How to Use a MIG Welder?

Using a MIG welder typically requires setting the voltage, wire feed speed, and gas flow rate. These settings are based on the type and thickness of the material you are working with. 

MIG welding is a popular welding technique for hobbyists and beginners. It’s more forgiving compared to TIG welding. Here is what you should know before using a MIG welder.

When to Use a MIG Welder

Metal inert gas (MIG) welding is typically used to weld thick materials but can also be used on thinner materials. It’s a versatile welding method suited for a wide range of applications.

MIG welding is used throughout the welding industry and the industrial sector. It’s suited for working on plumbing, vehicles, ships, pressurized vessels, and more. 

You can also use MIG welders to fuse sheet metal, making it popular for hobbyists. MIG welding is easier to learn and more cost-effective compared to other welding techniques. 

MIG welding also works best in a controlled, indoor environment. It’s not the best option for welding outdoors, such as when working on agricultural buildings. 

Here are my recommendations of the best MIG welders for beginners:

Editor’s ChoiceBest OverallBest Value for MoneyBest on a Budget
ProductLincoln Electric MIG 180Hobart MIG WelderForney MIG Welder
Previewlincoln electric mig 180hobart mig welderforney mig welder
FeaturesHigher voltage and Amps can weld up to 1/2 thick metal.MIG and Flux Core, 5 position voltage control, 10 ft cable lengthFlux core only, no gas required, suitable for DIY
More InfoCheck Latest PriceCheck Latest PriceCheck Latest Price

How to Set Up a MIG Welder

Here are the main considerations when setting up a MIG welder:

  • Material thickness
  • Wire thickness
  • Voltage
  • Wire feed speed
  • Gas flow rate

The typical MIG welder includes two main settings – the wire feed speed and the voltage. These settings depend on the material and filler wire. 

Material Thickness

You need to consider the type and thickness of the metal when selecting the MIG welder machine settings. The thickness of the metal determines the amperage of the MIG welder.

The typical guideline calls for 1 amp of power per .001 inch of thickness. 

For example, a ¼-inch (0.25 inches) metal bar may require 250 amps. Metal measuring 1/8 inch (0.125 inches) may require 125 amps.

Yet, different types of materials may require more or less output. Stainless steel requires about 10% to 15% less output while aluminum requires up to 25% more.

Wire Thickness

Here are the general recommendations for amperage based on wire size:

  • 0.023-inch wire: 30 to 130 amps
  • 0.030-inch wire: 40 to 145 amps
  • 0.035-inch wire: 50 to 180 amps
  • 0.045-inch wire: 75 to 250 amps

Most MIG welders come with 0.030-inch wire. It’s suitable for working on sheet metal with a thickness of about 1/8-inch. 

Voltage

The voltage of the MIG welder controls the arc length. The arc length is the distance between the weld pool and the wire filler. 

A higher voltage causes the weld bead to flatten. A lower voltage raises the height of the bead. It essentially controls the heat.

Choosing the right voltage depends on the material’s thickness, the wire’s thickness, and the type of gas. Luckily, almost all MIG welders have a chart or manual for calculating the right voltage.

Lincoln Electric MIG Welding Amperage Table

Wire Feed Speed

The wire feed speed refers to how quickly the machine feeds the filler wire. As with the voltage, the wire feed speed is typically listed on the chart or manual that comes with your MIG welder.

If you already know the amperage, you can estimate the wire feed speed in inches per minute (ipm) using the following formulas:

  • 0.023-inch wire: 3.5 x amps 
  • 0.030-inch wire: 2 x amps 
  • 0.035-inch wire: 1.6 x amps 
  • 0.045-inch wire: 1 x amps 

For example, you’re using a 0.030-inch wire with a 120-amp machine. You’d likely use a wire feed speed of approximately 240 inches per minute (2 x 120 amps = 240).

Gas Flow Rate

The gas flow rate for MIG welding can range from 10 cubic feet per hour (CFH) to 65 CFH. The flow rate is often set based on the size of the nozzle on the welding gun.

A slow gas flow rate limits the effectiveness of the shielding gas. Setting the flow rate too fast wastes gas.

The ideal gas flow rate for a ½-inch nozzle is typically 18 to 22 CFH. The recommended gas flow rate for a ¼-inch nozzle is about 10 to 14 CFH. 

Components of a MIG Welder

The basic components of a MIG welder include the following:

  • Power supply
  • Welding gun
  • Shielding gas
  • Filler wire

The typical MIG welder includes all the components needed to start welding, other than protective gear for yourself

Power Supply

MIG welding machines mostly use direct current (DC) power sources. The power source is typically a heavy-duty transformer. It’s the MIG welder’s main component, as it sends power through the electric arc. 

Some of the smallest MIG welders produce up to 60 amps. Larger machines produce up to 400 amps. The typical hobbyist only needs about 140 amps. This allows you to work with material up to about a 1/8-inch thick.

Welding Gun

The welding gun, or torch, acts as a guide for the wire-fed electrode. It also contains a trigger. The trigger initiates the electric arc and the welding process. 

The average welding machine includes an air-cooled gun. The shielding gas cools air-cooled welding guns as it passes through the nozzle. 

Water-cooled guns use water to cool the nozzle and are typically found on welding machines used for commercial purposes. A water-cooled nozzle is needed for welding with higher currents. 

Shielding Gas

Welders have used shielding gasses for about 100 years. Shielding gasses protect the metal from oxidation and contamination. 

Inert gasses are colorless, odorless, and non-chemically reactive. These gasses essentially create a shield around your work area. 

Filler Wire

The filler wire acts as an electrode. It conducts electricity, which allows for the formation of an arc. An arc forms between the filler wire and the workpiece. 

It’s possible to use a MIG welder with a flux-cored wire filler metal. However, the flux core filler creates a lot more toxic fumes. 

The flux also creates a layer of slag as it burns. You can remove the slag after you finish the weld.

Do I Have the Right Gas for MIG Welding?

Gas is almost always used with MIG welding to shield the work area. Shielding gas protects against oxygen and other elements interfering with the weld.

Using a shielding gas produces fewer fumes and is easier to use. The four most common choices include:

  • Oxygen
  • Carbon dioxide
  • Argon
  • Helium

Keep in mind that you may end up using a combination of gasses. For example, a 75/25 argon/carbon dioxide combination is a common choice when using a MIG welder. 

Oxygen

Oxygen is considered a reactive gas. It’s used in smaller ratios compared to the other gasses, as it causes oxidation. 

Oxidation increases the porosity of the weld, limiting its strength. It’s not recommended for use with aluminum, copper, and magnesium due to the risk of oxidation. 

Oxygen is typically only used in combination with other gasses, such as argon. For example, you may add 2% to 3% oxygen to argon to improve its arc stability compared to using 100% pure argon. 

Carbon Dioxide (CO2)

Carbon dioxide is another reactive gas. It’s the least expensive gas and the only reactive gas that doesn’t require an inert gas. 

You can use 100% pure CO2 when welding steel. It offers deeper penetration. It also creates a less stable electric arc and greater spatter. 

Argon

Argon is one of the most popular gasses for MIG welding. Unlike the previous two gasses, it’s not reactive. It helps reduce spatter compared to using pure CO2.

100% pure argon is recommended when working with non-ferrous metals, such as aluminum and titanium. It also has lower thermal conductivity and it’s non-combustible.

100% pure argon isn’t recommended for welding steel. The outer edges of the electric arc remain cold when using argon, limiting penetration. This makes it less ideal for thicker materials. 

If you’re working with ferrous metals, consider using a mixture of argon and CO2, such as 75% argon to 25% CO2

Helium

Helium is another gas used for non-ferrous metals. It’s also a common choice for stainless steel due to its ability to promote deep penetration.

Helium tends to work best with thick materials. It creates a hotter electric arc compared to other shielding gasses, which allows you to increase the travel speed of the filler wire. 

Helium is also cheaper compared to argon. A common combination involves using 10% argon, 85% helium, and 5% CO2. This tri-mix blend can save money compared to using a mixture with a higher ratio of argon. 

Do I Have the Right Welding Rod for MIG Welding?

The welding rod, or wire, is available in various thicknesses to suit different applications. Common sizes include:

  • 0.024 inches
  • 0.030 inches
  • 0.035 inches
  • 0.045 inches

The 0.030-inch wire is used for material up to 1/8-inch thick. However, if you’re working with 24 gauge (0.025-inch) or thinner material, you may want to use 0.024-inch wire. 

A 0.035-inch wire is recommended for material measuring between 1/8-inch and ¼-inch thick. A 0.045-inch wire is recommended for material measuring ¼-inch or thicker. 

You also need to decide between the solid wire and the flux-cored wire. Solid wire is often recommended when working with thinner metals. Flux-cored wire produces more splatter.

Yet, flux-cored wire is also useful for certain situations, such as welding outdoors. The flux-cored wire doesn’t require shielding gas to protect against oxygenation.

The flux-cored wire can also help you create a perfect weld on rusted workpieces. The flux can deal with rust and impurities better. 

How to Prepare the Metal for MIG Welding

Remove any oil or grease from the material that you want to weld. Contaminants can impact the quality of the weld.

Use a rag and a degreaser to eliminate grease. Use a sanding disk or abrasive cleaner to remove any paint, rust, or scale from the metal. 

Rinse the metal to remove residue from the previous cleaning steps. Finish with an alcohol rinse. Alcohol removes any remaining debris and evaporates quickly.

You need to secure the metal after cleaning it. Use clamps, magnets, or pins to secure the two pieces you want to fuse. 

How to Position the Welding Gun

After preparing the metal, turn on the welding machine and position the welding gun. The gun should typically sit at a slight angle away from the direction you work.

If you’re right-handed, you’ll likely move from right to left. This gives you a better view of the weld pool. The gun should be angled about 15 degrees to the right. If you’re left-handed, angle it about 15 degrees to the left. 

If you’re creating a butt joint, work from a 90-degree angle. The welding gun should be perpendicular to the joint. If the joint includes a 90-degree bend, position the welding gun at a 45-degree angle. 

How to Evaluate Your Weld Quality

You can evaluate the quality of the weld by looking at the consistency of the bead. A high-quality weld should have a smooth seam with a flat bead penetrating the base material.

Setting the voltage or wire feed speed incorrectly can limit the quality of your weld. 

If the voltage is too high, the bead flattens, resulting in less penetration. If the voltage is too low, you may notice a spatter and a convex profile on the bead. 

A fast wire feed speed limits penetration and creates less consistency. A slow wire feed speed also limits penetration and causes burn-through.

Burn-through occurs when you completely burn through the base material, resulting in an open hole. These holes limit the strength of the joint and the base material. 

mig welding

Conclusion

Using a MIG welder isn’t the most complex task. You first need to prepare the metal that you plan to weld. Clean the metal and secure it in place.

Select the right filler wire based on the thickness of the materials that you’re working with. A 0.030-inch wire is the most common choice. The material and wire help you select the MIG welder’s amperage, voltage, and wire feed speed. 

If you’re new to welding, test a small area of the metal you want to weld before attempting to create long, straight passes. Evaluate the quality of your weld and adjust the MIG welder settings accordingly.