How to MIG Weld

Miller Portable Welder Units are One of the Best At-Home MIG Welders for Hot Rodders

By Ron Covell   –   Photography By the Author

The principles of welding are easy to understand: the parts to be welded are heated to their melting temperature, then caused to flow together—often with the addition of some filler material. As simple as this sounds, there is some knowledge and skill required to make a weld that is strong and good looking.

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Welding is a transformative skill for anyone who works on vintage vehicles. It enables you to accomplish so many tasks that require permanently joining metal components, and it’s a skill that most people can learn with some practice.

02 learn to weld MIG better quality welders use a shielding gas for better welds with minimal splatter
The better-quality MIG welders use a shielding gas to keep the atmosphere away from the weld puddle. This makes it easier to get strong, good-looking welds with minimal spatter.

Welding technology is always evolving; the newest machines are small, light, and easy to set up. If you want to learn to weld, there has never been a better time. Oxyacetylene and stick welding have been around for ages, and they still have their place, but in the world of car builders, TIG and MIG welding lead the pack. We’ll focus on MIG welding in this article, and cover TIG soon.

MIG is the most popular type of welding worldwide. The equipment is affordable and easy to set up, and the process is relatively easy to learn. MIG welding works well for nearly any automotive application—from the thin metal used for bodywork to the heavier material used for chassis modification and repair.

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03 learn to weld MIG flow proper gas rate
It’s essential to flow the proper amount of gas for each welding setup. Typical values are between 15 and 20 cubic feet per hour.

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 All MIG welder machines have controls for the voltage and for the (filler) wire feed speed. These parameters need to be set based on the diameter of the filler wire and for the different types and thickness of metal to be welded. Most machines have a chart that recommends a good starting point based on the specifics of your particular job. Some machines, like the Miller Electric unit pictured, have a simplified control panel allowing you to simply dial in the wire diameter and the material thickness and the settings are made automatically.

The beauty of the MIG welding process is that the gun feeds the filler wire automatically, usually shielding it with a gas. The gun is equipped with a trigger and in the off position all the functions are inactive. As soon as the trigger is pulled the welding current is energized, the shielding gas starts flowing, and the filler wire is automatically fed into the joint to be welded. This is so easy that it can be done with one hand, although most welders use both hands on the gun to achieve better control.

04 learn to weld MIG clean metal provides a better ground connection
It is very important to have a solid electrical connection to the work. It’s best to put the clamp directly on the part being welded and to clean the metal where the clamp attaches.

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So, you may ask, if this is so easy, why does it take time and practice to become a good welder? Like so many things in life, the devil is in the details. There is a lot involved with holding and moving the gun, and you need some understanding of the various factors at play as you are welding.

Let’s start with one of the most basic considerations: how close you hold the gun to the work. For most automotive work, the gap between the tip of the gun and the metal being welded should be around 3/8 inch. If you get much closer, you are very likely to cause the hot end of the filler wire to fuse to the contact tip inside the gun nozzle, which will instantly stop the weld and most likely damage the contact tip.

05 learn to weld MIG Miller welder chart inside machine with settings
All MIG welders have controls to set the “Voltage” and the “Wire Feed Speed.” Most machines have a chart to show the recommended settings.

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Holding the gun too far away from the work reduces the coverage of the shielding gas and it lowers the heat going into the weld. Both can degrade the weld’s penetration and mechanical properties.

The gun distance is often referred to as “stickout,” referring to the length of the filler wire that bridges the gap between the contact tip inside the gun nozzle and the metal being welded. Again, 3/8 inch is a good place to start, but as you develop your own style you will find what works best for you.

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06 learn to weld MIG Miller Electric welder automatically adjusts voltage based on thickness of metal
Some machines, like this Miller Electric welder, can set the parameters automatically, based on the metal type, thickness, and the wire diameter you’re using.

The angle between the gun and the work is very important, too. For a butt weld, the gun should be held at 90 degrees from the work when viewed from the end of the joint. In most cases you should angle the gun about 5 to 15 degrees in the direction of movement. For example, if you are right handed you would start the weld at the right end of the joint, angle the nose of the gun slightly toward your left, and move the gun to the left as the weld is made.

It takes some time to master the best gun angles and the proper travel speed to get a nicely formed weld bead with good penetration. It’s best practice to use both hands on the gun, which gives you better control and makes it easier to maintain the ideal stickout. The smoother and more consistent you are with your movements, the better your welds will be. MR

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07 learn to weld MIG Ron Covell uses two hands to steady gun
Whenever possible, it’s best to use two hands on the gun. This helps to steady the gun movement, resulting in a more uniform weld.
08 learn to weld MIG angle and distance from metal are crucial
The angle of the gun and the distance it’s held from the metal being welded are crucial for making a good weld. For most welding, the tip should be around 3/8 inch from the metal.
09 learn to weld MIG 5 to 15 degrees away from vertical and direction of travel
The “travel angle” is the angle the gun should be held away from vertical. The recommended angle is 5 to 15 degrees with the nozzle pointed in the direction of travel.
10 learn to weld MIG butt joint with gun at 90 degrees
For a butt weld, the gun should be held 90 degrees from the metal, as seen from the end of the joint.
11 learn to weld MIG fillet joint centered between pieces with torch at 45 degrees
For a fillet weld, the gun should be centered between the plates. For a 90-degree joint, the torch angle would be 45 degrees.
12 learn to weld MIG lap joint gun at 45 degree angle
For a lap joint, the gun angle should be close to 45 degrees, although you can modify this if necessary.
13 learn to weld MIG lap joint favor the thicker material
When making a lap joint with unequal material thickness, it may be beneficial to angle the gun more toward the thicker piece, or to hold the gun slightly away from the center of the joint, “favoring” the thicker part.
14 learn to weld MIG tack weld butt joint first then finish weld
You should always tack weld a joint before finish welding. The spacing between tacks should be 1 inch or less.
15 learn to weld MIG edges of bead blend smoothly
You can tell a lot about a weld by looking at the profile of the bead. The edges of the bead should blend smoothly into the base metal, like this example.
16 learn to weld square tubing in four steps
When welding rectangular tubing it’s best to do it in four steps, finding the most comfortable position for reaching each of the four faces.
17 learn to weld fillet joint sheet metal
A fillet weld on sheet metal requires good gun control and the proper settings to avoid blowing holes through the metal.
18 learn to weld clip ball of wire off for better arc
A small globule will form on the end of the filler wire after each weld. You will get more consistent arc starts if you clip this ball off before starting each weld.
19 learn to weld Miller aluminum MIG gun
Some MIG welders can be equipped with a special spool gun that allows them to weld aluminum.
20 learn how to weld MIG aluminum
Being able to weld aluminum opens a new world for car builders.


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