| 摘要 |
PURPOSE: An insert drill is provided to prevent a joint bolt from separating at a coupling hole by forcedly jointing a drill blade part into a bottom of the installing groove. CONSTITUTION: A main cutting blade(11) and a web cutting blade(12) are formed at an upper end portion of the drill blade part(10). An inserting part(13) is formed at a lower end portion of the drill blade part(10) in a predetermined length. The drill blade part(10) is inserted into a distal end portion(21) of an installing groove(22). An inserting groove(23) is formed in the installing groove(22). The inserting part(13) of the drill blade part(10) is inserted into the inserting groove(23). A connecting hole(24) for connecting the joint bolt(25) is eccentrically formed at a side portion of the distal end portion(21) corresponding to the inserting groove(23). A spiral flute(26) is formed at a circumference of a drill body(20) in a determined depth. A taper groove(14) is formed at one side of the inserting part(13) of the drill blade part(10).
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