| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill which starts an excitation device automatically when concrete or the like is bored and is excellent in boring function and operability. SOLUTION: The excitation device A giving vibration in the axial direction of the drill bit 4 of the drill, a detection means 21 detecting the rotational frequency of the drill bit 4, and a control part 20 controlling the rotation of the drill bit 4 based on the detection results of the detection means 21 are provided. The control part 20, when recognized that the rotational frequency of the drill bit 4 is decreased for a prescribed length of time after the rotational frequency is increased, starts the operation of the excitation device A. COPYRIGHT: (C)2008,JPO&INPIT
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