PURPOSE: To perform speedy and correct work of edge preparation in a narrow place, in case of using a jig for edge preparation of an existing piping end face, by screw fitting a cutter supporting shaft to the internal peripheral surface of a centering collar and always aligning the supporting shaft to an axial line of the piping.

CONSTITUTION: Two centering collars 6, almost equal to the inside diameter of a pipe 12 for edge preparation, are screwed to a cutter supporting shaft 2 from its both ends. Then the two centering collars 6 are inserted into a smaller contour part13 at both ends of the supporting shaft 2 and screwed to a screw part 3. Then after insertion of said collars 6 into the pipe 12, a spanner stopper part 14 of the supporting shaft in the outside of the pipe 12 is used with a spanner and turned counter clockwise, and the end of the centering collars 6 are press fitted into the end of a tapered collar 8 to spread the centering collar 6 and surely allow the periphery of the centering collar 6 to bite the internal periphery of the piping 12, then the cutter shaft 2 is set to the axial line of the pipe 12. And then, the spanner is removed, and a funnel shaped edge preparation cutter 1 is mounted to the end of the supporting shaft 2 in the outside of the pipe 12, then this cutter 1 is rotated to perform correct and speedy work of edge preparation for an opening end edge of the pipe 12.