile already corresponds to the technology of this sample, and the filter cut-off parameter \(Lc\) is appropriately chosen.