What Is Spot Welding And How To Do It? | Application, Materials & Tools Guide

Of all the welding processes, spot welding is by far one of the oldest and most commonly used. But what is spot welding, really?

The spot welding method, simply put, is the process by which two metal workpieces are joined together through a combination of heat and applied pressure (from electrodes) without the addition of filler metal materials. That is, the weld comes about by joining the two pieces by melting a part of them, using their own molten material for the weld. The result is a strong, durable weld with a uniform appearance.

What Is Spot Welding?

Using a spot welder for your welding needs is often a good alternative to even the best TIG welders. This is because spot welding requires much less effort, skill, and expertise than TIG welding. But it’s not just that spot welding requires less know-how that makes it a great option. It’s also very cost-effective, as there is no need for filler metal and the equipment required is rather minimal

tig welders are often used for spot welding

Spot welding, as we’ll cover in more detail later, is an effective welding method for joining two or more overlapping pieces of steel. While we won’t go into the full step-by-step procedures for spot welding in this guide, we will cover the various uses and general methods and ideas behind its processes.

Resistance Spot Welding

In fact, learning how to spot weld is one of the easiest things to do in the world of welding. While the learning curve for the top-rated MIG welders is also fairly small, the limited amount of materials, equipment, and general know-how required for resistance spot welding makes it an even better option for beginning welders.

So, if you’re a true novice when it comes to welding, you might give spot welding a try first. The initial, upfront costs are often less than other alternatives, and it is much easier to learn.

A further advantage to using spot welding is the nice, uniform results you can get when done properly. While there’s no such thing as a fool-proof welding method, spot welding comes fairly close. Since it requires less skill and effort, there is less room for error, which will likely result in perfectly uniform welds for your sheet metal components. Even better, while these spot welds certainly look attractive, they also produce strong, durable results.

How Does Spot Welding Work?

Spot welding (or, more accurately, resistance spot welding) is, as the name implies, a method of welding in which two metal components—most often metal sheets—are welded together by a series of “spots” at regular intervals. Rather than welding the joint along the entirety of the metal components, the welds occur at these spots, spaced out along the components at equal distances apart. This is the “spot” part of the name.

As for the “resistance” aspect of the name, this is due to the pressure involved to join the two components together. Once a molten core (known as the “nugget”) is created by melting the adjacent parts of the metal components, the applied pressure creates the weld between the two. After you turn off the electrical current, this “nugget” hardens to form the joint.

how to do spot welding

The heat and pressure required for this type of weld comes from the two electrodes placed on either side of the adjacent metal workpieces. The electrodes are most often comprised of a copper alloy for its conductivity. These copper electrodes shoot an electric current back and forth between the workpieces, creating an adequate amount of heat for sufficient melting of the interiors of the two metal workpieces.

Materials Appropriate for Spot Welding

Spot welding is an effective welding method for a variety of different materials; however, there are some materials that are more suitable for this process than others. The following list outlines the most commonly used materials for the spot welding method:

  • Steel
  • Stainless steels
  • Aluminum (though certain precautions need to be taken to accommodate its lower resistance)
  • Copper

Where Is Spot Welding Used?

While there are plenty of useful applications for a spot welding machine and the spot welding method, when it comes to its use in industry, it is most often used to assemble the sheet steel components of automotive bodies. This is because spot welding is very effective at creating joints between metal components of 3 mm thickness or less. This is also why it is important that the thickness of the metal workpieces to be joined should be roughly the same thickness, but the ratio of their thicknesses could vary up to 3:1.

where is spot welding used

Spot welding machines are also very useful for other types of sheet metal projects. This might include cabinets or brackets that involve sheet metal components that must overlap.

Unlike high-quality arc welders, portable spot welding allows you to perform welding processes in a variety of environments and workspaces. The fact that a spot welding gun is not necessary makes the process highly portable and requires very few parts and equipment for a successful weld.

What Electrode Material Should I Use for Spot Welding?

electrodes are the primary pieces of equipment used in spot welding

Since the electrodes are the primary pieces of equipment used in resistant spot welding, determining the proper material for them is of utmost importance. In fact, our best spot welder tips have to do with this very topic.

As we mentioned above, these electrodes are most often comprised of a copper alloy; however, the type and amount of additional metals added to the copper alloy provide different results for different types of projects and welds.

For instance, Class 2 materials (like a copper-chromium-zirconium alloy) are the most frequently used. These are most appropriate for stronger steels with low carbon content.

On the other hand, more highly conductive copper alloys, like copper-zirconium, may be more suited to welding coated steel. These more conductive electrodes don’t add as much heating to the surface of your materials.

However, if you are using even harder base metals, like stainless steel, it is important to use electrodes with higher forces and weaker electrical currents. Class 3 electrodes, like copper-nickel-silicone, are going to be your best options.

There are, of course, many other options for a variety of different welding purposes, but the aforementioned ones should be a good start for you.

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About the Author Gregory

Hi, my name is Gregory! I have been welding practically all of my life and love it. As I have gotten older I have started to weld less and less, so in order to continue my love for welding I created this website. I like to write about my experiences and help you all become welders. I hope that you enjoy the site!

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