How To Break A Weld [Thermal vs Mechanical]

by WeldingWatch

If you need to break a weld you will need to use a thermal method, either a plasma cutter or an oxy-acetylene torch, or a mechanical method, such as a grinder or circular saw.

The method you use will largely depend on the type of weld you want to break and the metals involved.

Why would you break a weld?

A good weld should last a long time but there are reasons why you may want to break one.

  • Sometimes mistakes are made and if a weld hasn’t been completed correctly, it may need to be replaced.
  • Over time, welds can be come damaged and need to be repaired. If they can’t be repaired, then they’ll need to be broken and replaced.

There are different methods for breaking a weld. You can use a heat or thermal method, or a mechanical one. Whichever method you choose, cut your weld on either side, rather than try to go straight through it.

Thermal methods

When you created the weld, you used heat to melt the metals. You can also use heat to break it by using an oxy-acetylene torch or a plasma cutter.

  • Plasma cutter

Plasma cutters use a jet of hot plasma to cut through metal. Although they only have a small nozzle, they can generate heat up to 20,000 degrees Celsius and will give you a clean, precise cut every time. Once you have your plasma cutter, you don’t need any additional equipment.

While it may be easy to use a plasma cutter when you know what you are doing, you should first take the time to familiarize yourself with the speed, power and angles of attack before you work on a specific project.

Plasma cutters have several advantages when breaking a weld.

  • They are 5 x faster than manual torches
  • They can cut through thick or thin welds and a wide range of materials
  • They are easy to use
  • Plasma cutters do not use any flammable gases

Plasma cutters can be expensive, but prices are coming down so they are more affordable.

  • Torch cutter

Oxy-acetylene torches combine acetylene with oxygen to create flames of up to 3500 degrees Celsius. These flames can cut through metal, and can also weld them together. This can be more dangerous than using a plasma cutter as you are working with gas at a high temperature. You can also get electric cutters which create the same flame, but do not use gas.

If you use a gas torch, you can either gouge the metal or cut it.

  • Gouging: This involves heating the steel to approximately 900 degrees Celsius. This causes it to melt and the weld comes apart. This does take some time to get the hang of and must be done carefully, as too much heat can buckle the metal.
  • Cutting: This uses the flame to cut through the metal by heating the metal and then releasing a stream of oxygen which blows through the cut.

Torches are easy to use, once you have mastered the basics.  There are advantages to breaking a weld with a torch.

  • They are easy to use and work quickly
  • They are cheaper to buy then plasma cutters
  • They are portable so can be used anywhere
  • They work well with larger welds
  • Can also be used to weld metals together

The one thing you need to be aware of is that you will be working with gases and at a high temperature, so always consider your safety and that of others.

  • Stick welding

If you have a stick welder, then this can also be used to break a weld. You will need to buy a special nozzle to do this. Set up your welder in the usual way, and heat the metal. Once is it hot enough, the nozzle will release a stream of air which will break the weld.

If you already have a stick welder, this could be an option if you need to keep your costs down.

Mechanical methods

Mechanical methods do not use heat to break the weld. The weld is cut manually with the right equipment and usually involves cutting, grinding or drilling.

  • Grinder / circular saw

Angle grinders can also be used to grind down a weld bead or create beveled edges, but they are a good way to break a weld too. Circular saws are also a good method of breaking a weld. They will apply most of the pressure for you, so all you need to do is hold them steady and move them across the metal.

  • Grinders and circular saws are a cheap method of breaking a weld.
  • They do not use high temperatures

Grinders and saws will do the job, but they are not as precise as a plasma cutter.

  • Reciprocating saw / Hacksaw

These look like saws but are powered so they are easier to use. The blades are ideal for smaller surfaces or if you are working with a smaller or thinner weld.

  • A good choice if you are on a budget
  • Easy to use, even for beginners
  • Work very well if breaking a smaller weld

Breaking a Weld

Before you begin make sure you are wearing the right protective gear and make sure the area is prepared. If you are working with a torch or plasma cutter, make sure there is no flammable material anywhere close to where you are working.

Make sure you are wearing safety equipment which can include a visor, eye goggles, gloves and apron.

  1. First mark out where you need to make the cut to break the weld. You just need a pencil or marker to do this.
  2. Even though pieces are welded together, clamp them in place before you start. As the weld begins to come apart, they will move so it’s vital to make sure they stay exactly where you need them.
  3. If you are using a torch, turn on the gas tanks, light the torch and adjust the flow.
  4. Depending on your chosen method, move carefully across the line you have drawn, moving away from you. Don’t linger as this can cause too much metal to melt.
  5. Allow the metals to cool before you touch them. Even mechanical methods will cause the metals to heat up.

Frequently Asked Questions:

Can you weld over a piece once you’ve broken it apart?

You can, but it’s not always that simple. Some methods of breaking them apart, such as applying high temperatures, can alter the consistency of the metals, so they may not weld back to how they were originally.

Which is the best method?

There is no right or wrong way to break a weld, but you should consider the metal and type of weld you are looking to break. A strong weld will need more powerful equipment to break it effectively.

Can you break a weld with a drill?

If you’re breaking a weld, a drill will be very time consuming, it won’t create a neat cut and it could damage your drill bits. If the weld is rusty or damaged, a drill may work, but using a thermal or other mechanical method would give you a better result.


If you’re breaking a weld, you need to make sure you have practiced first and set everything up correctly, just as you would if you were carrying out a weld.

It can be tempting to ignore safety equipment, but breaking a weld will create a lot of heat and you may find slag is blown around too. For this reason, always consider where you are working and what the dangers may be.

Once the weld is broken, don’t automatically try to weld it again. Check the original metal to make sure it has not deteriorated in anyway, before attempting to re-attach it.

If you are a home DIYer, then you may already have all you need to break a weld, but even if you do not, you will be able to find a method which suits your ability and your budget.

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