| 摘要 |
The present invention provides a gun drill having excellent cutting efficiency, by which the cutting rate can be further significantly improved in comparison with conventional gun drills, having high deep-hole drilling efficiency, and having a prolonged blade service life, capable of reducing the frequency of polishing for re-use in a case of a small diameter. The gun drill is provided with a cutter head 3A having a coolant discharge port 11 communicating with a coolant supplying path 12 at the distal end face 3a at the distal end 1b of a hollow shank portion 1 having a cutting chip discharge groove 11, whose section along the lengthwise direction is V-shaped, on the outer surface and having the interior thereof made into a coolant supplying path 12, wherein a blade portion 32 of the cutter head 3A is made of cemented carbide alloy W, and at the same time, the guide pads 5A and 5B that are brought into sliding contact with the inner circumference of a cutting bore are composed of a dissimilar material having higher hardness than the cemented carbide alloy W. |
