Hole saw with hole enlargement guide and support piece detachable therefrom

A hole saw with hole enlargement guide and support pieces (50) detachable therefrom, comprising a drive shaft (12) mounted on a chuck of an electric drill (11), a nose bolt (16) and a nose flywheel (18) disposed on the front end periphery of the drive shaft (12), a flywheel nut (19) screw-coupled to the drive shaft (12) under the nose flywheel (18), a plurality of fastening rods (19-1) spaced apart from each other and fitted to the nose flywheel (18) to allow the underside ends thereof to be restrained onto the top surface of the flywheel nut (19), a hole saw body (20) screw-coupled and separated to and from the outer periphery of the nose bolt (16), a coil spring (15) and a dust scattering prevention cap (25) sequentially coupled to the drive shaft (12) formed integrally with the lower end periphery of the nose bolt (16), a conical fastener-fitting rod (30) formed integrally with the center of top end periphery of the nose bolt (16) and having a screw portion (31) formed on the upper end periphery thereof to allow the hole saw body (20) to be detachably mounted thereonto, a conical fastener-bouncing coil spring (35) first fitted to the conical fastener-fitting rod (30) from top side of the hole saw body (20), and a conical fastener (40) having the shape of a cone whose top becomes narrow and bottom becomes wide, fittedly coupled to top side of the conical fastener-bouncing coil spring (35), and having an insertion and removal hole (41) formed along the center thereof in up and down directions thereof, wherein the hole enlargement guide and support pieces (50) are spaced apart from each other at given intervals on the outer peripheral surface of the conical fastener (40) and detachably mounted onto the conical fastener (40) through a detachable part.