A processor implemented method for monitoring tool wear to estimate Remaining Useful Life of a tool, the method comprising: obtaining, by one or more hardware processors, a plurality of process parameters associated with machining process of a work piece, wherein the plurality of process parameters, comprising a spindle power ( S p), a radial depth of cut ( w) of the tool, an axial depth of cut t of the tool, and a cutting velocity V, are obtained directly from a Computer Numerical Control machine; deriving, by the one or more hardware processors, a rate of volumetric wear loss per unit contact area of the tool in terms of a rate of change of flank wear width ( dVB dt) of the tool, wherein the rate of change of flank wear width ( dVB dt) is computed using the spindle power ( S p), the radial depth of cut ( w), the axial depth of cut t of the tool, the cutting velocity V, predetermined constants A 1 and B 1 defined in accordance with a combination of the tool and material of the work piece, and a predetermined temperature wear coefficient ( K w), wherein the temperature wear coefficient K w considers effect of temperature rise due to friction caused by a current tool wear state of the tool during the machining operation; determining, by the one or more hardware processors, a cumulative flank wear growth for a current time instant by summing the rate of change of flank wear width( dVB dt) for a plurality of cuts performed by the tool for a plurality of parts during the machining operation; and estimating, by the one or more hardware processors, the RUL of the tool at the current time instant from the determined cumulative flank wear growth( V B) and a maximum allowed value for the cumulative flank tool wear predefined for the tool. obtaining, by one or more hardware processors, a plurality of process parameters associated with machining process of a work piece, wherein the plurality of process parameters, comprising a spindle power ( S p), a radial depth of cut ( w) of the tool, an axial depth of cut t of the tool, and a cutting velocity V, are obtained directly from a Computer Numerical Control machine; deriving, by the one or more hardware processors, a rate of volumetric wear loss per unit contact area of the tool in terms of a rate of change of flank wear width ( dVB dt) of the tool, wherein the rate of change of flank wear width ( dVB dt) is computed using the spindle power ( S p), the radial depth of cut ( w), the axial depth of cut t of the tool, the cutting velocity V, predetermined constants A 1 and B 1 defined in accordance with a combination of the tool and material of the work piece, and a predetermined temperature wear coefficient ( K w), wherein the temperature wear coefficient K w considers effect of temperature rise due to friction caused by a current tool wear state of the tool during the machining operation; determining, by the one or more hardware processors, a cumulative flank wear growth for a current time instant by summing the rate of change of flank wear width( dVB dt) for a plurality of cuts performed by the tool for a plurality of parts during the machining operation; and estimating, by the one or more hardware processors, the RUL of the tool at the current time instant from the determined cumulative flank wear growth( V B) and a maximum allowed value for the cumulative flank tool wear predefined for the tool.