The increasing focus on sustainable manufacturing has brought about interest in the bio-based cutting fluids where the mineral oils are being replaced. In the paper, the rice bran oil (RBO) as a renewable and environmentally harmless lubricant is reinforced with copper (Cu) nanoparticles (NPs) to improve its thermophysical and tribological properties when used in machining processes by using waste materials of rice processing. The reinforcement of 0.5 vol.% of Cu-NPs into base oil enhanced thermal conductivity by 51% and the viscosity by 25.7% as compared to unreinforced oil. The tribological measures showed reduced coefficient of friction by 48.9% at 0.5 vol.% of Cu-NPs as compared to rice bran oil (0 vol.% of Cu-NPs). The obtained RBO-Cu nanofluid demonstrated a high dispersion stability and sustainable lubricating properties during the prolonged use. These results imply that the reinforced RBO cutting fluids using Cu can potentially present a sustainable, high-performance solution to precision machining operations that can be sustainable and have a high process efficiency.