# Measuring Procedures for Evaluating the Surface Roughness of Machined Parts
## Appendix A
The indication of the profile S-filter nesting index is a value to specify the small-scale lateral components which are removed for P- and W-parameter (ISO 21920-2) [38]. Profile S-filter is a profile filter that removes small lateral scale components from a profile. Profile L-filter is a profile filter that removes large lateral scale components from a profile. The setting of measurement parameters is defined in ISO 21920-1 [37] as Symbol 'Scn' to specify a setting class number**. The symbol Scn indicates what setting class number for the determination of the default settings shall be applied. The setting class number or a default profile L- or S-filter nesting index value shall be specified for the parameter without defined defaults (ISO 21920-3) [39]. **Primary surface profile--**_P_: surface profile trace obtained when a surface profile trace is represented as a specified primary mathematical model with a specified nesting index _Nis_. Primary profile--_p_ profile is scale limited profile at any position \(x\) derived from the primary surface profile by removing the form using a profile F-operation with nesting index _Nif_. The primary profile is the basis for the evaluation of the primary profile parameters. **Waviness profile--**_W_ profile is scale limited profile at any position \(x\); derived from the primary profile by removing small-scale lateral components by a profile S-filter with a specified nesting index _Nic_ and with a specified type of filter. The waviness profile is the basis for the evaluation of the waviness profile parameters. **Roughness profile--**_R_ profile is scale limited profile at any position \(x\) derived from the primary profile by removing large-scale lateral components by a profile L-filter and with the same nesting index _Nic_ and the same type of filter specified for the profile S-filter to obtain the waviness profile. The roughness profile is the basis for the evaluation of the roughness profile parameters. For the evaluated quantities, the following are then distinguished:  
P-prefix parameter--parameter calculated from the primary profile,  
W-prefix parameter--parameter calculated from the waviness profile,  
R-prefix parameter--parameter calculated from the roughness profile. **Evaluation length**_lm_--The indication of the evaluation length (Figure 6) is a value to specify the length used for identifying the geometric structures characterizing the scale-limited profile (ISO 21920-2) [38]. In the former ISO 4287 [33] profile standard, the evaluation length was given by _ln_. Evaluation length is length in the direction of the _x_-axis used for identifying the geometric structures characterizing the scale-limited profile. The evaluated length can contain one or more section lengths. The profile filter is a tool for dividing the profile into long-wave and short-wave components. The filtration process is carried out in several stages, providing modified profiles. **Section length**_lsc_--The indication of the section length is a value to specify the length used to obtain height parameters based on profile peaks and profile valleys (ISO 21920-2) [38]. Section length _lsc_ or _lp_, _lr_, _lw_ is the length in the direction of the x-axis used to recognize the irregularities characterizing the evaluated profile. Section length for the roughness _lr_ and for the waviness profile _lw_ are numerically equal to the characteristic wavelength of the profile filter \(\lambda c\) and \(\lambda f\). Section length for the basic profile \(lp\) is equal to the evaluated length. **Number of sections--**The indication of the number of sections (Figure A6) is a value to specify the number used to obtain height parameters based on profile peaks and profile valleys (ISO 21920-2) [38]. The Number of sections shall be an integer number. STN EN ISO 4287 [33] and ISO 21920-2 [38] expands the possibilities of surface evaluation by the fact that almost all parameters defined in it can be applied to the primary profile, roughness profile, and waviness profile.