| 摘要 |
PURPOSE:To improve the rigidity of a base metal, enable bushless machining, and improve the accuracy of a hole by forming the lubricating hole of a drill into an elliptical sectional area having a long shaft in the peripheral direction. CONSTITUTION:Lubricating holes 32 having elliptical sectional areas to which long shafts are provided in the peripheral directions of a base metal are provided on the base metal 12 of a drill 31. The outside diameter of the base metal 12 and the lubricating holes 32 are formed by means of drawing. Hence, as compared with the perforation by means of a gun drill, the bending of the hole and the like is not generated while enabling the wall thickness of the parts between the outer peripheral parts 20 and chip discharging grooves 15, and the lubricating holes 32 to be formed thick eliminating dispersion. Accordingly, the rigidity of the base metal 12 can be improved while improving the accuracy of the holes, enabling increase in oil quantity.
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