Cutting tool and method for machining workpiece

A machining method for machining a hole formed in a workpiece, comprising the steps of:

• (i) preparing a tool comprising a shaft-shaped tool body having a first end which extends along a central axis and which is for attachment to a spindle of a machine tool, and a second end on a side opposite the first end, and a tip connected to the second end of the shaft-shaped tool body, the tip having a plurality of blade parts in the circumferential direction,
• (ii) attaching the tool to a spindle of a machine tool,
• (iii) arranging the tool relative to an aperture of the hole formed in the workpiece at a tilt angle, which represents an angle between a movement direction of the tool and the central axis of the tool, of 120 to 240° when viewed in a direction of a line perpendicular to a surface to be machined,
• (iv) moving the tool along an inner surface of the hole from the aperture of the hole toward the interior thereof to machine the inner surface,
• (v) returning the tool from the interior of the hole toward the aperture in a state in which the tool is separated from the inner surface of the hole, and
• (vi) moving the tool along a peripheral edge of the aperture of the hole at a predetermined pick feed, wherein
• steps (iii) to (vi) are repeated multiple times.