Process of forming openings

摘要

In a process using a hand-held drilling device for forming openings in a construction material containing steel reinforcing members, during the drilling step the electrical resistance between the drill bit and the reinforcing members is continuously measured. If the drill bit contacts the reinforcing member the measuring circuit is shorted out and the electrical resistance drops. The drop in resistance can be used as a signal for cutting power to the drilling device or for declutching or braking the device.