| 摘要 |
An annular hole cutter including a barrel and cutting teeth attached to a lower portion of the barrel. A portion of a cutting edge of the cutting teeth including hard teeth each having an outer cutting edge formed into a segment which is concentric with respect to an outer circumferential surface of the barrel and an inner cutting edge formed into a segment which is eccentric a slight distance with respect to an inner circumferential surface of the barrel in the radial direction. Eccentric regions of the hard tooth project from the inner circumference of the barrel in the centripetal direction. A gullet is defined between adjacent edges of the cutting teeth for the removal of chips. An inner peripheral surface of the hard teeth located above a stepped portion of the gullets each being formed into a segment which is concentric with respect to the inner circumferential surface of the barrel, and has the same radius of curvature as that of the inner circumferential surface.
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