| 摘要 |
Provided is a drill head for deep-hole drilling which does not generate such a disc that clogs a cutting chip discharge port when a head main body of the drill head penetrates a work material. The drill head is mounted with a central cutting blade tip 6 at the head center portion so as for a blade edge 6a thereof to be inclined downward toward the head center portion, a circumferential cutting blade tip 7 at a circumferential portion so as for a blade edge 7a thereof to be inclined upward toward the head center portion, and an intermediate cutting blade tip 8 therebetween so as for a blade edge 8a thereof to be inclined upward toward the head center portion, while the cutting blade tips face a cutting chip discharge port 4 or 5. The drill head includes a head main body 2 having an interior hollow portion 3 serving as a cutting chip discharge passage which communicates with the discharge ports 4 and 5. A disc breaker 12 composed of an inclined surface inclined downward toward the head center portion is formed at a head center side end portion of a flank 8b of the intermediate cutting blade tip 8 inclined upward toward the head center portion.
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