PURPOSE: To prevent a shaft core adjusting condition from being destroyed by constituting shaft part engaging units as an engaging unit engaged with fellow shaft shape members by means of their relative slide in the direction crossing at right angles to the shaft core direction of the shaft shape members, and arranging positioning means to position/support the shaft core adjusting condition in abutting parts of the shaft part engaging units.

CONSTITUTION: Cylindrical members 6A and 6B constituting a cylindrical body 6 provided with a cutter 5 and a pipe inside surface receiving member 10 on the tip side are connected by means of device body engaging units 8A and 8B so as to be rotatable freely in one united body, and shaft shape members 7A and 7B constituting a shaft shape body 7 inserted into the cylindrical body 6 are connected by means of shaft part engaging units 9A1 and 9B1 so as to be operated freely in one united body. The shaft part engaging units 9A1 and 9B1 are constituted as an engaging unit engaged with fellow shaft shape members 7A and 7B by means of their relative slide, and positioning means 15A and 15B to position/support a shaft core adjusting condition are also arranged in abutting parts of the shaft part engaging units 9A1 and 9B1.