| 摘要 |
PURPOSE:To aim at enhancing the working efficiency, by providing a circuit for controlling a drilling motor and a feed motor so that the feed of an electrical drill is stopped for a predetermined time after overload occurs during drilling while chips are removed in order to enable smooth drilling. CONSTITUTION:A necessary drill 9 is secured to an electrical drill 3 while a rotational speed setting knob 8 is set to a position corresponding to the diameter of the drill 9, and then an electrical switch is turned on to energize an electromagnetic coil in order to attract a workpiece to be drilled. Then, a change-over knob 7 is turned to turn on an automatic switch to energize a speed control circuit so that a drilling motor 2 is rotated at a rotational speed corresponding to the diameter of the drill on use. Further, when the electrical drill 3 is lowered for drilling, the current running through the drilling motor increases, and when overload is detected, the feed of the electrical drill 3 is stopped for a predetermined time. With this arrangement chips causing an increase in load may be removed so that no overload occurs after refeed of the electrical drill 3, thereby it is possible to enhance the working efficiency. |
