| 摘要 |
<p>A heavy load is prevented from being applied to a small-diameter blade, in order to prevent service life reduction of the small-diameter blade. An electrical drill drives the annular blade to rotate, by having a drill motor (46) as a driving source. The electrical drill moves close to a machining object by means of a drill feed section having a feed motor (20a), and the machining object is drilled by the annular blade. In the drilling step, a motor current of the drill motor (46) is detected by a motor current detector (50). A main control section (64) compares the detection results obtained from the motor current detector (50) with previously set comparison value, identifies the blade diameter of the drilling annular blade, and sets control mode for each blade diameter in accordance with the identification results.</p> |
