| 摘要 |
A core drill which, even if used with a rechargeable electric drill having low rotational torque, can bore a hole and which allows the drill to bore a hole with less electric power consumption. A core drill has a thin-walled core body (2). The outer peripheral surface of the tip of the core body (2) is formed in a tapered surface so that the core body is thin and sharp pointed on the tip side thereof. A recess (2B) for embedding a cutting tip therein is formed in the peripheral edge of an opening in the tip. That portion of the core body which is adjacent to that portion of the recess which is located at the front in the rotational direction is bent inward radially. The cutting tip (3) is provided with a step section which is, in a bottom view, formed such that an inner diameter portion (3a) of a front end (3A) projects forward in the rotational direction and that an outer diameter portion of the front end is receded rearward in the rotational direction. The cutting tip is also provided with a step section which is, in a bottom view, formed such that an inner diameter portion of a rear end is located forward in the rotational direction and that an outer diameter portion of the rear end is located rearward in the rotational direction. The cutting tip (3) is mounted to the core body (2) such that the front end of the recess in the rotational direction is located at the inner diameter portion (3a) of the front end of the cutting tip in the rotational direction and that a connecting surface for connecting to each other the outer diameter portion (3c) and an inner diameter portion (3d) of the rear end in the rotational direction is in contact with the outer peripheral surface of that portion of the core body which is adjacent to that portion of the recess which is located at the rear in the rotational direction.
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