What is a Plug Weld?

Last Updated on May 17, 2022

Being aware of the different kinds of welding is essential for one to become an expert welder. Having said this, one of the most fundamental (and simple) types of welding that a welder must know is called the plug weld (AKA Rosette weld).

Understanding what this weld is and knowing when and how to do it is especially important for those headed toward the automotive manufacturing industry because of how crucial it is.

So, whether you’re a welder looking to enhance your skill set, a welder headed for the automotive industry, or just someone keen on learning about welding, this article is for you. Please stick with us as we cover the basics of Plug (or Rosette) welds in the following sections.

Understanding plug welds

Plug Welds (sometimes called Rosette Welds) refer to a process in which 2 pieces of metal are joined together using welds placed in tiny circular holes (similar to a plug). Typically, this procedure is performed on 2 pieces of overlapping metals, where the metal towards the top hosts the holes where the weld is deposited.

Those familiar with spot welding would appreciate the value of Rosette Welds. This is because they are an excellent alternative when spot welds are impossible. Several occasions arise when welders, particularly amateurs and small enterprises, cannot find the equipment for spot welding.

Additionally, they may discover that they cannot correctly place their spot welder equipment due to odd angles or size constraints. Plug welds come to the rescue during this time, and when performed correctly, plug welds can even be stronger than spot welds.

How to perform a plug weld

Here is the process of placing a plug weld simplified down into 5 easy steps. This is to give you a sense of what the process looks like, so don’t make the mistake of thinking that this is all there is to plug welding.

  1. Start by setting up your equipment and preparing yourself for the weld. Do this by cleaning up the metals thoroughly to avoid any issues during welding and ensure that your welding and safety gear are ready to go.
  2. The next step is to precisely mark where your weld will come on the metal. If you are making several plug welds, they must be uniformly spaced.
  3. With reference to your markings on the metal (see the previous step), begin drilling holes for the plug welds. This may be accomplished in a variety of methods, although welders often use a drill for this.
  4. Once the holes have been drilled, hold the two metals with each other to prevent them from moving around during welding. The best way this is achieved is with the help of plug welding clamps.
  5. The last step is to place the weld. The key point to bear in mind is to begin from the outside (around the edges) and slowly move towards the center. This enables the metal’s base to reach the same temperature as the metal- enhancing the weld’s strength and diminishing the possibility of a fault.

Plug weld symbol & its meaning

Now that we have taken a good look at what plug welds are and why they’re necessary, it is time to move our discussion towards the symbol that denotes a plug weld and how to interpret it. Here is an illustration of what a plug weld’s symbol looks like. If you’re on your path to becoming a learned welder, you will do to memorize it.

Here is an illustration of what a plug weld’s symbol looks like. If you’re on your path to becoming a learned welder, you will do to memorize it. In the figure, you should see a diameter sign beside a number on the left side of the symbol, which denotes the diameter of the pipe. Due to this reason, this part is referred to as the diameter symbol.

At times, you will find yourself dealing with plug welds that don’t require a filled hole. During such times, your reference should become the number that lies in the symbol’s center. This figure will tell you how deep the hole is.

Lastly, you must always be ready for the possibility of several welds being applicable at the same time. You will find a bracket beneath the symbol which tells the welder the number of welds that need to be applied. In addition to this, the numerical figure towards the right of this symbol will tell you the measure of the distance between each weld.

Differentiating between a plug weld and a slot weld

Now that we have a fair understanding of plug welds, let’s solidify our concepts about them by differentiating plug welds from slot welds – a commonly associated term.

Plug and slot welds both serve the purpose of joining metals, with one hosting the holes for the weld (the holes are usually circular for plug welds but stretched out (elongated) for slot welds). To create this connection, welded metal is put inside the holes, which fuses together with the base of the metal that belongs to the two welding components.

Through an extended hole, a slot weld connects the surface of one metal surface to the other. The hole may be partly or filled to the brim with welding elements.

Both of these welds serve the purpose of transferring shear force. That said, there are times when they are employed to transfer shear in lap joints, unite parts of constructed members, and prevent lapped portions from buckling.

Plug welds (AKA Rosette Welds) refer to the process where two metal pieces are joined by welds being placed into circular, plug-like holes – typically performed on two pieces of overlapping metals where the top metal has the holes for welding deposits.

The process of performing plug welds can be covered in 5 easy steps, which are:

  1. Prepare your equipment and clean the metal to avoid welding problems.
  2. Use a marker to mark the holes where the holes will be drilled uniformly.
  3. With reference to your markings, drill holes for welding.
  4. Use a plug welding clamp to fasten the two metals together.
  5. Place the weld and start from the outside before gradually moving towards the center.

Lastly, spot welds are commonly associated with plug welds, so it is important for you to know the difference between these two terms – which is that the shape of a plug weld is defined using diameter measurements, while slot welds are defined using the measurements for diameter as well as length.