Effect of tool flank face geometry on cutting forces and surface integrity in boring of lead-free CW724R brass alloy: Experimental and finite element analysis

Precision boring of lead-free CuZn21Si3P (CW724R) brass alloy is challenged by high shear resistance and poor chip-breaking behaviour. This study examines the thermo-mechanical response associated with cylindrical and radial flank geometries over varying insert widths ( H ) and cutting speeds ( V c = 100 and 150 m/min). Experiments were combined with a quasi-static finite element method (FEM) framework to evaluate force response, stability and surface integrity. The results show that, although higher cutting speeds reduce thrust force through thermal softening, process stability is strongly influenced by flank-workpiece contact conditions. The FEM model predicts forces with errors below 5% in the stable regime ( H < 0.6 mm), whereas the discrepancy increases to 31–34% at larger insert widths ( H ≥ 0.6 mm), indicating the growing influence of dynamic effects beyond the quasi-static representation. The cylindrical geometry provides better vibration suppression and a sub-micron surface finish ( Ra = 0.15 µm), but its larger contact arc also increases frictional energy dissipation. As a result, higher tensile residual stresses (up to 266 MPa) and a deeper subsurface affected layer (35 µm) are produced. Generally, the results indicate a clear trade-off between improved process stability and increased thermo-mechanical surface loading.