If you’re new to welding, the wide range of products on the market may appear mind-blowing at first.
Like Ford, Toyota, and Mercedes Benz in the auto industry, there are several major welder manufacturers. The big boys are Lincoln, Miller, Hobart (now owned by Miller), and ESAB.
Just like automakers that turn out sedans, pickups, sports coupes, and SUVs, there are several “models” of welding machines, each serving a different purpose and catering to certain users.
Picking the right one for you doesn’t have to be hard. The information below can help guide you through the process.
Types of Welders
The most common welders in use are:
- metal inert gas (MIG)
- tungsten inert gas (TIG)
- shielded metal arc welding (“SMAW” or Stick)
- oxy-acetylene welders (“gas” or “oxyfuel”)
There are also versatile, more expensive multi-process machines that can weld with more than one welding process. Also, there are engine-driven (fuel-powered) welders for work off the electrical grid. (These more complex welders will be covered in different articles.)
For this introduction, we will focus on the basic MIG, TIG, and stick welders. If you’re unfamiliar with the different welding processes, check out the main welding processes guide before proceeding here.
An understanding of the basic processes is important for a new or aspiring welder. Your prospects for employment increase dramatically if you understand the features and benefits associated with the various types of welders.
For example, knowing which model works best for a particular assignment and what filler rod, wire, or stick electrode best meets code requirements qualifies you for work as a supervisor, project assistant, weld technician, or purchaser at your company.
This article starts with the basics of choosing a machine. After that, I will show you how to read the “specs” included in the product sales literature and teach you how to compare key features.
Step 1: Determine the Type of Metal You Will Be Welding
The majority of welds done involve carbon steel pipe or sheet metal. Carbon steel (or ordinary steel) can handle a lot of heat. So, unlike the other metals listed below, this metal is very forgiving when a novice welder applies too much heat.
Most welding processes accommodate carbon steel. Plus, you don’t need a lot of features on the machine to produce a good-looking weld.
Stainless steel (“SS”) is more finicky when it comes to dealing with heat. Composed of steel, chromium, and nickel, manufacturers use this alloy for food/beverage vessels and many other products, largely because of its anti-corrosion properties.
Workers typically weld SS using MIG or TIG machines. SS welds require less current than carbon steel to address the metal’s lower thermal conductivity.
Plus, the increased difficulty with most SS welds requires a welder with decent controls to get your arc and/or puddle right.
You can also find stainless steel stick electrodes. This allows you to use a stick welder to get the job done. But keep in mind, the base metal must be thick enough to withstand the high heat of a stick welder, and you often get more spatter compared to a MIG or TIG welder.
For welders, aluminum comes from another planet.
As a non-ferrous metal, aluminum conducts heat so well that you constantly need more of it to keep your puddle molten. At the same time, the workpiece distorts easily if it gets too hot. Consequently, aluminum frequently requires more complex equipment to get the job done.
You can use MIG welders (especially one with a pulse welding feature) on aluminum. Still, many wire-feed mechanisms struggle to feed the aluminum filler wire. So a separate add-on must be purchased, called a spool gun.
If you intend to MIG aluminum, make sure your MIG welder can accept a spool gun. Not all of them do.
A TIG welder designed for aluminum should include an AC power out option (“AC-TIG”). Other helpful features include inverter-based electronics, square wave technology, balance control, and a pulse option. Naturally, these added features will drive up a TIG welder’s cost.
Although it’s not the preferred choice, a stick welding machine can also weld aluminum. Like stainless steel, the base metal must be thick enough to withstand the high heat.
Titanium (used on custom bicycles and airplanes), Chromoly (used on motorcycles and automobiles), and other exotic metals have their own thermal sensitivity issues that welders must consider.
Because these metals are so expensive, you don’t want to be making mistakes when you weld them. Hence, they require a sophisticated TIG machine with lots of control, along with plenty of set-up and fit-up, and a seasoned veteran at the controls.
Step 2: Establish A Current Range That Covers All Possible Metal Thicknesses
The thicker the metal, the more current you need to weld a joint with good penetration.
Since the cost of a welding machine is based in part on how much juice it generates, you must determine in advance the maximum thickness of base metals and fixtures you’re going to be working on in your shop.
Thick structural steel and pipe thicker than a half-inch require the use of a heavy-duty MIG welding machine or a stick welder. According to Miller Electric, you need one amp of power for every one-hundredth inch of mild steel thickness.
For example, a 1/8″ (.125 in) sheet of mild steel requires approximately 125 amps. Stainless steel needs about 10% less juice than carbon steel, while aluminum needs about 25% more. Current settings are also tied to the diameter of filler wire/rods, as explained in our other tutorial for setting MIG machine parameters.
Conversely, working with very thin metal requires low heat (and lower amps) on a more sensitive welding machine. In this case, the objective is to provide just enough heat to get the job done.
Sometimes a low current induces an unstable arc, and that’s a welder’s nightmare. Besides that, if too much heat enters the base metal, the area surrounding the weld weakens or melts.
So, if you need to work with thin stock or aluminum, pay attention to the low end of the amps, too. Also, many of the features just described above for aluminum will also apply when welding extremely thin stock of any metal type.
If you’re careful, you can use an oxyacetylene kit to weld thin ferrous material. But make sure the torch can accommodate a tiny three-ought (i.e., 000) sized welding nozzle.
Step 3: Decide Where You Will Be Welding
Knowing where you will be welding most of the time figures into what sort of equipment you should purchase.
There are a couple of things to think about:
If you’re plugging the machine into the wall (i.e., the power grid), your choices are as follows:
- 110/120 volt AC – This is the standard power provided to every utility company customer, residential and commercial. A few entry-level arc welding machines are rated for 115 volts input power, but not many.
- 220/240 volts AC – This is the high-power, 30-amp circuit used by most welding machines. Any industrial location will have this available. Residential wiring is another matter. Since most welding equipment requires a 30-amp circuit, you may have to hire a licensed electrician to wire a circuit from the control panel.
- Single-Phase vs. Three-Phase – Most electrical equipment is designed for normal “single phase” operation, drawing from the 220-240 voltage line coming off the grid. However, at many warehouses and other industrial locations, a “three-phase” option is available. A third hot wire joins the circuit in this scenario, making more amperage available to power large motors. This option also gives you better energy efficiency, so companies are willing to invest in three-phase machines to save a bundle on their electricity bill. You cannot, however, use a three-phase machine at home.
If you’re welding outdoors and don’t have access to the power grid, you’ll need an engine-driven welder or welder-generator to complete the assignment. Farmers and welders who work in the field typically buy this type of machine.
Depending on the model, the generators run on gasoline, diesel, or liquid propane (not all three) and accommodate a stick welding torch, a Tig torch, or a MIG/Flux-core wire-feed unit and gun. The low end of this product niche starts at about $2000 and is used only for stick welding.
When reviewing product sales literature, look for the symbols CC (constant current) and CV (constant voltage) if you intend to run the welder off a generator.
CV machines are costlier but are the right choice if you’re plugging a MIG/flux-cored welder into a generator. You’ll also need to know your power requirements (i.e., maximum watts) to choose the right sized generator.
Beware, California only permits the use of generators meeting low carbon emission standards, otherwise known as CARB-compliant.
If you expect to be welding in unsheltered areas where a breeze is possible, this may negatively affect your welds.
The CO2/argon gas used with the MIG process to shield a weld’s molten puddle will get blown away and be ineffective. This problem results in oxidation and porosity in your welds.
In breezy conditions where shielding gas cannot be used, you’ll want to be able to switch a MIG machine over to the flux-cored mode (or use a straight flux-cored welder). The coated wire provides everything you need to make a good weld, including the shielding, so no gas is needed.
Alternatively, a stick welder will work in a breezy environment (but not too breezy). Like flux-cored wire in the MIG machine, a stick electrode is a flux coated to provide what you need.
Both of these welding processes contain solid deoxidizers within the wire or rod. They vaporize directly over the puddle during welding, leaving a protective layer of slag behind.
Step 4: Understanding Key Features To Compare
When reading the sales literature for different welders, the jargon and sales pitch can become hard to cut through.
But here are a few key things to look for:
This spec tells you how much uninterrupted welding a machine can knock in ten minutes.
Traditionally, the duty cycle is defined as the number of minutes out of a 10-minute period a welder can weld at the highest current the machine offers. After reaching the limit, the machine must be allowed to cool down for the remainder of the 10-minute duration.
Sometimes, manufacturers report the duty cycle as a percentage. So, you must do the math in your head. Simply multiply the percentage by ten to get the minutes you can weld per 10-minute interval. If you exceed the duty cycle, the machine heats up, and the circuits inside may fry.
For example, a very inexpensive machine with a maximum current of 70 amps may have a 10 percent duty cycle. This means you can weld for 1 minute out of every 10 without the equipment overheating or burning out.
In general, you can look for duty cycles depending on your needs. As a rule of thumb:
- light industrial/hobbyist 20%
- medium-duty 40-60%
- heavy-duty 60-80%
But nowadays, manufacturers play with the formula. To boast a higher duty cycle, they report the percentage based on a lower amperage setting. So for a machine that provides has a 10% duty cycle at a maximum of 140 amps, you might see a rating of 30% at 115 amps instead.
So, when reading the duty cycle for various welders, note the amps as well. The duty cycle goes up as the amps go down.
On the upside, you can use the same tactic to get around a low-duty cycle for a machine that otherwise fits all your needs. Just buy the model with a higher maximum current than you expect to use. That way, you effectively increase your duty cycle at the amps you need to use.
This is the voltage emanating from an arc welding torch or gun when the current is not flowing.
On the one hand, it’s sort of dangerous to have a live circuit sitting around on the workbench with the potential to cause a serious injury. (That’s why OSHA limits OCV on equipment.)
On the other hand, OCV affects how a torch electrode will perform when striking an arc. Some types of welding need the extra punch you get at start-up.
In particular, E6010 and E7018 rods in stick welding require a reasonably high OCV. That enables a crisper arc to start as the welder scratches the rod against the metal to begin the weld.
A frequent problem for students is the inability to strike an arc, so a low OCV on a small welding machine may aggravate the situation. You should take note of the OCV in the specs if you are a rookie learning how to weld.
An OCV of about 80 volts is considered normal in a stick welder. In a MIG welder, it can drop to about 35, but it’s not a big deal since, with MIG welding, the arc normally starts without fuss when you pull the trigger.
Thermal Overload Protection
Either a machine has it or doesn’t, and you should only buy a machine that has it. This feature automatically cuts output power to your torch or gun if the circuit inside starts overheating.
The fan or other cooling mechanism will continue running to help disperse the heat (assuming you leave the machine turned on).
In some specs, this feature is clearly stated. But with other products, you may need to check the equipment manual or ask a sales rep.
Step 5: Determine If You Need To Use Compressed Gases
Various gases (CO2, argon, oxygen, etc.) or mixtures of gases are used for different welding processes.
For MIG welds, the type of gas you need depends on the process, the base metal, welding position, and environmental conditions. The gases used include argon, CO2, helium, oxygen, and nitrogen, or blends of these gases. For example, a blend of argon and CO2 is common.
With oxyfuel welding, you simply need oxygen and fuel gas.
You can read more on welding gases here.
A TIG machine typically uses pure argon. But in certain special applications, it may require helium. TIG shielding gas may come as a special blend of gases designed for specific applications like MIG welding gases.
If you need to use compressed gas, you’ll want to consider a few other things:
- If you buy a welding machine that requires gas stored in a tank under pressure, at some point, you will need to transport the tank to a supplier for refills. Check to make sure there’s a supplier in your area with a reasonable policy for exchanging and filling empty tanks.
- The tanks themselves can either be purchased or leased from the supplier. Cylinders come in several sizes, so you’ll have to research what size you need based on how often you’ll be using it. As a rule, it doesn’t cost much more to fill a large tank than it does to fill a small one. Get the biggest you can afford and store.
- There are lots of safety issues and storage requirements associated with gas. Be sure you understand what’s involved before buying welding equipment that uses it. If you’re thinking of buying a used tank, be sure your gas supplier will agree to fill it before purchasing. Always keep your sales receipt and other documentation handy. OSHA requires that all tanks get inspected every two years.
- Most mild steel MIG applications call for a combination of 75 % argon and 25 % CO2, although some welders do use 100% CO2 with good results. Welding aluminum in MIG and TIG usually calls for pure argon gas. Stainless steel requires a tri-mix blend of 90% helium,7.5% Argon, and 2.5% CO2. Don’t worry; you don’t have to mix the gases yourself. You just buy the blend you need, but you will need a separate tank for each gas you use.
- While using compressed gases with an arc welding machine adds to your costs, you save money on filler rods. MIG filler wire is cheaper and more efficient than stick welder electrodes. (Self-shielding flux core wire also does not require a shielding gas.)
- Both acetylene gas and oxygen are expensive nowadays. That’s why the oxy-acetylene process is generally used for torch cutting rather than welding.
Now Find Your Welder
We’ve rounded up the top picks in each category. Find them below:
Wrapping it Up
Choosing the right welder comes down to finding what machine fits your needs. The five key points just covered will aid you in that process and include:
- Determine the types of metal you will be welding.
- Identify the thickness range you intend to work with (and the output amps needed).
- Think about where you will be working (e.g., indoors vs. outdoors).
- Compare key features of competing welders, like the duty cycle.
- Decide if you need compressed gas. If you do, make the appropriate arrangements.
These steps not only help you walk through the process of selecting a welder. You will learn about the various units and what works best in certain situations. Knowledge of the various welding processes and machines commonly used makes you a better welder and more valuable to a potential employer.