Depth gauge for electric hammer drill - uses light beam reflected onto photoelectric cell from surface being drilled

摘要

a depth gauge for a hand held electrically driven power drill (1) uses a beam of light and a photo-electric cell. The device (3) is fitted to the housing of the drill and emits a beam of light onto the surface being drilled. The position of the device can be adjusted so that when the hole has been drilled to the required depth the reflected beam impinges on a photo-electric cell which emits a signal. This signal is then used to switch off the drill motor. The idea can be adapted to use a beam of ultra-sonic vibrations.