The objective of this paper is to understand the abrasive wear mechanism for producing a nano scale groove on a bulk material through nano machining. A nano indenter equipped with a nano scratching attachment was used for nano machining operation and in situ observation of the machined surfaces. Two different tools (Berkovich and Conical) with the same tip radius (100nm) but different edge geometries were used to machine both Copper and Nickel coatings. It was found that the percentage of elastic recovery was lower for Cu than Ni during this nano machining operations. Hence, the deformation mechanism in nano machining operation was identified as elasto-plastic in nature as opposed to the well established completely plastic mode of conventional machining operations. The pile up volume due to plastic deformation was utilized to distinguish between the ploughing and cutting modes of abrasive wear mechanisms. The results reveal that the ploughing mechanism was dominant for Cu and the cutting mechanism was dominant for Ni machining. Moreover, both mechanisms ploughing and cutting were the dominant modes of abrasive wear using the Berkovich tip compared to the Conical tip for producing a nano scale groove through nano machining.