PURPOSE: To eliminate the need of manufacturing exclusive parts for many kinds of stator cores different in inside measurement and number of slots by constituting the blades circumferentially and radially mobil by means of the first and second driving mechanisms.

CONSTITUTION: To a base substance 25 pivoting members 30 and 31 are provided which are circumferentially mobil with a supporting point 29 in its center on the central axial line of a stator core 22. Blade holding members 36 and 37 are attached to pivoting members 30 and 31 mobil in radial direction of the stator core 22. The pivoting members 30 and 31 and blade holding members 36 and 37 are driven by the first and second driving mechanisms 32 and 39. Thus the blades 46 and 47 are moved in circumferential and radial directions of the stator core 22.