Context <p>Nanoscale machining of aluminium (Al) has gained considerable attention in precision-manufacturing industries like defence, aerospace, and optics, where high surface quality and dimensional accuracy are of critical importance. The present study adopts molecular dynamics (MD) simulation to perform nanoscale machining of single-crystal Al with a diamond tool. This paper offers a comparative MD analysis of dislocation structures and subsurface damage in Al nanocutting for fresh vs worn tool edges with explicit DXA-based characterisation. The study investigates the impact of the tool geometry on different mechanisms like material removal, dislocation flow, forces, and stress distribution in nanoscale machining. Results show that a sharp tool contributes to easy chip formation with less deformation of the FCC cubic crystal structure of Al, owing to lower cutting forces (~ 15 nN) and a smoother surface. However, a radiused tool causes higher normal forces (~ 50 nN), leading to more subsurface deformation, increased dislocations and structural transformation.</p> Methods <p>Large-scale atomic/molecular massively parallel simulator (LAMMPS) was employed for carrying out the simulation for nanoscale machining, and open visualization tool (OVITO) was used for post-processing and visualisation. The atomic interactions between tool and workpiece were modelled by using interatomic potential models like Tersoff, Morse, and embedded atom method (EAM). In OVITO, common neighbour analysis (CNA) was carried out to characterise the local structural transformations in the MD system. Dislocation extraction algorithm (DXA) was implemented to analyse the dislocation formation and propagation.</p>