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Tips and tricks for safe and productive welding, and the care of MIG welding machines.

What Size Welding Gas Cylinder for MIG or TIG? Argon|CO2

If you’re new to MIG or TIG welding, you may have no idea how much welding you’ll do—let alone how much welding gas you’ll go through.

But you’d probably like to have some sense of how long a welding gas bottle will last before deciding what size cylinder to choose.

I’ll show you how much welding time to expect from the most popular cylinder sizes used by hobbyists. Then you can compare physical dimensions so the bottle will fit your vehicle or welding cart. 

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What is a Tweco® Style MIG Gun?

How many innovative product designs can you name that have lasted half of a century?

In 1969, Tweco Products, Inc. (formerly Townsend Welding Equipment Company) introduced a new MIG assembly design. Tweco’s invention used a single cable to transfer gas, welding wire, and electrical power to the MIG gun. The MIG gun was also a new lightweight, cool-operating design.

Most MIG guns mounted on today’s modern MIG welders follow the fifty-year-old Tweco design. And, many product descriptions include the phrase “Tweco Style” when referring to MIG torches or consumables. Many buyers are left wondering: What is a Tweco Style MIG gun?

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MIG Welding with 100% Argon Shielding Gas

Welders are problem solvers.

We can agree that running out of MIG gas in the middle of a project is a problem.

Since we also tend to experiment, you may have asked yourself if the gas kept on hand for TIG, or MIG welding aluminum could be pressed into service. Would MIG welding with 100% Argon on mild steel let you finish your project without a trip to the local (or not so local) gas supplier?

Or, is it possible to get by with one bottle of 100% Argon welding gas for all your MIG and TIG work?

As a hobby welder, I keep one bottle of C25 gas and another of 100% Argon for aluminum MIG work. It’s impossible to judge how long the gas will last.

So when the MIG bottle gets low, I get leary of starting a new project. Should I invest in another bottle of C25 or trade in the not-completely-empty one for a fresh bottle?

Never happy with these options, I’ve also wondered if worse comes to worst could I MIG weld with 100% Argon?

Can I use 100% Argon to MIG weld steel?

Yes, 100% Argon can be used to MIG weld steel, but you’re likely to get an unattractive weld bead that is tall and narrow, often with a weld-weakening undercut.

Mild steel MIG welds using 100% Argon shielding gas are also known for losing ductility. So on top of being weak, the welds can be brittle.

Illustration comparing MIG weld bead profile of 100% Argon to a MIG mix.
Illustration comparing MIG weld bead profile of 100% Argon to a MIG mix. (WelditU)

100% Argon doesn’t provide enough thermal conductivity for a fluid weld pool when MIG welding on ferrous metals. The outer edges of the arc remain cool, resulting in a deep but narrow penetration profile, and minimal fusion.

And with more spatter and an erratic arc, to go along with a stiff weld puddle, this is not a welding setup you would enjoy using on a regular basis. For full-time use, 100% Argon is not a suitable replacement for MIG-mixed shielding gas.

OK in a pinch

I don’t hesitate to use 100% Argon on MIG welds—as long as it’s a project that’s not going to hurt someone or cause me a lot of trouble if a weld fails.

There’s plenty of talk on the forums from those who have had success MIG welding with pure Argon shielding gas, and they offer a few tips:

  • It’s natural to want to turn up the heat when you see the high, narrow, cold-looking welds. But with the narrow penetration profile of Argon, you’re likely to burn through thin materials before the bead flattens out.
  • Beveling your joints can help achieve better fusion for stronger welds.

Ductility is the capability of a metal to be permanently bent, twisted, or otherwise manipulated without breaking or cracking.”

Tusla Welding School

What can you MIG weld using 100% Argon gas?

The use of straight Argon in aluminum welding is familiar to many hobby welders. But its purity and low moisture content, also makes 100% Argon a suitable shielding gas for MIG welding other non-ferrous metals:

  • Copper under ⅛” (including alloys)
  • Nickel under ⅛” (including alloys)
  • Magnesium
  • Titanium

Helium, with its higher thermal conductivity (and cost), is often blended with Argon for use with thicker non-ferrous materials.

Photo showing a MIG welder and cylinder of C25 shielding gas

Why blend CO2 with Argon in MIG mixes?

At low temperatures, CO2 is an inert gas. At welding temperatures, CO2 becomes reactive and cleaning action improves. When added to Argon welding gas in small amounts, usually 5 to 25%, CO2 helps to stabilize the welding arc. With an Argon/CO2 MIG mix, you’ll get a more fluid weld pool with improved penetration, along with reduced weld spatter.

At higher levels of CO2, the arc becomes rough, and the amount of spatter starts to increase. The strong penetration characteristic becomes harder to control when welding on thin metal.

You’ll find Argon/CO2 blends labeled according to the percentage of CO2 gas in the mix. So a C25 mixture is 25% CO2 and 75% Argon.

Why TIG welding with 100% Argon is more effective on steel

Shielding gases have different jobs in different processes. In MIG welding, where the consumable filler material forms the electrode, the metal transfers across the arc to the weld. While with TIG welding, the filler metal feeds into an arc established between the material and the tungsten electrode.

TIG welding benefits from a shielding gas that remains 100% inert at welding temperatures, and pure Argon fits the bill. When used in TIG welding, Argon promotes easy starting, stable arcs, and keeps the non-consumable tungsten electrode clean.

Watch a welding instructor MIG welding with straight Argon shielding gas:

Is there any doubt how Bob feels about Argon welds?

Of course, he’s a professional responsible for teaching and maintaining the highest of welding standards. But he also has the experience and resources to make that happen.

Me? Sure, sometimes I want pretty welds (I’d like more of my welds to look like the ones Bob described as “Blah!”). But more often, I need to be effective and complete the job using the resources I have on hand.

Under the right conditions, a hobbyist welder can use straight Argon to make effective MIG welds.

Whatever project materials we use, we are always ultimately responsible for choosing fastening methods suitable for the intended use of the finished project. This is true whether using screws, staples, adhesives or welding.

The bottom line

The next time you’re caught short on MIG gas, go ahead and feel free to experiment—try MIG welding with 100% Argon.

You may be able to finish your project without a trip to the supplier.

Just know that results will vary. Use sound judgment and test your work so that no one gets hurt.

Speaking of saving a trip, did you know that Amazon delivers FULL bottles of C25 and 100% Argon to your door at a great price?

What Shade Lens for MIG Welding? The Easy Way to Be Safe

Hands-down, my auto-darkening helmet is my favorite piece of welding safety equipment. I appreciate technology that not only makes a product safer but more comfortable and enjoyable to use.

Adjustable auto-darkening welding helmets protect your eyes from radiation and bright welding arcs with lens coatings and electronic shades from DIN 3 to a super dark DIN 14.

A light shade setting of number 3 or 4 provides enough visibility to position your MIG gun without having to lift your mask, but what shade lens for MIG welding?

What shade lens for MIG welding?

“As a rule of thumb, start with a shade that is too dark to see the weld zone. Then, go to a lighter shade which gives a sufficient view of the weld zone without going below the minimum.”

OSHA Fact Sheet No. 3499

Recommended Filter Lenses for Protection during Gas Metal Arc Welding (GMAW) and Flux Cored Arc Welding (FCAW)

Arc Current

OSHA Shade Number Minimum

ANSI & AWS Shade Number*

UNDER 60A

7

60-160A

10

11

160-250A

10

12

250-500A

10

14

According to OSHA’s Fact Sheet, MIG welding (GMAW) or flux-cored welding (FCAW) using currents of 60 to 500 amps requires a minimum lens shade level of a DIN number 10.

Both ANSI and AWS are more cautious, recommending a shade number 11 for welding at 60-160 amps, a number 12 for 160-250 amps, and a number 14 for 250-500 amps.

Welding helmet lens shade ANSI Z87.1 certification.
Verify that both the welding helmet and lens shade meet ANSI Z87.1 certification.

You may not know that most welding helmets with auto-darkening filters (ADF) provide full, or close to full, protection from eye-damaging ultraviolet (UV) and infrared (IR) radiation at all times, even while in the passive light state.

I found this in my helmet manual:

Auto-darkening shade lens technical specifications
Source: www.northerntool.com

…and this from another helmet manufacturer:

“Has permanent protection (Shade 12 equivalent) against harmful UV- and IR- radiation, regardless of whether the filter is in the light or dark state or whether the auto-darkening function is operational.”   

—3M Speedglas 100 Datasheet

Instead of relying on dark state shade settings to block eye-damaging radiation, auto-darkening helmet manufacturers use special lens coatings to filter out the rays.

So, if the helmet battery dies, you leave the mask in grind mode (so easy to do!), or the ADF fails to darken for any reason, the lens still protects your eyes from damaging UV or IR rays.

You may experience temporary spots in your vision from the brightness, but you won’t suffer permanent eye damage or painful conjunctivitis known as “welders’ eye” or “arc flash.”

To protect your eyes, look for helmets meeting ANSI Z87.1 standards and review the manufacturer’s technical data sheets for a helmet’s permanent shade protection level.

Auto-darkening welding lens shade adjustment control.

What does the welding lens shade number mean?

The DIN rating is a German industrial standard used to classify light filtering levels. As the DIN number increases, the lenses become darker and block more light.

Most auto-darkening lenses have a passive base level of DIN 3 or 4. This light state is bright enough so you can see to set up your work without having to lift your hood.

And it allows you to see well enough to operate your grinder—provided your helmet has a grind mode to prevent grinding sparks from triggering the darkened state.

A DIN shade 3 level allows around 14% of visible light through the lens, while DIN 4 is three times darker, allowing only 5% light transmission. A significant difference that you should consider if you don’t always work in a brightly-lit area.

My helmet has a base shade of DIN 3.5 (10%). As a hobbyist welder most often working in the corner of my garage, I think anything darker would be too dark for my comfortable use.

By comparison, blocking the brighter-than-the-sun welding arc, shade 9 allows just 0.037% light transmission and shade 13 only 0.00072% (blocking 99.99928% of light!).

Here’s a brief video showing what you can see in the light state compared to the darkened mode:

How to adjust your auto-darkening shade lens?

If you use an ADF helmet having a permanent shade rating higher than the capacity of your welder—meaning the lens coatings will block all the UV and IR your welder generates—you’re free to choose a setting based on your comfort.

An ideal setting is just light enough so you can see what you need to see but dark enough to prevent eye fatigue. If you see spots in your vision after a weld, it’s time to choose a darker shade setting.

My personal preference runs closer to the darker shade settings in the ANSI and AWS recommendations. The reason is likely my light-colored eyes. As everyone is different, your actual setting will depend on your working environment and personal preferences for comfort and visibility.

Welding helmet lens shade test button.
Welding helmet lens shade test button.

How to test your auto-darkening shade lens

Many better auto-darkening welding shade elements have a self-test button to show you that the ADF in your helmet is working. But remember, this test only determines that there is battery power and the ADF can work, it doesn’t prove that it will work when you strike an arc.

There is another quick and easy method to test your lens operation, including the sensors, for troubleshooting purposes or your piece of mind. The helmet sensors trigger off IR from the welding arc. An ordinary television remote control emits an IR signal that will also trigger the helmet’s sensors.

This handy trick can also test how well the sensors pick up signals from side-to-side, or above and below your mask. Good information to know when working around other welders.

What are symptoms of “Arc Eye”?

“Certain types of UV radiation can produce an injury to the surface and mucous membrane (conjunctiva) of the eye called “arc eye,” “welders’ eye” or “arc flash.” These names are common names for “conjunctivitis” – an inflammation of the mucous membrane of the front of the eye. The symptoms include:

  • pain – ranging from a mild feeling of pressure in the eyes to intense pain in severe instances 
  • tearing and reddening of the eye and membranes around the eye (bloodshot)
  • sensation of “sand in the eye”
  • abnormal sensitivity to light
  • inability to look at light sources (photophobia) 

The amount of time required to cause these effects depends on several factors such as the intensity of the radiation, the distance from the welding arc, the angle at which the radiation enters the eye, and type of eye protection that the welder or bystander is using. However, exposure to just a few seconds of intense UV light can cause arc eye. These symptoms may not be felt until several hours after exposure.”

Canadian Centre for Occupational Health & Safety
Northern Tool Model 19056 auto-darkening welding helmet.
Northern Tool Model 19056 auto-darkening welding helmet.

Need a good, reliable helmet for hobby MIG welding?

I still use my first auto-darkening helmet bought from Northern Tool in 2010. Before the Klutch branding of Northern’s welding gear, it’s a Northern Industrial Welding Model 19056. I think it was $60 at the time.

I consider this one of the best welding purchases I’ve made. As a MIG welding beginner, upgrading from a no-frills, fixed-shade mask to a much more convenient to use auto-darkening helmet was a real treat for me. I felt safer, more comfortable, and much more able to focus on learning to weld.

Northern now calls this helmet the Klutch 700 Series Auto-Darkening Welding Helmet with Grind Mode. It sells for $80 but goes on sale for $60.

What I like about my helmet:

  • Easy to use and reliable
  • Solar and AAA battery powered (original batteries lasted seven years).
  • Light-weight (under a pound) and comfortable to wear—easy to forget I’m wearing it.
  • Room to wear safety glasses under the mask for even more protection.
  • Grind mode so sparks won’t darken the shade.
  • Reasonable price

There is one problem I have with my helmet

I often use my helmet’s grind function. But the switch is located inside the helmet, making it difficult to operate without removing the mask or taking off a glove.

If I were to replace this helmet, I’d look for one with an external grind mode switch—like on this helmet—that I could operate wearing gloves without disturbing other nearby settings.

Before you go

Sure, welding as a hobby has some risks. There’s live electricity, red-hot pieces of metal—sometimes flying through the air towards your face—and brighter-than-the-sun arcs. What could go wrong?

But in truth, we have excellent welding safety features, procedures, and personal protective equipment available to reduce risks so we can safely enjoy our hobby.

A must-have for the hobbyist welder, an affordable auto-darkening welding helmet provides excellent eye protection and peace of mind.

The technology in our helmets lets us safely choose a comfortable darkness level without worry about what shade lens to use for MIG welding.

How to MIG Weld Aluminum Without a Spool Gun

You’ve heard the horror stories about MIG welding aluminum without a spool gun—but you’re still thinking of giving it a try.

I get it. Spool guns are expensive and have drawbacks.

Sure, aluminum welding is tricky even if you’re using a $250 spool gun. But if you’re up for the challenge—and have a little patience—I’ll show you techniques and tips to use your welder to MIG weld aluminum without a spool gun.

And you’ll see how one of the most popular 120-volt hobby welding machine does on aluminum straight out of the boxwithout a spool gun.

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