plasma cutter cutting welds

If you have been welding for some time you would know that it is the process of fusing metals to one, usually with the help of electricity. Welding is used to creating complex structures and frameworks of metals in almost every industry. However, laying beads is not the only skill you need to have to finish projects successfully. Most of the times you also need to know how to undo a weld if you mess up. From small household projects to bigger and complex ones, welding can do the job. It is just amazing how creative you can be is you know how to weld.

However, much like anything, there are different types of welding processes used. Your requirements determine which type of welder you should use.   

As welding creates a strong bond between two metals, this bond is usually stronger than the metals themselves. If you are just starting out, there is a high chance that you make mistakes while working on your first projects, and to correct the mistakes, in most cases, you need to know how to undo a weld.

There are several ways you can use to undo the joints. But each is better done alongside rather than applying directly on the weld. The reversal process also depends on the type of weld you want to undo. Depending on the type, you can apply either a mechanical reversal or thermal reversal.

Types of cutting a weld open

Let us look at these types in a little detail and then move towards the steps involved.

Thermal methods

Just as the name suggests, you have to use high heat in order to reverse the process of welding. This can be done by using an oxy-acetylene torch or a plasma cutter.

  1. Plasma cutting


With plasma arc cutting, with the help of direct current, an arc is created which temperature can reach up to 40000 degrees. The heat is generated thanks to the high pressured airflow directed out from the small nozzle.

  • Torch cutting


This method is a little more dangerous in my opinion, for novices at least. Typically this torch uses a mixture of oxygen and acetylene. The gases are mixed with the help of a cutting torch, creating a flame hot enough to be capable of cutting through very thick pieces of steel. To put it simply, all you have to do is mark the line where you want to perform the cut, ignite the torch, fine-tune the arch and follow the line slowly with the torch until you cut all the way through the metal.

Mechanical weld reversal

In mechanical processes, you have to perform the cut manually. There are a few actions you can perform depending on the type of weld you are dealing with. Spot welded sheets are difficult to separate and oftentimes you have to perform the separation process through drilling into the sheets. Sometimes it is impossible to separate the metals without damaging the base metals. Mechanical processes mostly involve drilling, grinding and cutting.

Breaking apart the weld without the use of a grinder


If you want to break apart a weld without the use of a grinder, you can use drilling as a mechanical process or plasma and torch as a thermal reversal process. Of course, in some cases, you can use a band saw or even a hacksaw.

Steps involved

Let us see the steps involved in undoing a weld. Remember, Safety first!

  1. Mark the metal where you want to make the cut. You can do this using a pencil or a marker.
  2. You have to secure the metal pieces in place, so they don’t move. This is done using clamps or a vice.
  3. If you are using a gas torch, you need to open the gas tank. If you are using a plasma cutter, you should connect the power cord and turn on the torch and turn on the compressor and make sure it is connected to the machine. After this, you should adjust the flame of the torch.
  4. Move the torch/saw/Dremel along the line that you marked with a pencil or a marker. You should do this slowly and steadily. There is no rush. But be sure not to linger too much on the same spot. Continue to do this until you have made a successful cut.
  5. The last step is to shut off the preferred tool and allow the metals to cool down before handling them.

Cutting a weld using a grinder or a circular saw

This is a type of a mechanical reversal. There are several steps involved in this process. They are discussed below.

Steps involved

  1. Mark the place you want to make the cut using a pencil or a marker.
  2. Secure the piece you want to cut in a place using clamps.
  3. Put on your protective gear
  4. Connect the grinder or the saw, whichever you are using to make the cut, with an electric outlet.
  5. Slowly allow the grinder to start cutting through the metal. There is no need to push the grinder with force to the base metals, you should let it do the work. If you push the grinder too hard, you run into a problem of breaking the cutting discs and it is very dangerous.
  6. Cut off the power and allow the metal to cool down. The heat is due to friction.

You can also perform a mechanical reversal of a weld using either a saw or a hacksaw. However, this requires great physical shape which I don’t have and it usually leaves me tired and strained.

Which process is better for you?

In order to decide which process suits you the best for undoing a weld, you need to determine the type of base metal. As mentioned above, welds are strong and if you want to undo the thin sheets joint together, you have to drill or grind off the bead to crack it open.

Welding often times leaves either one of the pieces damaged. This is because of the use of the filler metal, but it can easily be fixed if you have a grinder or a nice metal file. A lot of times after you cut the weld, you need to grind off the bead to weld the pieces again. Grinding off the excess metal helps to lay better bead second time, as opposed trying to weld the metals without removing the excess metal.

Conclusion:

Welding is an amazing process, but we all make mistakes and luckily bad welds can be fixed. In order to fix it, you need to undo the weld. As I mentioned above, there are quite a few methods to do the job, but my preferred method would be an angle grinder or a plasma cutter. Nothing can beat angle grinder if you are working on smaller projects in my opinion. Although it might not give you the same results that you would expect from a perfect weld made with the first attempt, these techniques are still better than throwing away the whole project. This is especially nerve-racking if you are almost done with your project.