HOLE DRILLING MACHINE AND METHOD FOR DRILLING OVAL HOLE AND INNER-DIAMETER-CHANGING HOLE BY MEANS OF HOLE DRILLING MACHINE

Provided is a hole drilling machine and the method for drilling an oval hole and an inner-diameter-changing hole by means of the hole drilling machine, the machine and the method being configured so that the oval hole can be shaped with high accuracy and drilling of a complicated hole such as the inner-diameter-changing hole can be performed with high accuracy. A hole drilling machine 100 includes a spindle 101 and an auxiliary spindle 120 holding both end portions of a processing tool 102 having a cutting blade 103. The spindle 101 includes a spindle drive motor 106 configured to rotatably displace the processing tool 102 on a circular path, and a tool turnable-drive motor 105 configured to spin the processing tool 102. The auxiliary spindle 120 includes an auxiliary spindle drive motor 120b. In the auxiliary spindle drive motor 120b, a tool fitting portion 120a in which a tip end portion of the processing tool 102 is slidably fitted is synchronously rotatably driven on the same circular path as that for the spindle 101. A table reciprocatably-displacing mechanism 111 is provided between the spindle 101 and the auxiliary spindle 120. The table reciprocatably-displacing mechanism 111 reciprocatably displaces a work piece WK in an X-axis direction perpendicular to an axial direction of the spindle 101.