ROTARY TOOL

PROBLEM TO BE SOLVED: To provide a rotary tool capable of suppressing variations in processing amount for a workpiece even when a shape and fixed position of the workpiece vary.SOLUTION: In a rotary tool 10, a core shaft 20 is fitted in a base shaft 11, and the core shaft 20 is engaged with the base shaft 11 to be movable backward and forward by an engagement mechanism between engagement projections projecting from an inner peripheral surface of the base shaft 11, and engagement slide faces 24A for forward movement and engagement slide faces 24B for backward movement, which are formed on an outer peripheral surface of the core shaft 20. By a compressive-deformable member 54 contained in a variable reception chamber 53, a head part 21 is biased to an origin position which is intermediate in a backward and forward movable region of the core shaft 20 relative to the base shaft 11. With this, when load torque Tr is displaced by variations in shape and fixed position of a workpiece W, a head part 21 can be displaced backward and forward relative to the origin position.