A depth gauge device including a body extending a central longitudinal axisand including a channel and a light-passinghole, the light passing hole open to the channel, a light source mounted inthe body for generating a light beam, the light beam passingthrough the light- passing hole toward a surface of a drill-bit extendingthrough the channel, the light beam forming an incident lightbeam when reflected away from the drill-bit surface, an image sensor mountedin the body for sensing the incident light beam andgenerating a plurality of successive images of the drill-bit surface to detectvariations in the position of the drill-bit moving throughthe channel and an clamp coupled to the body, the clamp including a pluralityof adjustable arms configured to clamp the device toa protection sleeve.
