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I want to do some aluminum welding, have never done it, but I have welded lots of steel and stainless with Tig , Mig and stick.. I have heard I should get a spool gun, will that work with either my tig or mig welder? Both are Lincoln machines, does the spool just hook up to either of these machines? Dave

If your TIG welder has an AC option then you’re all set to weld aluminum, nothing to buy but filler metal.
I weld a lot of aluminum wth the TIG, the puddle acts a little funny compared to steel but it welds easy enough.

A spool gun would allow aluminum welding with MIG, they can be expensive.
I’ve never tried one, hear it’s easy, point and shoot, but may be hard to get a consistently strong weld, takes fiddling with settings.

I've watched a youtube video where a guy shows how to weld aluminum with MIG using the standard gun, not a spool gun. IIRC he recommended a particular wire that was stiffer than the normal aluminum so it would push thru the tube and gun without buckling. Might be worth a try if you can't swing buying a spool gun.
Unfortunately don't recall the link to the video - Just ran across it in youtube browsing one day.

I've used a spool. It's better on 1/8" and up. It'll burn holes in the thinner stuff. Otherwise, if you clean the area you want to mate, it works pretty well. That means removing the oxidation. If you don't, welding will be a mess.

I had a Miller set up for welding aluminum only. But before I could play with it, it had to leave.

On my current Miller with the spool, it is already set up for that equipment. A place for the tank, connectors for the leads, etc. To adjust the settings for welding aluminum, you turn on your gas of choice and trigger the spool. The machine will read that you are in aluminum mode and will allow you to adjust at the spool gun itself. To go back to the MIG gun, trigger that one and it will switch back to the steel wire feed controls. This machine also comes with a bit of a cheat sheet. If you look at the upper part of the picture, you can see that they give you some basic settings for the particular type and thickness of metal that you are welding. Good starting points.

The alloy number is 5356- - - -it's stiffer than other MIG spool wire, and is less likely to "bird's nest" in the drive roller. Hre's a video with a few other handy tips, like using a slightly oversize contact tip. I'm going to get a spool of aluminum wire and try it!



Jerry

would have to be welding a bunch of the right kind of aluminum parts
to be worth the effort to use a spool gun.

biggest thing you need is enough power to get the puddle quickly.
things like using stainless steel backing also helps.
inverter machines weld a little different then transformer machines.
on thin stuff you can ofttimes do outside corned with out filler.
if you do AC pulse it can give a nice pattern

one thing is running AC is noisy compared to doing steel and other DC

I have a Miller Dynasty 350 with a water cooled torch which I seldom use. I have an old Miller 251 with a push pull setup that we use for most structural welding we have to do on our trailers. A couple of years ago I bought a Miller 212 with a spool gun dedicated to it. This is the welder I use for everything I do. I don't weld a whole lot at one time and I guess the spool gun would get heavy over an extended period. Occasionally I have to use the 251 tp get into a tight place. But the 212 is my favorite for welding aluminum. Of course you get used to the machine you use the most. One of the local welders here uses nothing but tig on aluminum and won't hear of wire. The factory that builds our aluminum trailers uses nothing but wire for new construction as well as repairs.

That's the one I saw. I may give it a try at some point as well. But my next project is welding some stainless seat brackets for my boat. I need to find a small bottle of tri-mix gas for that.

I don't bother with pre-mixed gases- - - -I have a bottle of CO2 and a bottle of Argon, T'd together upstream of the welder, and I adjust the regulator pressure to create my own mixes for mild steel and stainless. I haven't tried aluminum yet, but the tip about using stiffer wire sounds promising. My mix for stainless is about 90% Argon and 10% CO2. The weld is a little dark, but a quick buff with a stainless wire brush in a die grinder slicks it right up.
Jerry

I use argon in the TIG for all metals. Argon/CO2 mix for the MIG, steel only so far.

One project I'm considering is converting an aluminum oil pan for a 4.2 L Atlas engine to a rear sump configuration for use in a stovebolt with a straight front axle. That will involve more or less cutting the pan off a couple of inches below the engine block and fabricating a complete pan out of 12 gauge aluminum sheet metal. That should be an interesting project.
Jerry

If you make all the welds sharp, square corners, you won't even need much, if any filler rod. Its referred to as fusion welding. I use a continuous tight circular motion, pushing the puddle along the ridge. I am guessing that you already know that.

I've fusion-welded literally miles of stainless steel thinwall tubing in diameters from 2" to 6" while I was a welder/mechanic at Gallo Winery in Livingston California. During a modification of the plant piping before the harvest season began one year, we ran 8 miles of new 4" pipe. It was installed anywhere from 12 feet to 40 feet above ground level.

It's a little difficult to fusion weld with a MIG machine- - - - -my TIG isn't in working shape yet.
Jerry

A spool gun has to be run on a constant voltage machine, so a MIG machine.

I have a 15A spoolgun I used on a Millermatic 251. This set up is nice because you can adjust your inrush wirefeed speed. With a MIG welder, the power supply is designed to supply as much current as needed to maintain the voltage you have set. When starting the arc, the moment the wire touches the work, the current goes from zero to maximum deliverable by the power supply. The current on a MIG is NOT adjustable by itself, the wire feed speed actually helps determine the current a MIG supply will put out. With aluminum, particularly if your stickout distance from the tip is a little to long, the maximum current travels through the wire and 'vaporizes' it before it gets a chance to get an arc started on your work piece. This also burns the wire back into the tip, so you either replace the tip or get the aluminum dug out of it somehow. By adjusting the wire feed arc initiation speed, the wire is fed slower until the arc starts, and once the arc is going, the wire speed goes to the setting dialed in.

On my last job I had 18 4' x8' sheets of stainless to be welded in a box. Airtight seams. I wanted it TIGed but they convinced me to let them try a MIG on it. It came out very nice and way faster. I was pleasantly surprised.

I got some flux core stainless wire and reinforced some boat seat bases. It was my first attempt at welding stainless (I did make a couple of practice passes on scraps), but they came out nicely. Wasn't much different than welding mild steel.