Why Does My Filler Rod Melt Back?

Avoid the most common beginner mistakes and get the TIG welding basics right. Here I lay out arc length, torch angle, and show why the filler rod sometimes melts back. At the end is a video using these fundamentals to show how to dab and weave.

Stainless filler rods balled up on end from too long arc length.

What is Arc Length?

The distance from the tip of your tungsten to your work piece (whatever you are welding on) is your arc length. Almost all problems faced by new TIG welders are either from arc-length, or some form of contamination.

As you can see above, technically, the arc cone branches off the tungsten a little higher than the tip (in the taper), but when you are practicing and learning, thinking about it emerging from the tip of your tungsten in a triangle shape that spreads out as is travels is a good idea. 

Arc Length Training

You want to hold an arc length around 1/16 of an inch above your puddle. The problem is you DON'T want to be looking or checking your arc length while welding. If you do, your eyes will cross the bright arc and you'll have difficulty seeing your puddle and surrounds.  As you get more experienced, you'll be able to tell from how your puddle behaves, with a little guidance from your peripheral vision, if your arc length is correct.  But how do you first learn arc length control when you're new and learning? 


Dry runs. Hold a 1/16" filler rod flat on your table or a plate.  With your welding machine off, hold your torch to the side of the rod and try to match the 1/16" gap with how far your tungsten is off the table (your "arc length"). Pull the torch forward and try to maintain the same arc length as you go.  This will help train your hand and muscle memory how to hold a steady arc length while moving forward. 

Torch Angle 

Torch angle and arc length are connected, but we'll get into that in the next section.  It's a good starting point to hold your torch at around a 15-20 degree forward angle.

There's nothing wrong with holding it vertical, but it becomes harder to see what you're welding because you have to get a lower line of sight.  A forward angle also helps preheat in front of where you want to go, and the puddle follows heat. Don't worry about getting an exact torch angle. There's a ton of leeway here and arc length is more important to get right. A slight forward angle just helps set you up for success while learning. 

Why Filler Rod Melts Back 

This is one of the most frustrating and common things that happens when you're learning how to TIG weld. But the cause is simple. It's arc length.  When your arc length lifts up too high, the arc extends outside the edge of your puddle.  The higher you go, the farther it spreads out from your tungsten, like an inverted V, hitting your filler rod and melting it back (balling it up) before you have a chance to consume it with your weld puddle. 

 Below is an image of an actual TIG arc melting back a filler rod.  You can see on the left the arc is tight and small (the filler rod is off to the right side).  As the torch lifts and the arc length increases, it spreads to the side and melts the rod back.

You might be thinking, but couldn't torch angle be the reason?  Yes and no. As you can see below, even with an extreme forward angle, as long as the arc is tight it doesn't melt back the rod.  But as I lift the the tig torch and increase my arc length, it spreads out and shoots forward, melting and balling up the filler rod.  The difference is that the more forward the arc length, the TIGHTER you have to keep your arc length.  You can see I don't have to lift the torch as high with the forward angle as when it's vertical.  

The video below reviews these basics, as well as some other tips, and shows how to dab and weave. Check it out! 


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