How to Prevent Undercut Welding?

Being an expert at something doesn’t mean you’re expected to be perfect at everything.

It’s human nature to make mistakes, especially if you’re only starting.

That stage at the beginning is usually where mistakes are all clumped together, leaving you vulnerable to making even more mistakes in a messy chain reaction.

Both beginners and experienced welders are bound to make these errors that affect the quality of their craft.

And one common mistake any welder tends to do is undercutting the metal!

What is an Undercut?

As mentioned earlier, undercutting is a pretty usual mistake welders would make, but it’s also one of the worst ones.

Undercutting is a primary cause of the welded metal reduction, so you can tell how exactly it became “one of the worst”.

Because it lessens welded metal, it weakens the weld that’s supposed to bind two pieces of metal together.

In that case, you welding it is counterproductive, don’t you think so?

And not only that, but undercutting leaves your slab of metals looking like a big, old mess because there are bits of metal spattered everywhere that only make your craft appear nastier than before you touched it with your inert metal gas (MIG)!

Causes of Undercut: Know The Basic Traits

Not Fast Enough, Not Slow Enough

Rushing anything rarely ever brought back good results, but slow down too much and you won’t get anywhere at that rate!

That’s why travel speed plays a significant role in undercutting.

Too fast, and your base material won’t have a lot of time to take to be welded properly, which causes the material to spatter and crack.

Too slow, and your weld will penetrate too deeply and eat into the base material.

Your Worst Angle

The common theme for these causes seems to stem from “too much” or “too little” of anything.

In this case, having your rod pointed upright to where you’re going to weld is not as effective as you’ve imagined it to be.

An upright rod (or electrode) will damage your base more instead of welding the two metals together.

The same goes with angling your electrode near-horizontal against your base material, but a low-angled rod will aim more at the upper material than an upright rod that damages the lower material.

Either way, this goes to show how working while doing something as simple as using the improper work angle can spell disaster for your weld.

How can undercutting be avoided

Too Far!

This next cause is somehow connected to the last one. Or it’s a bad habit that newbies would do while they use a poor work angle.

And that is neglecting the arc length. Understanding the blueprints for welding can solve the issue sometimes.

Now, the arc length pertains to the distance between the tip of your electrode has to the area you’re welding. Pretty simple stuff, right?

Well, you probably don’t know yet, but this can spice things up EXTREMELY badly when not paid attention!

Because the arc length is closely intertwined with your voltage, you can already imagine how that affects your base material.

Having your rod a good distance away from the metal means there’s a wider arc length, and the farther it is, the more the voltage will have to kick it up a notch to heat the metal. 

“Does that mean having the electrode sit close to the metal is a good thing?”

Nope, that’s no good, too!

With how excessively near the tip of the electrode is, its voltage will be too low, as well. And you can’t exactly do much with that low of an amp!

Steps to Prevent Undercut Welding

Keep a Close Eye

Multitasking is one of a welder’s best assets yet!

Arc lengths, currents, angles—all of these you’ll need to pay close attention to if you want to weld something without undercutting its material.

So, all you need to do is list down everything you need to keep track of and remember them.

First, the working angle.

You wouldn’t want it to lean too far back that the electrode’s almost horizontal against the base. And you don’t want it leaning in too much that it’s vertical to what you’re welding on.

Both of these scenarios will result in undercutting, so what can you do?

Meet at a solid middle ground!

Go with a 45-degree angle. This way, you can see how you’re welding is going AND know where exactly you need to go.

The same applies to your speed. You’re no rabbit beating the tortoise in a race because, well, welding’s not a race!

Per minute, you should be able to weld up to 3 to 6 inches; nothing more, nothing less.

Your arc length plays a huge role in all of this.

If you want to maintain that estimate of 3 to 6 inches per minute, then you better have your electrode no more than a diameter from the base material!

Know Your Electrode

Since we’re talking about electrodes, you should know that there’s not only one welding rod available for welders everywhere!

But be sure to check on how thick the metal you’ll be welding, is first!

Once you know that, you can now pick which electrode you want to use.

For a bigger welding area, you’ll need a 1/16-inch electrode, so your arc length should be 1/16 inches, too.

For smaller areas, a 1/8-inch electrode can do the trick, and the same goes for its 1/8-inch arc length.

To repeat what’s mentioned earlier, you’d want your electrode no more than a DIAMETER from the base material, you hear?

steps to Prevent Undercut Welding

Keep Hands Steady 

All of those angles and control will require a steady pair of hands for a hands-on job like welding!

Because steady hands mean better chances at a clean weld, and a clean weld means there’s little to no undercutting that occurred.

I bet the longer you practice a ton of trial runs, the better your hands will be trained to stay still.

Final Words

Mistakes tend to happen in any area of expertise, and it’s all up to you to grow out of it.

By identifying how one of the welding’s most common issues happens, you’ll be able to learn to go past that!

Sure, you can’t fix what’s done, but you CAN keep it from happening beforehand!

So knowing how to prevent undercutting in welding, that’s one less problem for you to face as a welder!

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