| 摘要 |
The present invention discloses a rotary cutting tool which can maintain a secure coupling state between the shank and the cutting head and enhance the durability of the shank by preventing a damage of the shank and the cutting head from being generated. In the rotary cutting tool according to the present invention, the cutting head comprises a central post in a cylindrical shape which is concentric with the rotating axis of the drill body and a plurality of wings formed at the upper end of the central post extending in the radial direction, each of the wings has an end surface, an upper surface, a lower surface, a forward surface which is facing the drill rotational direction, and a rearward surface opposite to the forward surface, the forward surface being provided with the chip flute extended over to the lateral wall of the central post, the lateral wall of the central post consisting of cutouts forming the chip flutes and the circular outer circumferential surfaces, the circular outer circumferential surface of the central post being provided with rotation guide element thereon extending in a circumferential direction. The coupling structural means comprises a plurality of coupling limbs extending from the circumferential portion of the tool shank in parallel with the rotating axis to provide a central opening therebetween for receiving the central post, each of the coupling limbs consisting of a torque bearing part in the upper portion and a frictional fastening part in the lower portion, the torque bearing part being provided on the side of the drill rotational direction with a recess delimited by an axial bearing surface and a torque bearing surface for resting one of the wings therein, the inner wall of the frictional fastening part having a transversal cross section of a circular arc such that the inner wall of the frictional fastening part has a surface contact with the circular outer circumferential surface of the central post, the inner walls of the frictional fastening parts being provided with coupling elements engageable with rotation guide elements of the central post.
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