Core drill bit of partially circular section - has secant shaped cutting edge and tapered lateral projection spaced around periphery of drill shaft

摘要

A cutting tool, esp. a core drill, comprises a hollow shaft and a cutting head equipped with inserted cutting elements. Each cutting element comprises a basically circular shape in cross-section and is inserted and fixed in an end bore in the cutting head. Pref. the principal cutting edge is a secant, esp. a dia. of the circular section. There is also pref. a taper from the rear end to the forward end of a portion additional to this secant. This produces a tapering surface, pref. at =90 deg. to the rake surface. The rake angle is specif. 4 deg. plus-or-minus 2 deg. The side rake is approx. 0 deg.