How to Cut Cast Iron Pipe with an Angle Grinder?

Up until the 1970s, the go-to material for pipework was cast iron. However, because of its proneness to developing rust and the installation issues its heavyweight brought about, it was replaced by ABS and PVC pipes.

If you own an older home, there’s a good chance that your plumbing system is made of cast iron, and you might find yourself dealing with leaks sooner or later.

Luckily, replacing cast iron pipes is possible and not overly complicated. If you’re an avid DIYer, then you probably have an angle grinder at home that you can use to swiftly cut as many pipe segments as you need.

To cut a cast iron pipe with an angle grinder, you must first secure the pipe with a clamp-on your workbench/table. You must then turn on the angle grinder and safely cut around the cast iron pipe to create a straight, flat, and clean-cut. You can trace out a straight path around the pipe before cutting if you feel that would help you cut straighter!

Can an angle grinder cut cast iron?

Angle Grinder

Yes, you can cut cast iron with an angle grinder, but not every angle grinder will do. Cheap, low-quality grinders lack the strength necessary to cut through dense materials such as cast iron. You might want to consider upgrading your angle grinder to a heavy-duty model if you wish to successfully tackle thicker materials.

Now, if you’ve had your grinder for a while, then you probably already know that for each task you want to carry out, you need a specific disc or wheel.

For any first-timer who has just come across this tool, angle grinders have round accessories that are attached to the head. They’re usually called discs, or wheels when they’re thicker than ½ inch, and they’re the ones in charge of the cutting, grinding, polishing, smoothing, and so on.

Well, cutting cast iron is no exception, so you can read the following section to find out which type of attachment you’re going to need.

What attachment do I need to cut cast iron with an angle grinder?

To successfully slice through cast iron pipes like butter, you need to equip your angle grinder with the right attachment. Any seasoned handyman can tell you that using the proper equipment not only prevents accidentally damaging your workpiece, but also helps you work safely more efficiently.

Wheels come in different grains, bonds, and thicknesses, and it’s important to choose one that’s strong enough for the job at hand.

If you have a decent metal cutoff wheel, you can use it to cut cast iron pipes. However, keep in mind that there’s a risk it might shatter if it’s poor quality or if you apply too much pressure to it. They’ll also cut slower and generate more friction.

The best option if you want to cut cast iron with an angle grinder is to invest in a 4-inch diamond wheel. This type of wheel has a steel core with a very sharp edge made of synthetic diamonds that are perfect for getting through tough materials.

If you’re buying a wheel, make sure you get the correct size to fit your grinder, and that the maximum RPM of the wheel is higher than that of the tool to prevent damaging either of them or injuring yourself.

How to use an angle grinder to cut a cast iron pipe

Angle grinders are extremely versatile pieces of equipment that can be used for a wide variety of purposes, ranging from sharpening a dull blade to grinding concrete blocks. Each use requires that you learn and apply specific techniques to achieve the best results.

So, let’s start with the safety measures you should take.

Getting ready

Angle grinders are so fast and easy to operate, that many people choose to forgo safety measures to finish their project as quickly as possible. Big mistake! All power tools can be dangerous if not handled properly, and grinders are no exception, especially if you’re cutting metal.

To prevent any accidents and injuries, you should always wear your personal protective equipment (PPE). A complete gear for cutting cast iron pipes should include:

  • Safety goggles – to protect your eyes from sparks and debris produced by cutting.
  • Earmuffs – to protect your ears from the loud noise produced by the grinder.
  • A dust mask or face shield – to avoid inhaling any fumes or dust produced while cutting.
  • Gloves – for a better grip and to prevent accidental cuts on your hands.
  • Safety boots – to protect your feet from any pieces of metal that might fly down after cutting them.
  • Tightly fitting clothing – to prevent fabric from getting caught by the disc.

We highly recommend that you read the manufacturer’s instructions if you haven’t yet, as different angle grinder models might require additional safety precautions.

Preparing your workspace, grinder, and cast iron pipe

Man Angle Grinding

Good and safe practices also include securing your workspace, your tool, and the piece you’re working on.

First of all, you should declutter your workspace, paying special attention to the floor and any elements that might get tangled in the power cord, to prevent any accidents and avoid tripping and falling.

Next is readying your angle grinder before plugging it into the power source. Simply open the spindle to insert the wheel, and then fasten the spindle nut in place.

Make sure that both the tool and the wheel are in sound condition before using them. Start the grinder and run it for about 30 seconds to check that everything is secured and works as it should.

Finally, finish your preparations by marking your cut and stabilizing your workpiece. For the former, you can use chalk, but we recommend that you wrap a strip of masking tape around the pipe to provide a straight edge you can follow with the wheel.

Cutting unsupported pieces is extremely dangerous, especially when they’re as heavy as cast iron. If the pipe is positioned vertically, you should secure it with a riser clamp attached at ground level to control the drop of the pipe piece after you’ve cut it. Cast iron pipes that are placed horizontally should be supported by a pipe hanger approximately every 5 feet (1.5 m).

Riser clamps are a two-point device that clamps around the pipe with bolts at each floor level of a building to take a portion of the pipe load. Pipe hangers are metal support mechanisms that transfer the pipe load to the supporting structures.

Now we’re ready to start cutting cast iron pipes with an angle grinder!

Cutting the cast iron pipe

Cutting cast iron pipes with an angle grinder can be a bit trickier than cutting other metals because they’re usually located in tight or hard-to-reach spaces (more on this in the next section), but the process is rather straightforward.

  1. Adjust the blade guard so that it’s positioned between your body and the tool.
  2. Once you turn the angle grinder on, allow the disc to reach full speed to achieve smoother and better results. This shouldn’t take longer than 60 seconds.
  3. Holding the tool firmly with both hands, set down the wheel lightly on the chalk mark or the masking tape while holding a 90° angle.
  4. Score a grove that wraps around the diameter of the pipe, about ⅛-inch deep.
  5. Once the grove is done, guide the grinder to penetrate the pipe through a single point and keep working around the piece until the cut is finished.
  6. Turn the grinder off and grab a cold chisel. Drive it through the last remaining connection point with a ball-peen hammer to snap it off and release the pipe section.

And that’s it, you’ve successfully cut that prehistoric piece of plumbing!

Frequently Asked Questions

Angle Grinder

Should I use an angle grinder in tight spaces? Is an angle grinder a better option than a reciprocating saw?

Angle grinders produce a lot of sparks while cutting metal, which is extremely dangerous in tight spaces where you’re probably going to be in an awkward position and really close to the tool.

Using a reciprocating saw is a better alternative, and it’ll get the job done just as fast, or maybe even faster, than the grinder. As with the grinder, you just need to equip the saw with a fine carbide-tipped blade or a high-quality diamond blade.

What can I replace the cast iron pipe with?

PVC pipes are the most common replacement for old iron pipes and a better choice for home plumbing. The main reasons are that PVC is more durable, easier on the wallet, and much lighter than cast iron, so it’s easier to work with and takes less time to install.

How do I know whether I need to replace my cast iron pipes?

The most obvious way of knowing you need to replace your old pipes is if you notice any leaking. Other reasons can be having slow drainage, noticing evidence of interior pipe corrosion, broken seams, or rust.


Now that you’ve finished reading this guide, you can confidently use an angle grinder to cut cast iron pipes with absolute ease. Following the safety precautions and the instructions we’ve provided; you can tackle this plumbing task and do it yourself safely and efficiently.

If you’ve never used an angle grinder before, you might need some practice before you can achieve the perfect cut. The key is not to force the tool, but to let it do the job for you instead.

Liam Weissman

Hello and welcome to PowerToolGenius! My name is Liam and for the last 9 years, I have worked extensively with various power tools and accessories. I have tested hundreds of different brands and models and understand the industry extensively and have been working with tools my entire life!

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