A processor implemented method for monitoring tool wear to estimate Remaining Useful Life (RUL) 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 (CNC) 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(VB) 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 (CNC) 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(VB) 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 . <EOS>