| 摘要 |
PROBLEM TO BE SOLVED: To prevent the production of burr on a final outlet of the threading and dispense with the deburring by executing the chamfering work in advance with first, second and third end cutting edges and a thread cutting edge, and to improve the production efficiency by forming a prepared hole of a thread and cutting a female thread continuously after the chamfering work. SOLUTION: A chip 13 is formed by a three-layered body formed by sandwiching a second layer 31 made of a high-hardness sintered body between a first layer 32 and a third layer 33 made of a tool material, mounted on a shank 11, and further provided with a cutting blade 16. A first end cutting edge 24, a second end cutting edge 25 and a third end cutting edge 26, respectively producing fine chips, a thread cutting edge 22 for cutting the thread, and a flat drag 23 of a diameter same as an inner diameter of a female thread are successively formed on this order from a point of a drill toward the shank 11.
|
