An exhaust pipe expander is a tool used during exhaust system installation and repairs. Exhaust pipes are made of thin steel that easily gets bent or crimped out of round when clamped or cut. When you want to slide one pipe inside another to create a splice, the pipes must be perfectly round and have the correct diameter. The expander is inserted into the pipe end and turned with a wrench to stretch the metal outward.
The tool consists of a series of stepped metal collets arranged around a central wedge shaft. As you turn the drive bolt, the wedge pushes the collets outward, applying heavy, even pressure against the inner walls of the pipe. This removes dents, reshapes squashed pipe ends, and flares the pipe slightly so a new pipe of the same size can slide in. Apply a small amount of heat to the pipe to make stretching easier and prevent the steel from cracking.