Which tool is least likely to be used for driving pop rivets?

The least likely tool to be used for driving pop rivets is the bucking bar. A bucking bar is primarily utilized in aircraft and metalworking applications to provide support behind the material while performing riveting operations. It is often used in conjunction with a hammer or a pneumatic gun to set solid rivets rather than pop rivets.

Conversely, the other tools listed are specifically designed for driving pop rivets. A rivet gun, for example, is designed to set pop rivets effectively by pulling the mandrel through the rivet, achieving the necessary tension to secure the materials together. Similarly, a pneumatic gun operates using compressed air to drive the rivet, making the process faster and requiring less manual effort. A hand riveter is a manual tool that is also used to pull pop rivets and is widely employed in home and light industrial applications for its simplicity and effectiveness.

Thus, while a bucking bar plays a role in the overall riveting process, it does not actively drive pop rivets, making it the least suitable tool for that specific task.