How to Repair Cast Iron – 3 Easy Methods

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Cast iron typically finds its uses in various industrial and household structures.

Objects made from cast iron are durable and can be used for decades when maintained well. However, you can accidentally cause it to fall or it can develop cracks due to wear and tear.

No matter what the damage, if you are looking at how to repair cast iron, you have come to the right place. In this article, you will learn the top effective methods to fix cracks or join broken pieces of a cast-iron object.

how to repair cast iron

How to Repair Cast Iron

Method 1: Epoxy putty

The first and easiest method doesn’t involve expertise with any tools. It’s fixing the cracks or broken pieces using two-part epoxy resin. The best thing about epoxy is that it’s not only a great adhesive, it also fills gaps and fixes uneven surfaces.

There are other types of adhesives such as superglue and polyurethane glue that are easier to administer. However, epoxy glue is the best of the lot. It is more durable and acts as a long-term fix, especially for metal objects.

If you are repairing something that will be exposed to heat, make sure the two-part epoxy you select is heat resistant.

Mixing the Epoxy

Two-part epoxy comes in separate parts — the resin and the hardener. You must follow the instructions on the packaging. It should say how much glue is to be dispensed so that you do not use too much or too little.

Dispense the required amounts from both tubes onto a piece of board. You can mix them together with a putty knife so that they combine well.

Applying the Epoxy

This mixture has to be applied on the crack and over it on the cast iron. You have to wait at least 24 hours and let it dry before you can use the object again. You may paint the repaired area to match the rest of the object if you wish to.

Before you apply the epoxy glue, it is recommended that you clean and sand the cast iron object. This is so that there is no dust and other particles on the surface when you apply the glue.

So, if you are wondering how to repair cast iron the easy way, the epoxy glue method is preferred by most DIY enthusiasts. It does not involve the hassle of dealing with fire and complicated tools.

Adhesives do not make the object bulky unlike cold stitching — where metallic bolts and screws make the object heavier than it’s supposed to be.

They are also corrosion-resistant. It’s an overall quicker and more durable alternative to other methods such as welding, soldering, and riveting.

That said, there are occasions when adhesives may not be an option. For example, when you have broken cast iron pieces from a vehicle’s engine spare part, which tend to be quite heavy. In such cases, you could go for brazing or cold stitching.

Method 2: Brazing

The next popular method is called brazing. This does not require as much heat as welding does, but also does the job of putting together broken case iron pieces quite well.

It does need some practice but once you get past the initial learning curve, you would find that this method is very effective.

Brazing typically involves joining metal pieces by melting or flowing what we call a “filler rod” into the joint, thus combining multiple pieces into one single object. It does involve some effort and technique, however, it is very effective and durable.

Brazing the Cast Iron

Remember to always use appropriate safety glasses and safety gloves when brazing.

Step 1: The very first step is to select the filler rod. This is the piece that will be directed into the crack in the cast iron or joint. It will act as the combining agent between the pieces. Usually, the filler rods are made from brass or nickel.

Step 2: Next you must prepare the cast iron object for the brazing process. It’s a good idea to sand it to ensure a smooth surface to guarantee the creation of a strong bond.

Once you grind or sand the rough edges, clean the surface to get rid of any particulates or dirt. These could disrupt the brazing process.

Step 3: Slowly heat the cast iron part. Clamp the object on a work desk if needed. Hold the brazing torch near the surface of the crack or joint and burn it until it turns a hot red. Now touch the filler rod to the surface of the crack or joint.

You would have heated the surface enough for it to melt the filler material and cause it to flow into the crack or joint. Hold the torch near the surface to maintain the temperature so that the filler rod can flow evenly down the crack and fill it.

Now your broken pieces are combined. If you are dealing with a cracked object, the crack is now filled with brass material. The filler material would most likely have a color that’s very distinct from the cast iron.

If that bothers you, you can look for options to paint it to match the rest of the object.

Cooling the Cast Iron

Place the fixed cast iron object in a container filled with sand. You can also cover it fully over the top with sand in order for it to cool down slowly.

If a part is exposed to a sudden dip in temperature, it can cause the object to crack. Cool it down slowly by using the sand container method. You can leave it for a day or longer than that depending on the size of the cast iron object.

Method 3: Cold Stitching

Cold stitching is a method that actually uses metal keys (or stitches) to hold the cracked parts of a cast-iron object to bind them together.

Repairing cracks in a cast-iron object using the cold stitching method first involves drilling holes on the object alongside the crack, joining the holes together using a large chisel, inserting the metal keys into lengths of the holes so that they create a bond, and sewing them together to hold them in place using screws.

You can learn more about cold stitching here.

Cold stitching makes the object a little bulkier overall with all the metal keys and screws. However, this method ensures that the broken pieces or cracks are fixed tight. It does not involve a brazing torch, making it a less risky alternative. You can consider cold stitching if you are wondering how to repair cast iron.

There you go! These are some effective methods to repair broken pieces of your cast iron objects. Try them right away.

FAQs on How to Repair Cast Iron

How do you repair a hole in a cast iron skillet?

You can use a cast iron filling compound or the two-part epoxy resin to fill the hole in a cast iron skillet.

Can a cast iron skillet be repaired?

Yes, a cast iron skillet can be repaired. Depending on the damage it has encountered, you must choose a suitable method to repair it. Almost always, a good way to repair it is to use epoxy putty. In other cases, if possible you can fix it using a brazing torch or by using the cold stitching method.

Takeaway

If you are wondering how to repair cast iron, you have a few options. The easiest and the most hassle-free option is to use the two-part epoxy resin to combine broken pieces or fill a crack.

However, if the object is too bulky for an adhesive you can either use the cold stitching method where you are essentially fixing the crack by combining it with metal keys and screws or if you are up for the challenge, you can use a brazing torch to melt a filler rod and get it to flow into the cracks of a broken cast iron piece in order to repair it.

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