| 摘要 |
A drill apparatus with an electromagnet base, which has an electric drill directed downwards, is provided with an electromagnet base having an electromagnet for attaching the apparatus to a to-be-worked object by magnetic force. The electric drill is rotated by a drill motor and moved by a feed motor towards the object. A Hall element is situated on the electromagnet base. Two comparators detects whether or not a Hall voltage output from the Hall element falls in a predetermined range of voltage values. When the Hall voltage does not fall in this range, a transistor is turned on. Consequently, a relay is operated, a contact is opened, and power supply to the drill motor and the feed motor is stopped. |
