TREPANNING TOOL

PROBLEM TO BE SOLVED: To effectively discharge chips outside without causing coiling and plugging by the chips.SOLUTION: A blade 112 attached to a tip end of a cylindrical part of a trepanning tool includes a chip breaker face 112d as well as a cutting edge 112c, a rake face 112a and a flank face 112b. The chip breaker face 112d forms a recessed curved surface smoothly continuing to the rake face 112a and pushes out the chips g flowing along the rake face 112a to the front of the advance direction α of the blade 112. The pushed-out cutting chips g are segmentalized in collision with a cut surface W2, and so on and effectively discharged outside without causing coiling and plugging.