To provide a work machine capable of settling problems of workability due to difficulty of common use and fix a work jig and driving force due to difficulty of spot facing work for welding in a conventional work machine in a boring machine for piping and a boring method of the piping for boring a hole in a cylindrical boiler feed water pump inner peripheral surface always requiring warming-up.

This boring machine for the piping is composed of an installing jig performing centering in the axial direction of a drill and a hole bored in an external casing of a boiler feed water pump, fixed to the external easing by spot welding and arranging a slided plate parallelled with the hole in a tip part, a slide head fixed to the slide plate and provided with a feed screw rotated by a feeding hydraulic motor and a warming boring machine vertically moving by the feed screw by sliding along the slide head and installing the drill for boring the hole by a main spindle driving motor in the tip part. Thus, the installing jig can be used in common to the external casing of respective sizes, and can be sufficiently fixed by the spot welding to an external casing inner peripheral surface, and the hole axis and the drill axis are not dislocated without looseness by vibration so that boring work can be smoothly performed.