(How To Choose?) .030 vs .035 Flux Core Wire

As a new or novice welder, it’s tricky to know which size to go for.

In the battle between .030 vs .035 flux core wire.

Even the most experienced welders’ debate this.

And argue which is the best flux core wire size to use.

You’ll find here three stories to help you decide.

And if you stay to the end.

You’ll get points to bear in mind before you buy.

.30 vs .35 Flux Core Wire?

Sometimes for speed. You’ll hear .030 and .035 welding wire casually referred to as .30 or .35 flux core wires.

And think the .0 in the name isn’t important.

But it is.

Why?

It describes the size of your flux cored wire.

What’s The Difference Between .030 And .035 Welding Wire?

.030 and .035 are size labels.

And describe the diameter of your flux core wire.

The impact?

Literally .005 of an inch.

That’s not much. I hear you say.

But .005 gap is key to your successful welding.

To show you the difference between .030 vs .035 welding wire flux core.

And when you’d choose one over.

Listen to the story of these three welders.

*Disclosure: This document contains affiliate links. And at no extra cost to you this site earns a commission through these links should you decide to buy.

Your 4 Best Flux Core Wires For Mild Steel

Click through the text links above to check the latest price on Amazon.

And click on the link text in the next sentence. To find an article on this site with the reasons why these 4 flux core wires are the best.

Joe’s Story

Joe, has never welded before but he really wants to learn. Let’s see where he’s at.

Joe: “Hi, I’ve some stuff that needs fixing up around the yard. And in the past, I’ve paid for a guy in town to weld up a few things for me.”

Joe ran his hand through is wavy hair.

“I had around 100 dollars spare so I bought myself a MIG 130 to get going. I don’t have much money for this new hobby of mine.”

Joe rubbed the stubble on his chin.

“The Super Deal is flux core. I thought that would be straightforward enough for me to start with. I need some flux core welding wire and I’m not sure which to get? It can take 1lb. or 2lb. spools of either .030 or .035 flux cored wire.”

What is your flux core welder capable of Joe? What Amp range?

“Between 50 to 120 Amp, though the duty cycle talks about 105 Amp for one minute”

What will you be welding?

“All sorts I guess.” said Joe. “The Super deal can weld from 18 gauge up to 3/16ths and I’d like to have a bit of a go at quite a few jobs around the yard.”

I’m guessing as you’ll be welding all kinds of stuff. Some of it will be a bit rusty, not all lovely straight edges, maybe a bit gappy.

Joe said. “Yep, that’s about right. I saw some Blue Demon flux core wire at a reasonable price.”

Ok, let’s look at the spec sheet for that wire and compare it to what your welding machine can do. That’ll tell us what the deal is.

The Blue Demon #2, E71TGS is .030 size, single pass flux core. That means that you’re not going to be able to weld quarter inch steel. Because that’ll need multiple passes to build up the weld.

The #2 means that it’s a 2lb. spool. So that’s good. It’ll fit in your little flux core welder.  You should always check what size spools your welder can take.

It’s rated for use in all positions. That means welding on the flat, vertical, welding overhead.      Though I would think to start you’ll be mainly doing flat horizontal welds. But it’s good to know you should be fine for vertical welds when you build up to that.

Now to the important bit. Let’s find and download the Blue Demon welding parameters chart.

Blue Demon E71TGS	.030	​.035
Welding Range (Amp)	50 – 175	75, 100, 150, 200
Voltage Range (Volts)	15 – 17	​15 – 18
Wire Feed Range (Inches Per Minute)	80 – 445	70 – 305

“What’s one of those.” Joe said.

The wire parameters chart tells us what the wire’s capable of. You’ll find the welding parameters for all the sizes you can buy the wire in. The Blue Demon welding range is 50 – 175 Amp on their .030 flux core welding wire.

A nice wide range. And it’ll suit your welder as it can weld from 50 Amp to 120 Amp.

You’ll find it’s best for now. Till you get more experience. To stick to the 105 Amp they talk about as the Super Deal duty cycle. Think of it as a max for your welding.

The voltage range on the wire is 15 to 17.  You’re using standard household power?

Joe nodded.

I strongly suggest you put any welding machine using household power on its own 20 Amp circuit. Both the .030 and the .035 flux core wire is inside the voltage range of what you’ve at home to power your Super Deal..

The wire feed range on the Blue Demon flux core is 80 to 445. With your little welder you’re going to have to play around to find the right speed settings.

Because the welder’s paperwork doesn’t declare the wire feed speed range.

“What about the 035 wire?” Asked Joe.

I was just getting to that. The welding range for the .035 is 75 Amp to 200 Amp and I note that the wire jumps quickly up from 75 to 100 Amp.  

You’re going to have your welder set at least half way up its Amp range to even start an arc with the 0.035 wire. And you’ll have a much reduced duty cycle.

Joe said. “Why is that?”

The larger your wire size. The more power you’ll need to melt it.

And then the higher you set your flux core welder. The shorter your welder’s duty cycle.

Recommended wire feed speed range for the .035 Blue Demon wire is from 70 to 305. Now we’re not sure what kind of wire feed speed you’re getting on your welder. But this tells me that you’ll want to slow the wire feed speed down compared to the .030 flux cored wire.

“Which one do you think then?” Said Joe.

I’d say on the spec for this wire you’d be better off with the .030. It’s suited to the welding Amp – output power of your welder and gives you the most flexibility.

Your little welding machine is going to have to work hard to even start to melt the .035 flux core wire. And strike an arc.

A little advice.

Even though flux core wire is more forgiving. Clean off your steel. Get as much rust off your work as you can. Get your weld edges as smooth as possible. That way your little welder won’t have as much work to do.

If you can find some .030 that also supports multiple passes. Then you can play with welding quarter inch or 3/16ths with the right prep.

Let’s talk To Andy next And Hear His Story

Andy has bought himself a Lincoln Electric 140

140 because he wants to try MIG welding with solid wire and gas. But to start he wants to weld with flux core wire.

Which does he use in his MIG welder? .030 vs .035 flux core wire?

Let’s help him make his choice;

Nice welder Andy? What is its Amp output?

“30 to 140 Amp, with a duty cycle of 90 Amp for two minutes.” Said Andy.

What size wires does the LE 140 take?

“Both .030 or .035.”

What will you be welding?

Andy said. “I want to play with the full range from 22 gauge up to 5/16ths. The Lincoln should up to that. I’m thinking of getting some of Lincoln Electric’s own brand wire. The Innershield NR-211-MP.”

​Ok, let’s look at the spec sheet for that wire.

A quick search of the Lincoln Electric site and we have the specifications.

LE rate the NR-211-MP for welding in all positions. The Lincoln .030 and the .035 flux core wires come in 1lb. or 10lb. spools.

Andy can your welder take the larger 10lb. spools?

“Yep” He said.

Great, the larger spools are usually economical to buy. Let’s take a look at ​Lincoln’s flux cored wire welding parameters chart. Great! It covers the .030 and the .035.

​LE Innershield NR-211-MP	.030	​.035
Welding Range (Amp)	30 – 140	30, 60, 115, 130, 155
Voltage Range (Volts)	14 – 19	​14 – 21
Wire Feed Range (Inches Per Minute)	50 – 300	50 – 275

Now that’s interesting. Your Lincoln 140 can go from 30 Amp to 140 Amp and the Lincoln .030 flux core wire is exactly the same. LE says the .030 Innershield can weld up to half inch mild steel.

How are you going to power your Lincoln Andy?

​”I’ve got it set up at home on its own 30 Amp circuit.” Andy smiled. “I checked the manual and that’s what it said to get the best out of it.”

Great, you can see that a 30 Amp circuit is plenty. Just by looking at the voltage range for both the .030 and the Lincoln .035 flux cored wire.

What’s the wire feed speed on the Lincoln 140?

Andy reached around and picked something up.

“I have the manual here, let me check it.” He said.

After a short pause and many ruffled pages.

“It’s 50 to 500 inches per minute.”

Perfect, the Lincoln .030 flux core wire is well suited to your welder. And I guess that makes sense as it’s Lincoln Electric wire

Now if you want to weld 5/16ths you’d need to bevel and do multiple passes with the .030 wire. And that’s fine cause the Innershield MP is capable of multiple passes.

Now let’s look at the Lincoln .035 flux core wire. The welding Amp range starts at 30 Amp and tops out at 155 Amp. You’ve your welder on a 30 Amp dedicated circuit and that’s fine to weld to the max with the .035 wire.

To be honest. It looks like Lincoln aims the .035 size of flux core wire at bigger welding machines. You can see that from its welding Amp range. Though you could certainly use it in your welder.

I think the Lincoln .030 flux core welding wire is better for you and your Lincoln 140.  You’ll get the most flexibility out of that wire.

The message for you here Andy is about what you’re going to spend most of your time welding.

Mostly welding thin plate then load up the Lincoln with .030.

You can get a small spool of .035 for quarter inch mild steel and above. You’ll be running your Lincoln 140 on the higher settings with the .035, which is fine for short bursts.

Also remember to switch polarity when you’re welding with flux core. Be sure you’ve the welding torch connected to the negative terminal. Or welding with your flux core wire won’t work.

Let’s Listen To Brad’s Story Next

Hi Brad, what are you up to.

“I’ve done a bit of welding before, I’ve some projects in mind that’s going to need some 3/16ths steel tubing.” Brad said. “The welds don’t need to be pretty. I need them good and strong. So flux core is fine. I’ve got myself a Hobart 190. It runs on 230 volts.”

That’s some machine, it should lay some nice beads for you.

​Brad said. “What do you think I should run in it, I’m looking at the Fabshield 21B, .030 versus .035 flux core wire?

We’ll look at the wire specs, but tell me about the 190. What’s its welding Amp range, voltage range and wire feed speed.

“K.”

Brad scratched at the bald patch on his head.

“It’s 25 to 190 Amp, up to 31 volts.” Said Brad.

Brad picked up his phone. A few taps on the phone later he said.

“Wire feed speed 40 – 700 inches per minute.”

We searched on the web for the wire specifications.

The Fabshield 21B is good for all welding positions, single or multipass. I said.

Fabshield 21B	.030	​.035
Welding Range (Amp)	25 – 125	55, 80, 120
Voltage Range (Volts)	14 – 16	17 – 20
Wire Feed Range (Inches Per Minute)	55 – 225	75 – 160

Looking at this Brad. Both wires are well within the capability of your Hobart 190. You could choose to load with either and depending on what you mostly weld.

Use the .035 for your thick mild steel and .030 for your thin metal. 

The only thing you’ve to watch out for is that you don’t blow through the wire. The wires top out at 120 and 125 Amp and your welder is capable of higher than that.

​”Not sure what that means.” Said Brad.

Ok, When the current becomes too much for the wire the arc starts to destabilize. Because it takes a certain amount of Amps to melt the electrode wire.

For example. Setting your welder more than 120 Amp would be too hot for the .035. And if it’s thin mild steel you’re welding, probably too hot for the base mild steel too. So keep that in mind when using .035.

It isn’t going to work for all you’re welding. Watch your Amp setting and wire feed speeds.

Choosing What Flux Core Wire To Use – 15 Points To Bear In Mind

Now you’ve heard the stories of Joe, Andy and Brad. You’ve a feel for deciding what flux cored wire to use, What might be best for your situation. And how to go about picking .030 vs .035 flux core wire.

1. Your Welder And What Its Can Do?

How many Amps are available?

​If your welder has to be set to the max to use .035 flux core wire. Then your welds will be tricky and take more time. You’ll be welding in short bursts. Because your welder is under powered for the job you’re doing.

2. What Size Of Spools Will Your Welder Take?

The smaller, cheaper, portable flux core welders typically take 1 or 2lb. spools of flux core wire. Look for the size of wire in the size of spool your welder will take.

3. How Thick Is The Metal You’re Welding?

For welding thin mild steel choose .030 flux core wire. For thicker steel metals (around quarter inch and a bit above) choose .035 flux core wire.

4. Are The Joints Straight And Clean Or Are They Wide And Variable

Wide and variable could mean you need more filler metal so .035 could be for you if your welder can melt it.

5. ​Flux Core Generally Produces More Spatter

So look for flux cored wires rated for low splatter to save yourself a lot of clean up. Or use Anti spatter spray on the surrounding area, (not on your weld joint). To protect your work piece.

6. Sometimes One Size Just Works Better With Your Welder!

Particularly if your welder can take both 030 and 035 flux cored wire. Experiment. Similarly one brand of flux core wire may work better regardless of the spec.

7. There’s A General Rule Of Thumb

Use .030 flux core wire for 190 Amp and under welders. And .035 for welders over that and .045 for 300 Amp welders.

That said. It’s also about matching the wire to the gauge of metal you’re welding.

8. Flux Core Wire For Single Pass Or Multiple Passes

Check if the flux core wire you’re choosing is made for single pass or multiple passes. 

Using single pass wire for multiple passes. Will cause your weld to be susceptible to cracking and failing. And none of us want that. Seek out the manufacturers spec for each wire.

9. Generally The Larger The Diameter (And The Larger The Spool Size) The Cheaper The Cost

So if both are within the welding range of your MIG. And cost to you is important. Then go for the bigger wire.

10. If Your MIG Runs Solid Wire With Shielding Gas And Flux Core Wire

You need to check the polarity is correct when you’re running flux cored wire.

Can’t strike an arc? – Check the polarity.

And while you’re at it. Check your grounding clamp has good clean contact with your piece. And a good ground connection.

11. Make Sure You’re Feeding Your Flux Core Wire Right

Pick the right sized groove on your MIG’s drive roll.  Use the right sized contact tip for the size of your flux cored wire. 

12. Flux Core Wire is Prone To Crushing

Because of its softer flux core center. Watch your wire tension and don’t crush your welding wire.

13. Watch Out When You Put Your Flux Core Wire Into Your Welder

That the wire doesn’t jump off the spool causing a bird’s nest so you get poor wire feeding.

14. Keep Your Welding Cord As Straight As You Can

Up to the torch head to get the best wire feed. And not kink your flux core wire.

15. ​Particularly With The Under 190 Amp Welders

Using .035 flux core wire you need to keep the wire feed speed down. And go slow to give your welder the best chance of working with the wire.

A Few Basics Of Flux Cored Wire

What Is Flux Core Welding Wire?

Flux core wire is one form of welding wire you can use in your MIG welder.

Popular because you can weld without the need for a separate tank of shielding gas. The flux in the center of flux core wire melts. And when it melts the flux gives you your shielding gas.

You’ll find metal around the flux core that gives you filler metal for your weld.

And that filler metal often mild steel, but it could be Stainless Steel.

Want to know more?

Click this link to see an article on the site all about it.

When Is Flux Core Wire Used?

You’ll find lots of situations where flux cored wire welding gives you an advantage.

Like outdoor welding. Because the weather can cause problems for your MIG welding.

Say it’s difficult for you to get to your welding location. And you want less to carry with you.

Or where you’re going means using a tank of shielding gas is tricky.

Then flux core wire welding is your buddy.

You can take a look at this article here to find out the why’s.

Benefits Of Welding With Flux Core Wire?

Flux core is more tolerant of rust and other contaminants.

Although clean steel is always recommended.

Solid wire in contrast demands clean steel.

Flux core is also more tolerant of the skill (or rather lack) of the user.

What To Do Next

​It’s best to choose the size of flux core wire based on your particular welder and what you’re welding.

Check the wire specifications and you shouldn’t go far wrong.

In the debate between .030 vs .035 flux cored wire, your own situation and what welder you have will drive the choice.

Check out these related articles.

Related Articles

Best Flux Cored Wire for Mild Steel And Banish Your Welding Frustrations

Flux Core Aluminum Welding Wire, Want It Now