A casing mill, comprising: an elongated main body having a bore and a means for attachment to a drillstring; a plurality of elongated cutter bases hingedly connected to said main body by a plurality of operating arms and movable between a first position substantially retracted to said main body, and a second position extended outwardly from said main body; a means for moving said cutter bases between said first and second positions; one or more cutters mounted on each of said cutter bases, said cutters positioned so as to be in cutting relationship with a casing string when said cutter bases are in said second position; characterised in that: wherein each of said cutter bases comprises a stabilizer section on a lower end thereof, wherein no cutters are mounted, said stabilizer section adapted to bear against an inner wall of a casing string when said cutter bases are in said second position; a radial dimension of said cutters extending outwardly from said cutter base and beyond an outer diameter of said casing string, when said stabilizer bears against said inner wall of said casing string, a sufficient distance to extend over any casing collar on said casing, and wherein a radial outward face of said cutter comprises a non-cutting surface; wherein one or more of said operating arms comprises an extended cutout arm which extends beyond the radial outermost position of said cutters when said cutter bases are in said second position, so that an outer end of said cutout arm contacts said inner wall of said casing string while said cutters are not in contact with said inner wall, said cutout arm comprising a hardened cutting surface to enable cutting through said casing. an elongated main body having a bore and a means for attachment to a drillstring; a plurality of elongated cutter bases hingedly connected to said main body by a plurality of operating arms and movable between a first position substantially retracted to said main body, and a second position extended outwardly from said main body; a means for moving said cutter bases between said first and second positions; one or more cutters mounted on each of said cutter bases, said cutters positioned so as to be in cutting relationship with a casing string when said cutter bases are in said second position; characterised in that: wherein each of said cutter bases comprises a stabilizer section on a lower end thereof, wherein no cutters are mounted, said stabilizer section adapted to bear against an inner wall of a casing string when said cutter bases are in said second position; a radial dimension of said cutters extending outwardly from said cutter base and beyond an outer diameter of said casing string, when said stabilizer bears against said inner wall of said casing string, a sufficient distance to extend over any casing collar on said casing, and wherein a radial outward face of said cutter comprises a non-cutting surface; wherein one or more of said operating arms comprises an extended cutout arm which extends beyond the radial outermost position of said cutters when said cutter bases are in said second position, so that an outer end of said cutout arm contacts said inner wall of said casing string while said cutters are not in contact with said inner wall, said cutout arm comprising a hardened cutting surface to enable cutting through said casing. wherein each of said cutter bases comprises a stabilizer section on a lower end thereof, wherein no cutters are mounted, said stabilizer section adapted to bear against an inner wall of a casing string when said cutter bases are in said second position; a radial dimension of said cutters extending outwardly from said cutter base and beyond an outer diameter of said casing string, when said stabilizer bears against said inner wall of said casing string, a sufficient distance to extend over any casing collar on said casing, and wherein a radial outward face of said cutter comprises a non-cutting surface; wherein one or more of said operating arms comprises an extended cutout arm which extends beyond the radial outermost position of said cutters when said cutter bases are in said second position, so that an outer end of said cutout arm contacts said inner wall of said casing string while said cutters are not in contact with said inner wall, said cutout arm comprising a hardened cutting surface to enable cutting through said casing.