Three Ways to Cut Cast Iron Pipe

Method #1: Hacksaw
 
Although a homeowner can use a hacksaw to cut through a piece of cast iron pipe, this is the slowest and most difficult method available. Using a hacksaw to cut through a cast iron pipe will often require multiple blades and should be reserved when it is the only option available.
 

Method #2: Cold Chisel
 
Using a cold chisel to cut through a cast iron pipe is much more efficient than using a hacksaw, but requires considerably more skill. A ball peen hammer and cold chisel are among the most difficult hand tools to use accurately and effectively, making this a frustrating endeavor for the amateur. In addition to this hindrance, the cold chisel method for cutting cast iron pipe only works when you have access to all sides of the pipe and enough room to maneuver your chisel.
 
To use this method, draw a line using some chalk around the pipe where you wish to cut it. Using the cold chisel, start making small marks around the diameter of pipe along the chalk line. Because cast iron is brittle, the pipe should split after a few rotations over the same line.
 
Although many cast iron pipes will break cleanly using the cold chisel method, a jagged cut is also not unusual. This may not be an issue depending on your reason for cutting the pipe, but if you wish to create a smoother cut you should be able to remove any jagged pieces with an adjustable wrench and hammer.
 

Method #3: Snap Cutter
 
If you have more than a single cut to make, renting a snap cutter is well worth the cost. This is the only method that plumbers use when working with cast iron pipe. Despite its name, a snap cutter does not really cut so much as break the pipe at the designated location. Made up of a piece of roller chain and a ratchet, the chain is placed around the pipe where it exerts even pressure around the pipe. As the pressure increases the wheels embedded in the chain bite into the cast iron until it snaps.
 
    A snap cutter almost always creates a smooth cut and is by far the quickest method to cut cast iron pipe. Often this tool can be rented at a home improvement center if you cannot justify purchasing one for a small job.