PURPOSE: To ensure the easy setting of a chamfering tooth having a cutting edge at the end thereof to a drilling tool, and enable the easy setting of the chamfering tooth even to a tool of different shape simply via partial exchange by causing the chamfering tooth to be engaged with a mounting recess and a drilling tool groove.

CONSTITUTION: When drilling and chamfering are undertaken, using a burnishing drill 2 fitted with a chamfering cutter 1, a hole can be smoothly drilled, without hindering the discharge of chips from a drill groove 5. When the burnishing drill 2 is made to advance, the cutting edge 16 of a chamfering tooth 14 comes in contact with the open edge of a hole H and a recess Ha can be formed. Also, the chamfering tooth 14 is properly positioned at the burnishing drill 2, and rotated integrally therewith. The machining of a workpiece W can be machined with the cutting edge 16 of the chamfering tooth 14. The chamfering cutter 1 can be easily set to the burnishing drill 2 for use. Also, the recess HA can be formed at the open edge of the hole H, subsequent to the process of drilling and finishing the internal surface of a drill with the burnishing drill 2.