Best Way to Cut Cast Iron Pipe - Renos 4 Pros & Joes (2023)

Today I completed a comparison between cutting 4-inch cast iron pipe with a reciprocating saw and an angle grinder to see which one was the best and the fastest. As a contractor and plumbing handyman in Atlanta, I do get requests for cast iron drain pipe repairs.

I recently completed a repair and I reminded myself that I needed to save a piece for this comparison. We will be cutting through 50+-year-old 4-inch cast iron drain pipe, complete with all the old nastiness inside (most of it is dry by now, but still).

Milwaukee vs Dewalt Tools

I am using a Dewalt corded angle grinder. This one is medium sized (its actually pretty big, but it’s not the ginormous one) and I have outfitted with a metal cutoff wheel. The reciprocating saw that I will be using is available here on Amazon.

I have everything set up on the edge of the woods in a picturesque setting and we are just about ready to begin. I will need to be able to stabilize the piece of cast iron that I will be cutting. In order to this, I will sit the section of cast iron pipe on my handy portable fold-up table. I will cut through the cast iron several times with each tool for time.

There are other tools that will cut cast iron, I am testing these two because they are tools that contractors, handymen, and homeowners commonly own.

The first time that I cut through the cast iron using the reciprocating saw it took me nearly 1 minute. I was cutting using basically only on hand. For the next round, I used two hands, so that I could better stabilize the pipe and so that I could apply more pressure and move the same more efficiently.

The second time trial resulted in a much lower time than the first with a time of 25 seconds. I learned my lesson, and I will use two hands to cut the third time as well. In the 3rd time trial, my time was nearly identical to the second run. I think I’ve done it about as fast as I can. Be sure to take a look at the reciprocating saw blade I used here on Amazon.

Now its time to move on to the angle grinder time trials. I set the cast iron pipe up on the table and I will stabilize it with my left hand as I cut. This is actually my first time cutting cast iron with an angle grinder. After i begin to cut the cast iron in my first trial run I notice sparks and dust flying everywhere. I stop for a moment because I realize that I am going to need additional (personal protective equipment).

Best Grinder Blade for Cast Iron

I pause the time trials and put on a long sleeve shirt, a pair of safety glasses, and respirator. Now I’m back. Let’s go! As I begin cutting with the angle grinder, it does a good job of cutting through the pipe. I then begin to move the grinder back and forth along the initial cut. As the cut seam expands and I get close to 180 degrees around the pipe, I have to roll the pipe over on the table in order to access the other side of the pipe. As I cut completely through the cast iron pipe for the first time with the angle grinder I look at the clock and it has taken me almost the same amount of time that it took me the first time with the reciprocating saw.

I’m optimistic about the second round because I think I can improve my cutting time with a few modifications to my technique. In the second time trial, my time drops, but only slightly. Its nowhere near where I had hoped. I set up for the third round to try and get closer to the reciprocating saw times. I cut through the pipe in the same way that I did the first two times and I got pretty much the same results.

In desperation, I decided to try a 4th time trial with the angle grinder. This time I am going to set the pipe on the ground with the end I’m going to cut pointing up. After two valiant attempts, I just can’t get it done. This one is a wrap!

Reciprocating Saw Vs Angle Grinder

After using both tools to cut cast iron back to back, I have a very clear understanding of the differences between these two tools.

The reciprocating saw allows you to cut straight through the pipe the way that you would cut butter with a butter knife. However, because I was budget conscious, I opted for the 6-inch blade and I did have to modify my cutting technique to keep the end of the blade from hitting the inner wall of the pipe during the cutting process.

This issue can easily be eliminated by purchasing the longer version of the blade either in the 9-inch version or the 12-inch version are both available on Amazon. I should add that I did adjust the guard on the front of my reciprocating saw and that seemed to pretty much eliminate the problem. However, cutting through 4 inch cast iron pipe is pushing the 6-inch blade to its limits due to its short length.

Being able to cut straight down through the cast iron is a major advantage because you are able to make a straight cut a lot more easily and you never have to change your sight line during the cut.

I also noticed that applying pressure to the reciprocating saw definitely allowed me to cut the cast iron faster. Cutting the cast iron with the reciprocating saw made very little dust, and the dust that it did make just fell to the ground.

Cutting with the reciprocating saw did not create any sparks.

Once I made my initial plunge cut with the reciprocating saw blade, the saw was very easy to control and pretty much cut in a straight line on its own after that.

Even Though I wasn’t paying very close attention, but I don’t recall the pipe getting very warm, as I cut it with the reciprocating saw.

Cutting Cast Iron with the Angle Grinder

After using the angle grinder to cut cast iron I have some key takeaways. As you can see in the video, I had to change into a long sleeve shirt when I began cutting with the angle grinder because of all the flying sparks. I also had to put on goggles and a respirator because of all the dust that the angle grinder created as it cut. And because it works with a spinning wheel, the grinder was compounding the dust issue by sliding it into the air.

I also noticed that there is a distinct difference between the way these two tools cut. The reciprocating saw with the carbide tipped blade literally cuts through the cast iron. The cutoff wheel on the other hand basically runs through the cast iron pipe. I noticed after my time trials that the spinning disc on the angle grinder was at least an inch smaller.

As I cut with the angle grinder I also noticed that the pipe was heating up.

Perhaps the most difficult part about cutting the cast iron with the angle grinder was trying to keep the blade going in a straight line and trying to rotate the grinder around the circumference of the pipe as I cut. This is because the angle grinder can only cut through half the pipe at most without having to rotate the pipe 180 degrees or flip the saw to the other side of the pipe.

Based on this experience, I would only use the angle grinder if I didn’t have access to a reciprocating saw and I was going to be cutting in an area where dust was not an issue.

Reciprocating Saw Blade for Cast Iron

Another big difference maker was the blades. I used a carbide tipped reciprocating saw blade designed for cutting cast iron and thick metals. Available here on Amazon. This blade is a significant improvement over the diamond grit blades that have been used to cut cast iron for years. This blade actually cuts through the cast iron as opposed to the diamond grit blade, which rubs through the iron much like the angle grinder cut-off wheel.

If the carbide tipped blade was not an option I would still select the diamond grit blade and reciprocating saw over the angle grinder and cutoff wheel. The reason is that the reciprocating saw is easier to control, and gives you the flexibility to cut in more areas. And even though they work with the same grinding principal, the reciprocating saw will create less dust because the saw moves back and forth instead of spinning.