Hole drilling machine and method for drilling oval hole and inner-diameter-changing hole by means of hole drilling machine

A hole drilling machine comprising:

• a work table configured to hold a work piece having a lower hole in a through-hole shape;
• a spindle formed in a shape of a rod penetrating the lower hole of the work piece held on the work table and configured to spin a processing tool, which holds a cutting blade configured to cut the work piece, about an axis while holding one end portion of the processing tool to turnably displace the cutting blade about the axis and rotatably drive an entirety of the processing tool on a circular path about a center axis at a position eccentric with a center axis of spinning;
• an auxiliary spindle having a tool fitting portion in which the other end side of the processing tool is slidably fitted and configured to rotatably drive the tool fitting portion on a circular path parallel with the circular path for the spindle;
• a spindle displacement mechanism configured to displace the spindle and the work table relative to each other in a Y-axis direction as an axis direction of the spindle to decrease or increase a distance between the spindle and the work table;
• and
• a control apparatus configured to control actuation of each of the spindle, the auxiliary spindle, and the spindle displacement mechanism,
• wherein the control apparatus
• turnably displaces the processing tool while displacing the processing tool in the Y-axis direction in a rotatably-driven state, thereby shaping, at the work piece, at least one of an oval hole or an inner-diameter-changing hole of which inner diameter changes along a hole depth direction.