PURPOSE: To prevent a rotation of a main shaft, and to improve the performance by installing the main shaft which has installed a cutting tool to the lower end, to a rotary main body so as to execute a conical track motion, and also linking the head part of the main shaft to a frame through a universal joint.

CONSTITUTION: A rotary main body 4 is supported so as to be freely rotatable in the lower part of a frame 2 through bearings 3, 3a, a main shaft 6 is supported so as to be freely rotatable in an eccentric position of the rotary main body 4 at a prescribed inclination angle, and a cutting tool 8 in installed to the lower end part of the main shaft 6. A head part 9 of the main shaft 6 which has been supported by the rotary main body 4, and the upper end part of an intermediate shaft 11 are linked to the lower end part of the intermediate shaft 11 through a universal joint 10, and to the frame 2 through the universal joint 10 in the same way, respectively. According to this device, a rotation of the main shaft can be prevented by an action of the universal joint, therefore, a life of the cutting tool is extended, and a good caulked surface can be obtained.