Which tool is specifically used to create cone-shaped depressions?

The tool that is specifically used to create cone-shaped depressions is known as a countersink. Countersinking is a machining process where a conical hole is cut into the workpiece, allowing for fasteners to sit flush with or below the surface of the material. The countersink tool has a specific angle that matches the head of the fastener being used, which ensures a precise fit and a smooth surface finish. This feature is particularly important in aviation industry applications, where aerodynamics and structural integrity are critical.

While other tools mentioned have their own unique functions, they do not serve the specific purpose of forming cone-shaped depressions. For instance, a mill file is primarily used for smoothing and shaping materials, but it does not create conical depressions. A lathe is a machine tool that rotates a workpiece to shape it, which can create various profiles but is not specialized for countersinking. An angle grinder is typically used for cutting or grinding materials and does not create the conical shape needed for a countersink.