What tool is used to cut external threads on an object?

The tool used to cut external threads on an object is a die. A die is a specialized tool that is designed to create threads on the outside of a cylindrical workpiece, such as a bolt or a rod. When a die is turned or pressed onto the material, it shapes the surface by cutting away the material to form the desired thread pattern. This action allows for the creation of precise and consistent threads, which are essential for ensuring that fasteners can be properly assembled and tightened.

Understanding the purpose of a die helps clarify its significance in mechanical engineering and manufacturing, where threaded components play a crucial role in joining parts securely. The other options listed serve different functions: a drill is used for making round holes; a tap is employed to cut internal threads within a hole; while a hacksaw is intended for cutting through materials, typically in straight lines, but does not create threads at all. Thus, the die is uniquely suited for external threading tasks.