| 摘要 |
<p>A gun drill in which coolant delivered to a cutting part can be discharged intensively to a chip discharge groove along with the chips, damage on the inner circumference of a drilled hole or fall of machining precision due to clogging with chips can be prevented, and cutting efficiency is enhanced by reducing rotary load and long lifetime can be attained. Coolant supply paths (10, 20) are provided in a tool shank (1) and a cutting head (2), one chip discharge groove (3) is provided in the outer circumferential surface from the proximal side of the tool shank (1) to the distal end of the cutting head (2), discharge ports (22a, 22b) communicating with coolant supply holes (21a, 21b) and a chip discharge groove (3) are provided in the distal end face (2c) of the cutting head (2), and annular protrusions (4a, ... ) are formed in the outer circumferential surface of the cutting head (2) continuously over the entire circumference while bridging above the chip discharge groove (3).</p> |
