# Measuring Procedures for Evaluating the Surface Roughness of Machined Parts
## Appendix A  
Surface Roughness Assessment Methodology According to the Standards and Used Methods of Measurement and Data Processing  
Every technology used in the realization of technical surfaces leaves inequalities that are of fundamental importance in the function of these surfaces. It is very difficult to assess the irregularities on the surface, which represent a certain spatial formation. This problem of assessing irregularities (surface structure) is solved by reducing the plane of the section to a plane perpendicular to the surface of the part (Figure 11). The profile of the surface of the component, which is obtained in the plane of the section, is the basic source of information for assessing the structure of the surface of the component. Surface texture--geometrical irregularities contained in a scale-limited profile, or the basic surface profile, is divided into two components according to the spacing of the respective irregularities, namely the component with the smallest spacing forming the surface roughness profile and the component with the largest spacing of irregularities determined by the basic profile, namely the waviness profile. The basic profile is the complete profile before the application of the short-wave filter \(\lambda\epsilon\) (the filter defining the interface between roughness and waviness present on the examined surface). The basic profile represents the basis for the digital processing of the profile using profile filters and for the calculation of profile parameters (Figure 12). Waviness profile--as a profile derived by sequentially applying filters (a filter defining the interface between waviness and longer wave components present on the surface) and profile filters to the base profile (ISO 4287:1997, ISO 4288:1996) [33; 34]. The cut-off system is created to filter the influence of surface waviness on the process of evaluating surface roughness values (Figure A3). The evaluated profile length \(\ln\) is divided into several basic lengths (e.g., 5), and these are evaluated separately. The cut-off system is specified by two parameters (Figure 4):  
* Cut-off \(\lambda c\) (also referred to as \(Lc\) in the text), a profile filter that defines the intersection between roughness and even shorter wave components on the surface. We also call it the shortest cut-off. * Cut-off \(\lambda s\) (also referred to as \(Ls\) in the text), a profile filter that defines the intersection between roughness and waviness of the profile of the surface under consideration. We also call it the longest cut-off. Filtering consists of evaluating the wavelengths between these two limits in order to correctly determine the roughness values of the surface under consideration. Some devices for measuring surface roughness do not allow setting the \(Ls\) value for some evaluation standards. This can have an impact on the \(Ra\) evaluation results, which was also shown when assessing the impact of evaluation standards on \(Ra\) values (see the previous subsection). For filtering the waviness and shape of the surface of the component, it is necessary to select the values of the profile filters of the wavelength \(\lambda c\), \(\lambda s\), and \(\lambda f\) (Figure A4), so that this filtering is possible. After applying profile filters for waviness and shape, it is possible to separate the course of surface roughness, course of waviness, and course of surface shape from the obtained surface profile (Figure A5). For standard surface profile measurements, the surface roughness is filtered into two parts, namely the surface roughness profile and the waviness profile, with the shape of the surface of the part. The newer standard ISO 21920-1 [37] defines these filters with newer designations--profile **S-filter type and profile L-filter type for R-parameter or profile S-filter type for W-parameter**. The indication of the profile L-filter nesting is a value to specify the large-scale lateral components which are removed for the R-parameter.