| 摘要 |
A gun drill is capable of supplying a coolant sufficiently to a cutting region even when a cutting blade or a guide pad is of a brazed type, or when an opening angle of a cutting chip discharge groove is large or when a tool diameter is small and of achieving high cutting efficiency by discharging cutting chips efficiently from the cutting region. The gun drill includes coolant supply passages inside a tool shank and inside a cutting head. A lengthwise direction linear cutting chip discharge groove on an outer circumferential surface extends from a proximal side of the tool shank to a cutting head distal end. The cutting head is formed with a coolant lead-out groove extending from a head-lengthwise direction intermediate portion to the head distal end, at an outer circumferential surface portion at a back side relative to the cutting chip discharge groove. A coolant lead-out port communicating with a coolant supply passage is open at a proximal end side of the coolant lead-out groove. |
