THROWAWAY DRILL, INSERT FOR THROWAWAY DRILL, AND CUTTING METHOD USING THE THROWAWAY DRILL

摘要

A throwaway drill, an insert attached to the throwaway drill, and a cutting method using the throwaway drill. The throwaway drill has an inner edge insert pocket formed on the center axis side at an forward end section of a drill body and having a seat surface, a throwaway drill holder formed on the outer peripheral side of the forward end section and having an outer edge insert pocket having a seat surface, an inner edge insert fixed to the seat surface of the inner edge insert pocket, and an outer edge insert fixed to the seat surface of the outer edge insert pocket. When viewed from the forward end of the drill body, an inner cutting edge of the inner edge insert includes a first inner cutting edge provided on the center axis side of the drill body and in parallel with at least some of outer cutting edges of the outer edge insert, and also includes a second inner cutting edge provided on the outer peripheral side of the drill body and tilted to the seat surface side of the inner edge insert pocket, from the first inner cutting edge toward the outer peripheral side.