US Patent 10183339 Depth limiting drill

A depth limiting device for a drill includes a main body, an axial braking structure, and a limited shrinking structure. The axial braking structure is attached to the main body. The limited shrinking structure surrounds a drill rod of the drill, is slidably attached to the main body, and is in a home position or a compressed position. The axial braking structure axially brakes the drill rod such that the drill rod moves together with the depth limiting device. When the drill rod enters into a subject, the limited shrinking structure is pressed against the subject, moves from the home position to the compressed position, and stops the drill rod from entering further into the subject.