| 摘要 |
PURPOSE: A drilling tool guarantees a long lifetime and stability of boring, even in case of diameter less than 0.4mm. CONSTITUTION: A drilling tool comprises a tool body and a plurality of spiral-shaped chip discharging grooves. . One or more cutting blades are installed on the leading end of the tool body. The spiral-shaped chip discharging grooves are formed from the leading end toward the base end of the tool on the outer periphery of the tool body. The chip discharging grooves comprise at least one main groove(2a) and one sub groove(2b). One or more of sub grooves are joined to a middle part of the main body. A step(7) is formed in a joined part of the main and sub grooves.
|
