How To Fix Cast Iron Without Welding

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We find cast iron in many industries and even as part of several home structures and items such as a cast iron pan. But because of the brittle nature of the cast iron, it is prone to cracking and ultimately breaking if not well maintained.

These cracks develop as we use them due to very sharp temperature changes. You can repair a cracked or broken piece of cast iron, so it is not a useless item. One common way is to weld the pieces together.

Cast iron welding, if done well, can be very durable. But then welding cast iron is a complex process that requires expert training in using a welding rod which is why many people consider how to fix cast iron without welding. There are several methods you can apply in fixing your cast iron or wrought iron without welding it. These include cold metal stitching, using epoxy putty, and brazing. This article walks you through how to repair cast iron without welding using these three methods.

Cold Metal stitching

Like its name, the cold metal stitching involves lacing up pieces of metal that have been cracked using another metal. You would be able to stitch up cracked cast iron materials on construction sites or in heavy industries.

Since you are not using heat, there is no stress imposed on the other material parts. Cold metal stitching is also popular because it saves the stress of disassembling and reassembling the cracked cast iron piece.

How To Fix A Cast Iron Using Cold Metal Stitching

  • First, assess the extent of the crack: You should easily repair cracks from 3/16 inches to up to a foot wide. For cracks that are wider or in thicker materials, you might consider other methods we would discuss 
  • Drilling the needed holes: If you have concluded on using cold metal stitching, the next step would be to make holes to place the stitch. These holes are made perpendicular to the crack at specific intervals. Depending on how large the fissure is, you could make several such holes along the gap.
  • Connecting the holes: Using a chisel, join the rows of holes together. At this point, you would want to be careful about the size of the chisel you are using and how you join them, so you do not create slots. Well-formed holes allow the keys to sit well once they have been inserted.
  • Insert the keys once all is ready: Begin placing the keys into the holes you have already created. Ensure the keys are about the same length as the holes you have already made this way; they fit tightly and create sturdy work. You might use a mallet to get the keys to fit. However, do not get too bothered if some materials are still left outside.
  • Fixing screws between the stitches: The keys you have installed are good, but they might break under intense heat. To avoid this, make sure to sew or fix screws between the metal keys. The tighter this stitching, the stronger the fix would be.
  • Finishing: You might have leftover metal sticking up from the previous step, so the next step is to create a neat finish. Using a chisel, or a grinder, remove the excess material and sand down to a fine finish. For a neater work, you could add other finishes to the original work.

Using Epoxy Putty

Epoxy putty is a quick fix for cracked and broken cast iron items. This works well for cast iron at home and can be readily done. Although this method is relatively easy, it is also essential to maintain safety by wearing a dust mask and work gloves. 

Epoxy putty is a quick fix for cracked and broken cast iron items.

How To Fix A Cast Iron Piece Using Epoxy Putty

  • Purchasing the tube of epoxy putty. You can easily find it at a local hardware store. Depending on the type, they come in two tubes; the hardener and the resin. A popular epoxy choice is the JB weld.
  • Using sandpaper, sand the cast iron to remove dust, paint, or any dirt that might be clinging to it. Asides from removing the dust, creating a rough surface allows the glue to bond strongly. For this step, you must move in a way that would not cause the crack to widen.
  • Once the dust is removed, using soap, water, and a rag, thoroughly wash off any particle from the grinding or dust. Completely dry the cast iron after washing before you proceed.
  • Stir and squeeze out the epoxy on a flat surface such as cardboard and mix using a putty knife. Usually, there would be an instructional guide you would follow in mixing and stirring the epoxy. 
  • Using the putty knife, apply the putty to the crack. Ensure that the damage is covered completely. If there is excess, scrape that off using the putty knife before it dries and gets difficult to remove. Once the putty is applied, you would have to wait about 24 hours for it to dry before handling your cast iron.
  • The finishing, in this case, may require applying paint over the sealed space or repainting the whole cast iron as you wish. Otherwise, you could leave it. Painting is recommended as the final step not just because of its aesthetics but also to enhance durability.

Brazing For Cracked Cast Iron

A minimal amount of heat is applied to the material in the brazing method to heal the crack. Cracks in cast iron often result from intense heat and pressure on the item. The heat in this process is significantly reduced, unlike welding. 

In welding, the cracked cast iron pieces are melted and joined together; however, when brazing iron pieces, the work metal is not melted. The filler metal is melted and flows into the joint or the crack and cools. 

How To Fix Cast Iron Using The Brazing Method

  • Selecting the filler metal: many fabricators use filler bars made from nickel or brass. Ensure that the metal you are choosing is of considerable strength.
  • Sandpaper and Grinding: As with all cast iron mendings, ensure that the surface of the crack is thoroughly cleaned using sandpaper to remove layers of oxides and impurities. 

With a clean surface, use a grinder to create a cross-section where the filler bar would sit. Creating this space allows the melt to flow into the crack easily. Remove any particles and dust from the grinding using a steel brush.

  • Heating the Cast Iron: Because the cast iron can be affected by a sudden intense heat, it is best to heat the whole piece over a grill, an oven, or a burner. Areas around the crack should then be specifically heated using a brazing torch.
  • Inserting the filler metal: with concentrated heat around the crack, you can place the filler rod into the fracture. One recommendation is to keep the temperature, especially around the damage, very hot using a brazing torch so the filler metal could flow in easily. 
  • Cooling the work: after the crack has been filled with the filler, cover it entirely with sand to cool for at least a day. Cast iron is very brittle, so you should cool the repaired portion slowly to avoid breaking it. Therefore exposing it to air cooling causes it to cool rather rapidly, causing it to crack again.

In Summary

Welding, although suitable, can result in more damage if not done well. Other ways to fix a damaged cast iron apart from weldings include using epoxy putty, brazing, or cold metal stitching. You must use the best method for the cast iron piece you are working on, as using the wrong approach can cause more damage. Do not forget to prepare the surface to be worked on for an effective fix.

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