MIG Welding 101: The Ultimate Guide to MIG Welding

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Welders work in different positions and on job sites in positions that require the fusing of two or more pieces of metal. They might work for companies that restore cars and boats or in jobs with furniture companies. If you're thinking about heading back to school and becoming a welder, you need to decide what type of welding you want to do.

MIG welding is one of the more popular types of welding and is different from stick and TIG welding. Both the methods and the materials that you'll use are different too. In this ultimate guide to MIG welding, you can learn how to do this type of welding and find some tips that pros use.


What is MIG Welding?

Most beginners to the world of welding start with MIG welding, which is one of the easiest processes to learn. It requires the use of a welding gun that you use to create a pool of melted metal also called a weld pool. The electrode connects to the welder and creates the arc that transfers the substance from the weld pool to the metal.

Also called gas metal arc welding or GMAW welding because it uses a gas arch, some also call this process wire welding. As long as you can use a glue gun, you can handle a MIG welder.


How Does a MIG Welder Work?

One of the most important things that you need to understand is how a MIG welder works. You also need a good understanding of the process too. Not only do we go over how a MIG welder works, but we also look at how to use one below.

Wire

With MIG welding, you need to pick what size of wire to use first. This can depend on the welder that you use as well as your metal. Companies refer to the wires based on their diameters. Though 0.03 inches is a standard size suitable for most applications, you may want to go with a thicker or thinner wire.

Gas

MIG welders rely on some type of gas, which produces some of the energy that the machine needs. You can use a combination or standard gas in most units.

Electrode

The electrode is an important part of any welder. This is the piece of the wire that extends out from the torch. Most welders use an electrode that sticks out 3/8” from the torch.

Angle

Two terms that you need to know are the travel angle and work angle. While the travel angle refers to the angle of the welding gun in relation to a perpendicular orientation, the work angle refers to the angle of the gun to the metal. You typically use a 90-degree work angle and a travel angle of up to 15 degrees.

Turning on the Welder

Before you attempt to MIG weld, you must turn on the welder and make sure that you have everything you need. Though some welders come with digital screens and displays, others feature manual displays. This will require that you make your adjustments and check the displays to make sure everything is correct.

We highly recommend using MIG welders that come with an automatic feed for the wire spool. Instead of pausing the machine to add more wire when you need it, the machine will slowly push more wire through the torch. You can even set the welder to make the electrode stick out as far as you want.


How the Process Works

When MIG welding, you need to hold the torch or welding gun in one hand. You will place the electrode flat against a piece of scrap metal to slowly melt the wire and form your weld pool. This is the same pool that you'll return to as you create the weld.

The way the process works is easier than you might think. When you move the electrode from the weld pool to the metal that you want to weld, you'll hold it a short distance from the metal. You should see a small flash of light that represents the arc. Never press the electrode directly against the metal though as this can cause serious damage.

As long as you have a steady hand and keep moving back and forth from the weld pool to the metal, you can easily use the machine to create the strong weld that you need. It just takes a little practice.


How to Set Up a MIG Welder

You can set up a MIG welder in just a few steps, starting with the fume extractor. While you can work in a space that lacks one, the extractor will pull fumes away from your workspace. Most have a light that you can use when needed too.

Check the Adjusting Screw

The adjusting screw is the screw located on your gas cylinder/tank, which sits just below the knobs. You need to make sure that the screw is loose enough that you can twist it with one hand. This screw should reach a measurement of 10 to 15 CFH.

On the top of the tank is a handwheel that turns to open and close the tank. You will want to turn this knob to increase the flow of gas. The controls show you the PSI of the machine. A PSI of 1000 is suitable for most jobs.

Make Your Adjustments

To set up a MIG welder, you also need to make other adjustments to the machine, including setting the wire size. Most manufacturers include a chart that shows you which settings are suitable for welding different types of metal. You will need to select the wire size needed, choose your gas type and change the machine to work with the thickness of your metal.

Set Up the Welder

When you set up a MIG welder, you need to turn on the machine and change the wire speed. You can do this via the controls on the front of the welder at the same time that you adjust the voltage for the job at hand.

To use the electrode, you need to make sure that there is enough wire sticking out from the end of the torch. If the wire is too long, you can use wire clippers to cut it to the right size. The welder itself is then ready to use.


How to Set the Gas Flow on a MIG Welder

MIG welders will only run as long as there is a continuous flow of gas. Not only do you need to know how to set the gas flow, but you also need to know what type of gas to use.

Types of Gas Needed for MIG Welding

With MIG welding, you'll either use a 75/25 gas blend or 100% C02 Gas. A 75/25 blend contains 25% carbon dioxide and 75% argon. This is the best blend for most applications and is the top choice when working with any type of carbon steel. The blend will keep the electrode from burning through the metal and helps with bead welding at the same time that it reduces the splatter produced by the welder.

A 100% C02 gas is the best option for thicker pieces of metal. It reaches a higher temperature and allows you to penetrate deep into the metal to create lasting welds. The downside to this type of gas is that it doesn't work well in bead applications. C02 gas can also produce more splatter as you work.

Using a Gas Cylinder

No matter which MIG welder you buy, you can only use it with a gas cylinder. These cylinders come in various sizes, but you'll want to pick a large size to make sure you have enough gas. The most important parts of the cylinder include the adjusting screw, handwheel and measurement dials.

Adjusting the Screw and Handwheel

Once you decide what type of gas to use and connect it to the welder via a hose, you need to twist the adjusting screw to the left. If you move your hand from the side of the screw and along the metal valve, you'll find the handwheel sitting on top of the cylinder. This is what opens the flow of gas and provides a steady stream as you work.

As you turn the wheel, you want to keep your hand on just one side of it. If you place your whole hand on top of the wheel or wrap your hand around it, you risk injuries due to the high pressure inside the tank. Keeping your eye on the dial, twist the handwheel until it reaches a PSI of 1000.


Tips for Beginners to MIG Welding

Use a Welding Table

When MIG welding, you should always use a welding table. This is a table specifically designed for welding and will keep the metal from shifting. It has a completely flat top too, which helps your welds come out smooth.

You'll also want to use the ground clamp that came with the MIG welder. After placing one piece of metal on the table, decide how you want to use the second and clamp the pieces together.

Look and Listen

Two of the common signs of a problem include a crackling sound and splatter. The crackling sound can resemble popcorn popping and occurs when you use too much power. If you notice splatter, this can indicate that the wire speed is too low. Adjusting those settings can reduce the splatter and tone down the noise level of the machine.

Welding Equipment

You should never try MIG welding unless you have all the right equipment, including a welding helmet with a lifting mask and welding gloves that won't interfere with your movements. A welding apron that covers your clothing is helpful, but you should wear a long sleeve shirt and long pants made from cotton. If you weld around others, you can use a welding curtain to block off your workspace.


Learn the Basics of MIG Welding

The easiest way to learn how to MIG weld is through practice. Now is a good time to purchase a MIG welder and experiment with the scrap metal that you have around the house. You can use the steps we laid out above to adjust and set up the machine and for all the settings that you need.

Learn on the Web

If you want to pick up more tips, try watching online videos. YouTube offers hundreds of videos from professionals who will walk you through the steps of everything from choosing the right gas and setting up your machine to welding steel pieces and working with other types of metal. You'll find websites that include photos of those steps too.

Offline Learning

Another way you can learn about MIG welding is through an apprentice program. You just need to find the union(s) in your area that professional welders use. Most include information on how long the members spent welding. You can also learn about vocational training programs in your area.

These programs include classes that teach you about the popular welding methods and the machines and other equipment that you will use. You then have the chance to work in the field and put your skills in action.


Best MIG Welders

Whether you need a MIG welder that you can carry around to different job sites or use at home, you need to make sure that you buy the right one. You can pick from the following options, which we think are the best for professionals, beginners and the most affordable.

Best Overall: Hobart Handler 190

  • Best overall MIG welder for the money
  • Welds steel of up to 5/16” with one pass
  • Works at an amperage of 25 to 190
  • The speed control lets you change the speed of the wire
  • You can choose from seven different voltages
  • At a 130 amp setting, it has a 30% duty cycle
  • Includes a guide printed on the welder to make set up easier
  • Works with a separate spool gun that organizes and stores your wire
  • Weighs less than 80 pounds
  • Runs on 230 volts

Best Professional Choice: Millermatic 141

  • Best professional MIG welder and the premium choice
  • Manufactured in the United States
  • Runs on 120 volts
  • Works on stainless steel pieces up to 1/8” thick
  • Has a 20 percent duty cycle
  • Output range of 30 to 140 amps
  • Can handle wires of up to 0.035 inches in size
  • Runs for long hours without running out of power
  • Features a carrying handle and a durable frame
  • Works on aluminum, mild steel and stainless steel

Best for Beginners: Hobart Handler 140

  • Works with steel up to 1/4” in thickness
  • Can handle MIG welding applications when used with copper, iron, brass and other metals
  • Runs off the standard outlets of 120V
  • Adjustable range of 40 to 700 inches per minute
  • Can operate at up to 740 IPM without a load
  • Voltage control selector works in five different positions
  • Offers a stable, smooth and consistent arc
  • Comes with a ground clamp that also functions as a safety clamp
  • Has a duty cycle of 20% at 90 amps
  • Weighs less than 60 pounds

Best Value: Goplus MIG 130

  • Best value choice for MIG welders
  • Bright color helps you view the welders as you work
  • Durable body made from stainless steel
  • Has four adjustable welding speeds
  • Designed with portability in mind for those who work on job sites
  • Includes a brush that functions as a clipping hammer and welding wire
  • Comes with a mask that you can wear with a welding helmet
  • Two vents on the side of the welder reduce the internal temperature
  • Built-in safety features protect against surges and thermal problems
  • Control panel lets you adjust all functions

Final Thoughts

Professionals often recommend that those interested in welding start with the MIG process because it's so easy to learn. All you need is the right gear and a welder. You can purchase one for beginners and upgrade to a better model once you learn the fundamentals. We recommend a few good choices in our section on the best welders.

MIG welding uses an electrode that produces an arc, which lets you transfer metal from a liquid pool to a piece of metal to connect to the second piece of metal. With our guide, you can easily learn the basics of this process.