What tool is commonly used to cut off the head of a rivet?

The correct choice is the cold chisel, which is specifically designed to cut metal, making it well-suited for removing rivet heads. A cold chisel has a hardened edge that enables it to withstand impact and effectively slice through metal when struck with a hammer.

When cutting off rivets, precision and control are essential to avoid damaging the materials or structure around the rivet. The cold chisel allows the worker to target the rivet head directly and use hammer strikes to carefully sever it from the rest of the structure.

Other tools listed, such as the hack saw, are generally intended for cutting through longer sections of metal rather than specifically for rivets. A pry bar is designed for leverage and lifting, making it unsuitable for cutting tasks. A rivet gun is actually used to install rivets, not to cut them off, so it does not fit the required function of this task.