| 摘要 |
A core cutter comprises a cylindrical base, a plurality of cutting portions provided at a tip end of the base, discharge grooves configured to discharge chips cut by the cutting portions, and an attaching portion. Each of the cutting portions 2 includes a block and at least three cutting blades. A first cutting blade 2a may be located radially inward relative to the second and third cutting blades 2b and 2c and the second cutting blade 2c is located between the first and third cutting blades in a radial direction, and the cutting blades deviate rearward in a rotational direction. A wall 3b of the discharge groove 3 corresponds to a cutting surface 2k of the third cutting blade, and a gallet 4 is provided adjacent each cutting portion, the gallet formed by cutting an outer peripheral surface of a tip end portion.
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