You have a choice of methods when cutting cast-iron pipe. You can use a hacksaw, but it is slow work. You can also use a chisel and ball-peen hammer. But when professionals cut cast iron, they use a snap-cutter. As its name implies, this tool snaps-breaks-a pipe in two. It consists of a roller chain that has hardened steel wheels built into it. The chain is connected to a ratchet or scissor head. As you lever the head, the chain tightens, and the cuter wheels bite into the pipe with equal pressure. Eventually the pipe snaps in two.
The tools and materials you will use: Cast-iron pipe, ball-peen hammer, cold chisel or snap cutter, adjustable wrench, work gloves.
Step 1: The low-tech approach to cutting cast iron pipe is to use a ball-peen hammer and a cold chisel. Begin by clearly marking the circumference of the pipe. Then score around the entire line with the chisel, until the pipe breaks in two.
Step 2: The pipe doesn't always break evenly when you use the cold chisel method. But any jagged section can be broken off using an adjustable wrench. Adjust the jaws so that they are slightly wider than the thickness of the pipe.
Step 3: A snap cutter is the easiest way to cut cast iron pipe. This rental tool has a chain that's attached to a ratchet mechanism. To use it, position the chain around the pipe at the cut line; then tighten the ratchet until the pipe breaks.