Removable tip type rotary tool

A removable tip type rotary tool comprising:

• a body forming a shaft shape, the body having a screw hole disposed concentrically with a shaft center and a fluid supply path disposed in communication with the screw hole;
• a tip concentrically attached to a leading end portion of the body in a removable manner, the tip being rotationally driven around the shaft center along with the body for predetermined processing, the tip being disposed with a mounting hole penetrating through the shaft center of the tip;
• and
• a mounting screw penetrating the mounting hole of the tip and screwed into the screw hole of the body to integrally fix the tip to the body, the removable tip type rotary tool being configured to dispose one and the other of opposing surfaces of the body and the tip are disposed with a rotation stop key and a key groove each having a triangular shape with a cross section symmetric relative to the shaft center in the direction orthogonal to the shaft center, fastening by the mounting screw bringing a pair of side surfaces of the rotation stop key and a pair of side walls of the key groove into close surface contact with each other,
• a total angle α for each of the pair of the side surfaces of the rotation stop key and the pair of the side walls of the key groove is within a range from 60 degrees to 100 degrees, a groove bottom of the key groove is rounded with a radius RA within a range from 1.5 mm to 2.8 mm, corners of opening edges on both sides of the key groove and comers of both base-end side portions of the rotation stop key being rounded with radiuses RB and RC, respectively, within a range from 1.5 mm to 2.8 mm,
• the removable tip type rotary tool being configured to be disposed with a fluid introduction path guiding fluid supplied from the fluid supply path into the screw hole toward the tip, and to have a leading end side discharge passage discharging the fluid to an outer circumferential side from a leading end side relative to a center of the tip in axial direction and a base end side discharge passage discharging the fluid to the outer circumferential side from a base end side relative to the center,
• the rotation stop key being configured to be disposed on the opposing surface of the tip, the rotation stop key having a leading end disposed with a retraction surface away from a bottom portion of the key groove, and a gap between the retraction surface and the key groove acts as the base end side discharge passage.