## 2 Surface Machining and Roughness Measurement  
Our research focuses on the analysis of surface roughness generated by diamond burnishing. To ensure consistency, standardized test specimens were manufactured using machine tools located in the workshop of the Institute of Manufacturing Science at the University of Miskolc. The geometric dimensions of the specimen used for the burnishing experiments were six adjacent cylindrical surfaces with a diameter of \(\mathcal{O}\)50.00 mm and a length of 22 mm. The chamfers, grooves, and clamping positions are formed by turning X5 CRNI18-10 austenitic stainless chrome-nickel steel alloy with austenitic fabric construction with a yield strength of \(R_{p0.2}\geq 210\) MPa, a tensile strength of \(R_{m}=520-700\) MPa, an elongation at break of \(A\geq 45\%\), a density of \(\rho=7.9\) kg/dm\({}^{3}\), and a hardness of \(160-190\) HB. Chemically, the alloy consists of 66.8-71.3% iron, \(\leq\)0.03% carbon, 1% silicon, 2% manganese, 0.045% phosphorus, 0.015% sulfur, \(\leq\)0.11% nitrogen, 17.5-19.5% chromium, and 8-10.5% nickel. The turning parameters were kept uniform across all specimens:  
\[v_{c}=1.3875\Big{[}\frac{m}{s}\Big{]}\;f=0.05\frac{mm}{rev}\]  
This consistency enabled us not only to evaluate the surface roughness after diamond burnishing but also to assess the degree of roughness improvement--namely, how much surface quality enhancement was achieved compared to the initial turned surface. This comparison is especially relevant since identical turning parameters do not necessarily result in identical surface roughness values. Diamond burnishing was also performed on a lathe (type: EU-400-01), where the burnishing tool was mounted in the tool post. The machining setup is shown in Figure 2, in which the following are classified: 1: workpiece; 2: burnishing tool body; 3: burnishing  
Figure 1: Structure of this paper. insert; 4: tool holder; 5: diamond tip. The spring mechanism is also visible, through which the burnishing force can be indirectly controlled by adjusting the spring tension. The technological parameters of diamond burnishing were combined using two feed rates, two spindle speeds, and four burnishing forces. The independent parameter combinations are given in Table 1. The experimental parameter variations are written as follows:  
Feed rate:  
\[f_{1}=0.05\frac{mm}{rev};\ f_{2}=0.1\frac{mm}{rev}\]  
Workpiece RPM:  
\[n_{1}=265\frac{1}{min};\ n_{2}=375\frac{1}{min}\]  
Burnishing force:  
\[F_{\rm p1}=60\ N;\ F_{\rm p2}=80\ N;\ F_{\rm p3}=100\ N;\ F_{\rm p4}=120\ N\] \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & \(f[\frac{mm}{rev}]\) & \(n[\frac{1}{min}]\) & \(F_{\rm p}[N]\) \\ \hline
1-1 & 0.05 & 265 & 120 \\
1-2 & 0.05 & 265 & 100 \\
1-3 & 0.05 & 265 & 80 \\
1-4 & 0.05 & 265 & 60 \\
2-1 & 0.1 & 265 & 120 \\
2-2 & 0.1 & 265 & 100 \\
2-3 & 0.1 & 265 & 80 \\
2-4 & 0.1 & 265 & 60 \\
3-1 & 0.05 & 375 & 120 \\
3-2 & 0.05 & 375 & 100 \\
3-3 & 0.05 & 375 & 80 \\
3-4 & 0.05 & 375 & 60 \\
4-1 & 0.1 & 375 & 120 \\
4-2 & 0.1 & 375 & 100 \\
4-3 & 0.1 & 375 & 80 \\
4-4 & 0.1 & 375 & 60 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Data of the diamond burnishing parameter variations. Figure 2: Schematic representation of the diamond burnishing process [72]. Using the relationship of frictional forces, Equations (3) and (4) can be written. Equation (3) uses traditional notation, while Equation (4) applies our chosen symbols, written as follows:  
\[F_{s}=\mu\cdot F_{\mu},\ [\text{N}\cdot] \tag{3}\]  
\[F=\mu\cdot F_{\
u},\ [\text{N}\cdot] \tag{4}\]  
Here, \(\mu\) is the coefficient of friction, which is taken as \(\mu=0.1\) for the diamond-steel interface with coolant/lubricant applied [73]. In our study, we analyzed surface roughness using various metrics, including both 2D [8] and 3D roughness parameters. Measurements were conducted using the AltiSurf 520 roughness measurement system, and data analysis was carried out using the AltiMap software provided with the equipment. Technical specifications of AltiSurf\(\oplus\)520 can be found in [74].