This Doesn't Have to Be So Hard: TIG Welding Aluminum Fillets

Added: 2026-05-11

[00:00:00]Aluminum fillet welds can be a real challenge. The puddle won't move. It's hard to control. It's difficult to see what you're doing. The filler metal melts off when you don't want it to. A lot can go wrong. But there are just a few tips that can help this go a lot better. So, before attempting this type of joint, make sure you can reliably run some beads on plate. You know, adding filler where it needs to be, controlling your amperage and travel speed, those types of things. Now, we're going to dive into uh some T joints here, and I'll show you a few things that keep a lot of people stuck when they start off with this joint. Here's how it goes for most people who I've helped. They've watched enough YouTube to know how to prep their tungsten, and they might even round a ball on it, which uh I don't typically do, but we'll do it here in this case. They go with a standard electrode extension, and they're going to set their machine based on the old rule of thumb, 1 amp per thousandth of an inch. So, for 1/8 inch material, that's 125 amps. Now, let's see how that goes. When I start here on my material, um, I know that I'm going to pause there at the beginning and let things warm up a little bit. And as I do that, I'll start to establish a little bit of a weld puddle before I ever add any filler metal. So, here's what that looks like.

[00:01:20]If you start there on the end, you're going to start to get a little bit of a puddle, but you're going to have that itch to add some filler to it, and it's going to take a little bit of time. Now, it's going to be a long time when you're starting to move forward, and that puddle just isn't pushing down into the root of the joint. There's more of a hole there. And look how that filler metal just dropped right off ahead of time, bringing a bunch of contamination into the weld puddle. This isn't going well and it can be really frustrating to experience this after you've run some really nice beads on plate and you wonder what on earth is going on. Well, the reality is there are two simple fixes that can make this go a whole lot better. And I'm going to show you how to fix them really quickly. Now, in the end, the weld isn't terrible, but it certainly isn't what I was hoping for, and I didn't get down into that joint.

[00:02:11]The first reason is the electrode was not extended far enough to really tighten my arc length up because the cup will hit the sides before I get in tight enough. So often you need a little more electrode extension when you're welding an inside corner uh like this compared with an outside corner or butt joint.

[00:02:28]Now the other thing is there are three different legs carrying heat away. And so I'm going to need more amperage to overcome that. So I'm going to turn it up. 150 would probably be enough, but I typically like to run at 170 amps or so on 1/8 inch thick material since I have a foot pedal to control it. I'm running this HTP Independence 210. This has been an outstanding machine over the last 6 months or so that I've had it. I mean, it's portable, well-built, durable. The starts and arc are as good as any machine that I've run at all. So, I'll link that in the description. I still need to camp out for a little bit to get things established and start my weld puddle. But look, now it's flowing down forward into the root of the joint. And I can just add that filler metal right up to the front leading edge. And I'm still using basically full pedal here on this thing. And that allows me to travel faster. But again, 150 amps would be sufficient. I'd just be traveling a little bit more slowly. There's a balance between travel speed and amperage. Um, but you do have a little bit of leeway uh as you go. Now, here towards the end, the heat is building in the material, and I need to back that off. So, you can see I'm backing off rapidly. In fact, in this case, it wasn't quite rapidly enough, but still not too bad. And then at the end of my weld, um, as I come up here, uh, on the runway, and I'm backing off my amperage, I'm going to get ready to add just an additional extra bit of filler there to fill in my crater. And you can see how compared to that first section, it's a lot more smooth, and I'm a lot happier with how that turned out. So, those two improvements make a huge difference, and that's where a lot of people get stuck.

[00:04:02]I'm just running my standard aluminum settings. Typically, I run 75% uh balance. That might be 25% on your machine. And I run an asymmetric uh amplitude if you have that. I'm at 90% on electrode positive. And then I'd run at 90 hertz, which is good middle of the road for this thickness. Now, I don't typically ball my electrodes like I did in that example. Um I typically leave a point there. Not that it's better, but I just don't think it's enough better with a ball to be worth the effort. Now, something that's pretty useful to know how to do is to be able to tack without filler on aluminum. And this can be a challenge because often the material will just ball up and separate. But having that higher amperage setting allows me to do this. Let me explain how I do it. So, I'm going to line up right there on the joint and I rest my cup on the material whenever I can. And then I start with a lower amperage and get a puddle established and then floor it.

[00:04:56]So, watch right here. Lower amperage then floor it. I'll slow that down a little bit so you can see as I start up with that lower amperage, I get everything positioned to center and then I floor it right here. Increasing the amperage that brings the material together and gives me a nice little tack. Let's look at it one more time.

[00:05:17]So, right here, taking it pretty easy on the amperage. A puddle's starting to form. It's even on both sides. I floor it and it fuses together. But this is in real time now what uh you're looking at. So that's a pretty useful skill. It's definitely not as strong as attack that has filler metal, but it certainly is really handy when you need to assemble things to be able to just stick them together like that. So that's another tip for you. Let me show you something else. Now positioning is a pretty big deal right here. So I like to whenever I can position myself such that I'm welding somewhat towards myself and that helps with that torch angle. And then I hold my filler metal in such a way that I can feed it. Now, feeding the filler metal isn't as big of a deal as a lot of people make it out to be. If you can't do that, you just do a little at a time.

[00:06:05]And that shorter arc length from the electrode extension as well as the increased amperage just makes everything flow smoothly. Not that this is the internet's weld of the week, but uh it certainly does run much nicer. Now, if you aren't proficient at running a weld beat on plate, you know, they these are really what we focus on a lot in my online courses because this is where you learn to control your travel speed, your amperage, your angles, um all of those sorts of things, where to add filler metal, and then those skills directly translate, but you do have a few uh nuances like we talked about in this video with that particular joint. If you enjoyed this or learned something, let me know by leaving me a comment or hitting that thumbs up button below. And if you want me to walk you through the whole journey learning how to weld step by step in a way that isn't intimidating and I keep it affordable, I have some online courses linked down in the description below. So, be sure to check those out. Thanks again for tuning in.

[00:07:00]We'll see you next time.