| 摘要 |
PROBLEM TO BE SOLVED: To provide a cemented carbide coating drill with an oil hole which is suitable for drilling the hole having 10 times of the diameter of the drill while discharging a small amount of mist from the oil hole opened to the tip of the blade edge passing through the inside of a drill land, and prevents the occurrence of hole expansion, the curvature of the hole, or undulation by suppressing the curvature or meandering of the hole without requiring a complicated manufacturing method. SOLUTION: Two threads of chip discharge grooves 2 extending to a drill shank and a margin 3 having a pair of widths of 2.4 mm (40% of the diameter of the drill (it can be within 30 to 60%)) are formed on the outer peripheral surface of the drill body, and a main flank 13 and a sinning 4 continuing to a pair of main cutting blades 12 in the peripheral direction are formed at the tip. An inclined angleαof the sinning 4 is made to be 40°(it can be 40 to 50°) and the rear end 5 in the drill rotation direction is made to be overlapped (contact point 5) to the inclined surface of the sinning 4 to have two oil holes 6 at the land 8 along a drill helical angle. COPYRIGHT: (C)2008,JPO&INPIT
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