PURPOSE: To perform favorable cooling and discharge of chips, by a method wherein a cutting member is mounted on the outer circumference of a rotary board, a spouting port is communicated with a cutting member side by passing through a communication hole of the rotary board from an opening part, the rotary shaft is fitted with a board and a rotary fan and a vent port of the rotary board and the opening part of the board are communicated with each other.

CONSTITUTION: A cutting members 34... are provided on the outer circumference of rotary board 30 of a disc, opening parts 32... taking in air are opened on the center side of the board, communication holes 31 are formed radially into the board by communicating with the opening parts 32..., and spouting ports 33... are opened in an outer circumferential side, in a rotary blade 3. An axial hole 45 is provided in the central part, vent ports 43... corresponding to numbers and positions of the opening parts 32 are provided on the circumference of the axial hole 45 and the vent ports 43 of the rotary fan 4 are clamped down to the opening parts 32 of the rotary blade 3. The rotary board 30 and rotary fan 4 are turned through a rotation of a rotary shaft 2, air is injected from an outer circumferential part side by passing through the communication hole 31 of the rotary board 30 by ventilation from the vent port 43 of the rotary fan 4, the cutting member 34 is cooled and chips are discharged.