Skip to content

How to Drill a Hole in Cast Iron: Steps and Tips for Drilling Into This Tough Metal

How to Drill a Hole in Cast Iron

When you’re DIYing your home or apartment, it doesn’t take long to get frustrated with the limitations of the materials you’re working with. Cast iron is one of those materials that seems like it shouldn’t be that difficult to work with – until you try drilling a hole in it. It’s an incredibly dense metal and drills will snap on impact before they even begin to cut into the surface.

When faced with this kind of challenge, you need to think outside the box… and come up with some creative ways to get around the limitations of your tools.

Thankfully, there are a few ways that will make drilling holes in cast iron much easier than you might expect. Keep reading for our tricks for getting around these tough metals.

Use Drill Bits Made of Corded Brass

Corded brasses are one of the oldest, most inexpensive metals. A drill bit made of corded brass will have a much lower melting point than steel, and will likely be more flexible than other types of materials, meaning it can bend and flex in response to the stress of the drill bit breaking through the surface. Make sure you buy a high-quality corded brass drill bit, though, as cheaper versions will crumble, rather than forming a point, and be useless for this application.

You can find a wide range of sizes and styles for these types of drill bits at any home improvement store. If you’re working with a very thick cast iron pan, for example, you’ll want a thicker drill bit, as well. Corded brass is also much cheaper than other options, so it’s great for anyone who is on a tight budget or is doing a lot of DIY projects.

Add a Fluid to Help the Drill Bit Rotate

If you’re working with a cast iron that’s very thick, you may need a more powerful drill than a corded brass drill bit can provide. In this case, you can add a fluid to assist the drill bit’s rotation and help it break through the surface faster.

There are a few different types of fluids that can work here, but we’d recommend using synthetic oil. Cast iron tends to have very high mineral content, and adding oil to the surface of the cast iron will help the drill bit to navigate through the mineral content more easily.

You can also use a water and soap mix, but oil is best for this application because it will evaporate, leaving the cast iron surface intact. Make sure you choose an oil that’s designed for high-heat applications. Dow Corning 220 is a good option. Also, oil and water, about 20% oil and 80% water is the recommended mix.

Read more: Detailed Dewalt DCF885C1 Review

Use a Hammer Drill

If you’re using a corded brass drill bit and synthetic oil, and the cast iron is very thick, you may have a tough time getting the drill bit to cut through the surface. In this case, it’s best to switch to a hammer drill, which is designed for tougher applications, like drilling into concrete.

A hammer drill can take the stress off of the drill bit and help it cut through the surface much more easily. Just make sure you don’t use oil with a hammer drill, as it will gum up the drill bit, and you’ll have to clean it out frequently.

We’d recommend using water or drywall mud.

Use an Electronic Tool

If you’re still having a difficult time breaking through the cast iron with your corded brass drill bit, synthetic oil, and hammer drill, it’s time to get serious. In this situation, we’d recommend using an electric rotary tool as opposed to a hammer drill. It’s easy to get aggressive with a hammer drill and end up with a broken drill bit, but an electric rotary tool can spin slowly, helping you to be more precise with your drilling. Make sure you have a high-quality, durable bit intended for cast iron, as these types of tools can be very powerful and easily break the wrong types of drill bits.

Cast iron is a tough material, but it can be drilled. The best thing you can do to make the drilling go smoothly is to make sure you have the right tools for the job. There are many types of drill bits made from different materials designed for drilling into different types of metals.

We’d recommend a corded brass drill bit for thinner cast iron or a hammer drill for thicker cast iron. You can also add fluid to the drilling process to help the drill bit cut through the mineral content in cast iron. An electric rotary tool can also make the drilling process much easier. Make sure you follow these tips and you’ll be drilling into cast iron in no time.