Spot Welding 101: Everything You Need to Know

Are you thinking about doing some DIY spot welding? There are a million reasons somebody may need to permanently join two pieces of metal, and spot welding may be the best way to do so.

It is especially common in the automotive industry during the original creation of the car’s body and for cheap repair options, such as a broken exhaust pipe. The welder needs to understand the specific circular points for welding and other welding basics.

What Is Spot Welding?

Spot welding is a quick welding technique to join two materials, usually metal, without affecting the other areas of the material. The strategy uses copper alloy electrodes to weld two pieces together. Through a concentrated pressure and high heat, the two pieces are melted together and fused as they cool.The pieces are typically referred to as workpieces, and they must be able to conduct electricity. Depending on the industry and need, spot welding is used for sheet metals, aluminum alloys, and even nickel straps that are used to join battery terminals.

Is it Dangerous?

Spot welding can be dangerous, particularly to welders who do not take basic safety precautions. Be sure the area to be welded is clean and easily accessible. Given the amount of heat and current, the materials need to be tightly secured.Be sure your hands and eyes are protected from the intense light of the welding torch and have all your necessary equipment gathered before you start the job.

How Does Spot Welding Work?

Spot welding works by producing conductive heat. Conductive heat is created by electrical currents. The two workpieces are held together by copper alloy electrodes. Copper is known for high heat conductivity.When the electricity flows through the copper alloy electrodes, concentrated heat melts the metal workpieces. The melted workpieces come together at the spot where the welding happens (thus the name spot welding), and fusion occurs between the two pieces.As the workpieces fuse together, the electricity is no longer needed, but the copper alloy electrodes continue to be useful by applying pressure until the pieces are fully fused.

Spot Welding Materials

Spot welding can be done with anything from sheet metal to wire mesh. Steel is probably most common workpiece because of its low heat conductivity and high resistance to electricity.Low carbon steel is the most popular choice. Stainless and alloys from titanium and nickel are also useable materials.Some materials are useable but can be frustrating to welders. Anything galvanized needs extra current to weld properly. Aluminum is also a challenging workpiece for spot welding.

How Thick Should the Material Be?

Anything workpiece over three millimeters is not ideal for spot welding. Another factor is the similarity of workpieces. Spot welding a 2mm workpiece to a 1mm workpiece is not ideal, and anything more than a 3-to-1 ration should not be spot welded.

Why Spot Weld?

Spot welding is the choice of many folks who need a fast, reliable weld. By using an electrical current running through copper alloy electrodes, there is no need for weld material. It is also useful for concentrating on a small area without having to overheat and potentially mar other areas of the workpieces.On the contrary, spot welding is shied away from when certain workpieces are not the ideal material. Others may not spot weld simply because they do not have a spot welding tool. Spot welding equipment can be expensive, and inexperienced welders may have difficulty positioning the workpieces and electrodes on oddly shaped items.Spot welding tools comprise a power supply, a capacitor bank, a switch, a welding transformer, arc welder, and the welding electrodes.

  • Power source – the supply of power during the spot welding process
  • Capacitor bank – provides the user with high power levels instantaneously
  • Switch – allows the stored energy to reach the welding transformer
  • Welding transformer – controls the voltage and current levels
  • Electrodes – join the workpieces where melting and fusion will take place

What’s the Difference between Them?

Spot welding is one type of resistance welding. Resistance welding relies on pressure and electrical current to pass through metal workpieces at the location they will be joined. It is a cost effective weld because no other materials are needed to form the bond.Spot welding, along with seam welding, projection welding, flash welding, and upset welding are all types of resistance welding. The main difference between them is the type and shape of electrodes used to apply pressure.

Seam Welding

One resistance welding process is seam welding, which uses the same resistance welding method. Instead of a shaped electrode that stays in one spot, seam welding uses wheel-shaped electrodes. The metal moves through those electrodes, which roll along the seam to create joints between the sheets of metal.Both use conductive heat created by electrical currents. Instead of using an electrode confined to one spot, seam welding uses wheel-style electrodes that that allow the metal to move over the course of a seam.

Projection Welding

Projection welding is a type of resistance welding that also uses conductive heat and resistance. Projection welding uses projections or intersections that focus heat generation at a specific point.Once the current generates sufficient heat and pressure, the projections or intersections collapse forming a weld nugget. This is the process used in cross-wire welding.

Flash Welding

Flash welding, like all resistance welding, uses heat and current to fuse workpieces together. Resistance is generated through a flashing action by using high current at a small contact point between the workpieces.Once the flashing has begun, force is applied to the workpieces, and they are pushed together and allowed to fuse.

Upset Welding

Through the use of heat and current, upset welding adds force to fuse two workpieces together. Unlike flash welding, upset welding begins with the two workpieces already touching each other so they are not moved and no flashing occurs.Pressure is already applied to create firm contact between pieces and then the current is added.

Things You Didn’t Know about Spot Welding

Welder wearing a full welding gear performing a spot welding

Image by skeeze from Pixabay

Beyond exhaust pipes, there are many practical uses for spot welding that many people never consider. For instance, spot welding can be an alternative to pop riveting.Two items that can be joined by pop rivets often could be spot welded. In industries the spot welding alternative could save time, the cost of the rivets, and form an even stronger bond.


Any construction worker or DIY warrior who has used a nail gun knows the unprecedented amount of time it can save over an old fashioned hammer. But how can time be saved assembling all of those nail gun magazines?Many companies do so with spot welding. Two copper coated wires are spot welded to each nail in a high speed, automated process. Seam welding wheels, the cousin of spot welding, are often used to increase the number of nails per minute that can be joined.


Battery manufacturing also relies on spot welding. In making batteries, different magnetic elements often have to be combined. Nickel cells are sometimes fused by spot welding.Soldering can also be used to achieve this purpose, but it is easier to manage the heat when spot welding. If the battery components get too hot it will affect the battery’s ultimate performance.


Do dentists have to know how to spot weld? Well, not really, but spot welding still plays a role in orthodontics.The metal braces you wore as a child were probably spot welded. Other molar bands also utilze the same welding process.

General Repair

Anything metal and in need of repair may be a candidate for spot welding. From the obvious example of automobiles to metal doors and equipment, fabrication shops and other repair entities consistently utilize spot welding.


Welder wearing a full welding gear id doing a spot welding

Image by Emir Krasnić from Pixabay

Hopefully this article has helped you understand spot welding better. Like all processes, it has advantages and disadvantages. If used properly and safely, spot welding can be a great tool for major industry as well as home repair buffs.Spot welding can quickly and efficiently join two pieces of metal, but the skill of the welder and the limitation of the process may not be adequate for all purposes. The current has to be applied for the correct amount of time to make the fused joint as strong as possible.It is difficult for some non-professional welders to properly place the electrode so they reach all necessary parts of the metal. The positioning of the electrodes will go a long way in determining the strength of the weld. If the current is not too weak, the heat insufficient, or the metal not held with enough force, the joint will suffer.Nonetheless, the efficiency of spot welding makes it a popular choice, and if done well, it is strong enough to hold automobiles together. And while all welding has a level of danger, spot welding requires no open flame.Shifting from man-powered spot welding to machine-powered, automated spot welding, hundreds of spot welds can be performed in just seconds.Any time two pieces of metal are joined together, it is worth at least asking whether spot welding is an option. It can save you time and money, and help you get better at a skill that can come in handy for the rest of your life.

Featured Image by skeeze from Pixabay

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