Bohrwerkzeugvorrichtung mit Zentrierbohrer und Hohlbohrkrone

摘要

A center drill used for machining a hole in a work piece which is adapted to be partially enclosed in a cup shape drill member in a side view thereof, includes a drill portion provided on a leading end of the center drill, and a dust extractor radially outwardly extending from a portion of the center drill which is enclosed in the cup shape drill member.