Buying guide for Best MIG Welders
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MIG welders are popular with both professionals and home mechanics, and rightly so. For a modest investment, you get a machine with a wide range of capabilities. Whether you want to fix your child's broken bicycle, make a decorative trellis for the garden, or repair a classic auto, a MIG welder is an invaluable tool. What’s more, even beginners can quickly come to grips with the ins and outs of a MIG welder.
If you'd like more detail on this topic – MIG welding basics, what to look for in the best MIG welders — read our shopping guide. If you're ready to buy, select with confidence from our top recommended picks.
How MIG welders work
A MIG (metal inert gas) welder is a kind of arc welder, and all arc welders use the same basic principle: an electrical current is passed between two electrodes, causing a short circuit across the gap between them. This short circuit, or arc, can be anywhere from 5,000° F to 40,000° F, so it melts metal very effectively.
In a MIG welder, one of these electrodes is the metal you are welding, and the other is a spool of metal wire. The wire is fed automatically by pressing the trigger on a handheld gun. The wire becomes a “puddle” of molten metal, thus creating the weld. To prevent the person doing the welding from receiving a powerful electric shock, an earth clip must be connected to a ground point.
Unfortunately, there's a basic problem with this kind of welding. Nitrogen, oxygen, and other things in the air we breathe contaminate the process. This weakens the weld. The solution is to create a “shield” around the weld area while it's being formed. There are two ways this is achieved.
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The first method uses gas — usually a mix of CO2 and argon. This is supplied from a tank and piped to the tip of the welding gun. It exits right by the welding wire and forms a protective bubble, or “shield.”
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The second method uses a metal wire with flux in the center. Strictly speaking, this is called flux-cored arc welding (FCAW), but it's generally seen as one of the two methods of MIG welding.
Somewhat confusingly, there are two types of flux wire: gas-shielded flux core wire (which still needs a gas supply as above) and self-shielded flux core wire (in which the flux burns, releasing its own protective gas). The latter is by far the more popular type; it's commonly called “gasless” in order to differentiate it from “gas.”
Many MIG welders only work with flux core wire, but the best MIG welders can accommodate both methods. So an obvious question is, which is better? Here’s a look at the pros and cons of each.
"The principle of welding with an electric arc was discovered around 1800 by Humphry Davy, perhaps better known as the inventor of the miner's safety lamp. Carbon electrodes (rods) were used at first. Metal versions were introduced soon after. Apart from the development of the gas shield and powered feed for the electrode (wire), much the same technique is used today."
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Gas welding
Pros:
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Easier to use
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Cheaper wire
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More forgiving when welding thin material
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Weld is neater and more consistent; less spatter
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Little prep needed for clean weld if painting
Cons:
Gasless welding
Pros:
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Forgiving on poorly finished surfaces
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Larger weld profile better for thick material sections
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Can be used anywhere
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No gas bottle, so more portable
Cons:
Caution
Never weld in a small, closed environment. Some ventilation is necessary to clear welding gases and fumes. Low exposure can make you feel sick or dizzy. In the long term, you risk serious damage to your health.
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A note about wire thickness
Professionals will tell you that neither gas nor gasless welding is inherently better and that you should use the wire most appropriate for the job at hand.
In practice, many home mechanics and hobbyists experiment at first but tend to prefer one and stick with it.
If you buy a MIG welder that only works with flux core wire, you may get a cheaper machine, but you don't have that opportunity.
Welding wire thickness varies to account for different metals and thicknesses. Charts are available from equipment and wire suppliers, so you can select the correct diameter for each task. It's possible to use one thickness for a wide range of jobs, and many people adopt this approach, but it's not recommended.
Did you know?
A welding mask doesn't just protect your eyes; the dark glass actually helps you see what's happening at the point of weld more clearly.
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What to look for in a MIG welder
Beyond the choice of a machine that either runs gas and flux core (gasless), or flux core (gasless) only, there are several important factors you should be aware of as a potential buyer: power output, duty cycle, torch/gun, and additional equipment/considerations.
Duty cycle
MIG welders generate vast amounts of heat and, as a result, get very hot themselves. They overheat quite quickly and need to be left to cool down before they can be used again. This operational period is called the duty cycle.
Duty cycle figures are normally given as a percentage of a 10-minute period for a given amperage. While it varies from one maker to another, here are a couple of examples.
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A MIG welder with a maximum output of 120 amps has a duty cycle of 35% at 60 amps and 10% at 105 amps. So at 105 amps, the welder will run for 10% of 10 minutes or one minute. It then needs a nine-minute cooling period to complete the 10-minute duty cycle.
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At a lower output of 60 amps, that same welder would run longer, for 35% of 10 minutes (3 1/2 minutes). The welder would then need just 6 1/2 minutes to cool down.
The conclusion is pretty straightforward: the thicker the material and the longer you want to weld, the more power you need. There is no substitute.
When shopping for a MIG welder, you'll notice that manufacturers almost never quote duty cycle at maximum amps — they tend to be quite short and don't really show the machine in the best light!
Power output
Power output impacts the thickness of material a particular MIG welder can successfully weld. Each model is rated in amps, and this relates to the maximum heat the machine is capable of producing. Although aluminum and carbon steel have very different melting points, as a general rule, the thicker the metal, the more heat (and therefore amps) you need. Consider the following examples.
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For welding a 20-gauge steel sheet, you need 50 to 60 amps.
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For welding a 1/8-inch steel section, you need 140 to 150 amps.
Most manufacturers will give you a range of maximum thicknesses. This is valuable information, but it helps to have an idea of what you're going to be welding at the outset. If most of the time you'll be working with thin steel sheets, an entry-level, 70-amp MIG welder will be fine. But if you want to weld a truck chassis, a machine with a power output that small would hardly get it warm!
You also need to look at minimum amps – because MIG welders don't start at zero. It's not such an important figure if you're welding a substantial section, but if you need to weld very thin metals, you only need small amounts of power.
Interestingly, this is an area where cheap MIG welders and low-output machines sometimes do badly. You might find that a model with a maximum of 100 amps has a minimum of 50 amps, whereas a welder with a maximum of 150 amps has a greater range and will go down to 25 amps.
There's another important thing to consider here, and that's your household or workshop supply voltage. Low-power MIG welders will run off an ordinary 110-volt socket. Larger ones will not. It varies, but above 150 amps, you may need a 220/230-volt supply.
Caution
If you're burning holes through your metal instead of welding, the power is too high.
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Torch/gun
Whether you call it a torch or a gun is a matter of personal preference. On MIG welders, “gun” is perhaps more appropriate because you squeeze a trigger to operate it.
The best guns should have an independent off switch, often called “cold contact.” The electricity supply doesn't start until you squeeze the trigger.
There are cheap models that have permanently live guns — you need to turn them off on the chassis. These are not good from a safety point of view, because if you accidentally touch the gun against a metal object, you'll strike an arc. The resultant intense spark would not only damage the item you touch, but it could also harm your eyes.
The gun activates the flow of gas and feeds the welding wire from a spool. Wire-speed control isn't actually handled by the gun, but it is an important part of its function. Some have a fixed speed, or selectable pre-sets. Variable speed is best, as it gives you absolute control.
Additional equipment and considerations
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On the MIG welder case (usually called the chassis), you really want main controls that can be operated with gloved hands. A long power cord gives you the freedom to move around. A handle makes carrying it easier. Wheels are a bonus (although one of the pros we consulted thought making a cart was a good early project).
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A ground cable is supplied. This needs a nice, strong clip so you can anchor it firmly.
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A settings guide should be provided, giving figures that tell you how to set the welder for different metals and material thicknesses.
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Overload protection is a valuable extra, protecting the circuitry of your MIG welder in case of overheating.
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If you buy a gas-capable MIG welder, a gas hose and regulator should be provided – but they aren't always. There are two kinds of regulators. One has a single gauge and tells you the pressure remaining in the bottle. The other has twin gauges and also measures flow rate. The latter is better because knowing the flow rate, rather than guessing it, will save you gas.
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Warranty length is often a good indication of the manufacturer's confidence in a piece of equipment. High-quality MIG welders can be covered for up to five years. One-year warranties are common, but we have seen them as short as six months. Be sure to check details, as different components of a MIG welder may have different warranty lengths.
Caution
Always wear welding gloves. The molten weld can spit — it is called "spatter" — and cause serious burns.
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MIG welder prices
We're usually cautious about buying low-cost machinery due to durability concerns. Often, it’s a false economy. However, if all you want to do is weld thin sheets occasionally, a cheap MIG welder will do the job. You'll pay around $100 to $150 for this sort of tool.
If you want something that will render a consistent performance on a regular basis, you'll need to invest between $300 and $400 on a MIG welder. In this price bracket, you have a great deal of choice, and actual amperage doesn't make a great deal of difference. You'll find 70-amp machines and 140-amp machines at very similar prices. It's very much a case of choosing the features you need and buying the right machine for the kind of welding you do.
When you get to machines of 150 amps or more, you're into semi-pro/pro territory and can expect to pay $800 to $1,000. What you get for your money is a robust, reliable, and highly productive tool that should last you a lifetime.
"It's perfectly possible to teach yourself to weld at home, and there are many online videos that can help. Some people prefer human tuition. If you’re so inclined, you could search local colleges for inexpensive courses."
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Tips
Good welding is all about preparation. Dirt, old paint, rust, and grease will contaminate the weld and prevent it from forming properly. This can lead to failure of the join or repair.
Use a grinder, wire brush, or emery cloth to clean surfaces, and always weld bare metal. Avoid household metal cleaners or solvents. These can leave a residue that might react badly with the flux or gas used in the welding process.
It's a good idea to practice on some scrap metal of different thicknesses while you get used to the performance of your MIG welder. Try joining edges. To create good, even welds, practice drawing lower-case letters like u and e on the surface of a piece of scrap.
A good weld has small ridges. Some professionals say it should look like a stack of dimes. Very smooth welds are weaker. The cause could be attributed to the following.
Adjust each in turn until you find the solution.
FAQ
Q. What's the difference between MIG and TIG welding?
A. Both are forms of arc welding, but they differ in technique and chemistry.
The simple answer is that MIG welding uses wire supplied on demand from a spool. It's easy to learn, fast, and efficient. It's popular with professional engineers, mechanics, and amateur enthusiasts.
TIG (tungsten inert gas) welding uses individual rods. It can produce much more precise welds, but it's slow, and it requires a higher degree of skill. It's a method for specialists.
Q. What is “arc eye?”
A. MIG welding creates an intense ultraviolet light. If your eyes are unprotected, you'll get what's called "flash burn." This is also known as "welder's flash" or "arc eye." Even very brief exposure is enough to cause temporary blindness, migraines, and extreme eye irritation that can last for days. You must always use a proper welding mask or face shield when MIG welding.
Q. What safety precautions should I take when welding?
A. As mentioned above, a proper welder's mask with a dark glass viewing window is vital. You also need to protect your hands. Welder's gloves might look a bit cumbersome, but you soon get used to them.
Most professionals also wear a welder's apron or welder's jacket and leg shields. It might appear an expensive option, but molten metal will burn through your shirt, jeans, and skin in a fraction of a second. Avoid synthetic clothing when welding. Spatter could melt it to your skin — a particularly painful type of burn.
Molten metal and sparks are a fire hazard, so make sure there are no flammable liquids around — especially if you're welding in your garage. You'll also want to keep a fire extinguisher handy. CO2 models are best because they're safe to use on electrical equipment.
