| 摘要 |
PROBLEM TO BE SOLVED: To provide a cemented carbide coating drill with an oil hole which exerts both drill body rigidity and chipping discharging efficiency, prevents sudden breakage thereof due to clogging with chippings, and carries out stable machining. SOLUTION: The cemented carbide coating drill is formed of a first web thickness tapered portion 1, a second web thickness tapered portion 2, and a third web thickness tapered portion 3, in this order from a distal end to a proximal end thereof. The first web thickness tapered portion 1 extends from the distal end over a length of 50 mm that is 10 times a drill diameter, and the web thickness thereof is reduced beginning from the distal end at a high gradient of -0.4/100. The second web thickness tapered portion 2 continuously extends from the first web thickness tapered portion 1 on a rear side of the same over a length of 75 mm that is 15 times the drill diameter, and the web thickness thereof is reduced at an intermediate gradient of -0.2/100 that is smaller than the gradient of the first web thickness tapered portion 1. The third web thickness tapered portion 3 further continuously extends from the second web thickness tapered portion 2, and the web thickness thereof is reduced at a gentle gradient of -0.1/100 that is smaller than the gradient of the second web thickness tapered portion 2. Herein a grooving finishing portion 4 of the cemented carbide drill with the oil hole has a web thickness being 25% or more of the drill diameter. COPYRIGHT: (C)2008,JPO&INPIT
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