| 摘要 |
<p>An insulated electrode member (17e) is disposed in proximity to the pressure receiving section (16a) of a rotor shaft (16), and a capacitor (C) is formed between the pressure receiving section (16a) and the electrode member (17e). When a current is supplied to a stator (19b) from an inverter power supply (20), an axial voltage is induced in the rotor shaft (16), and the axial voltage is also induced in the electrode member (17e) via the capacitor (C), and a detecting device (29) that detects the axial voltage is connected to the electrode member (17e). When a spindle is brought down, and the detecting device (29) cannot detect the axial voltage due to abutting of the leading end of a drill (5) on a work in the grounded state, said axial voltage having been detected, the detecting device outputs detection signals to an NC device (30). When the detection signals are inputted to the NC device (30), the NC device determines that the drill (5) is abutting on the work, and a hole is drilled by machining the work to a predetermined depth from the abutting position using the drill (5).</p> |
