| 摘要 |
A device for determining when a drilled hole has reached a pre-set depth, comprises a light emitting device 1, a power source, and a control switch attached to the body of a drilling machine 2. The device projects at least one visual reference mark 5 on a drilling tool 4 at a pre-set distance from a drill tip 8 equal to the required hole depth 9. The reference mark advances towards a workpiece 10 during drilling, and indicates that the pre-set depth has been achieved when it coincides with the surface of the workpiece. Preferably, the position of the light mark on the tool can be varied. A computing device 13 may be provided to convert the movement of the light source into a measurement displayed on a visual display 14. A mirror (15, fig 3) reflecting a continuously pulsed laser beam may be used to produce a number of visual graduations on the tool. |
