Learning to weld aluminum

Look for a local tech school with evening adult-ed course offerings. If you can find such a place the welding class will typically be taught by a very experienced and now retired and bored weldor and are a great place to learn. For machines, look for a used Syncrowave 250, they can be found cheap at times and are a wonderful machine. Some of the newer units have more bells and whistles, but are more difficult to find cheap used.

I have thought of that, we have a local tech school and a couple shipyards, so welders are trained on a regular schedule.

For machines, look for a used Syncrowave 250, they can

That's much more than I was thinking about spending. But I'll keep my eye out, I could get the bug. Mikek

For the machine, you might be able to find a used "high frequency box" that allows you to use an AC tombstone or your Bobcat. They have some drawbacks, like no remote current control, but they can be used. The local used tool place here has a couple of these boxes that may be as old as I am (PDO). Those boxes were more common years ago.

You can get an estimate on the welding thickness your machine can handle from Ernie's rule of thumb of 1.5Amps / thousandth of thickness for aluminum. 1/4" ~ 250Amps.

On your pontoon boat, I would recommend getting some practice before attempting that one. Thin aluminum without a current control is going to be a very challenging project.

The advice about a vocational school is good. Another advantage is that you might be able to use the school's machine for the welding you want to do after you get into the classes.

Good Luck, BobH

Over 20 years ago I decided I wanted to learn how to arc weld. I already knew gas welding. So I took night classes and got pretty good at the various types of arc welding. For me, learning how to arc weld was a GREAT decision. When it comes to the type of welder for aluminum I would opt for a TIG machine. For several reasons. The first is capacity. I have a little 120 volt MIG welder. It is a great machine. It will make good welds on steel up to 1/4 inch thick with no trouble at all. If I pre-heat the steel then 3/8 is easy to get good welds on. By good welds I mean welds that would pass inspection by a weld inspector. The same mig machine will just barely weld .050 thick aluminum. And you need different liners for the aluminum MIG welding wire to run in than you do when running steel. So if welding aluminum with a MIG machine you really need a 220 volt machine and a liner for aluminum wire. And you will need one kind of gas for aluminum and another type for steel. I am assuming that any welder you get for aluminum welding will also be used for steel welding too. On the other hand, a 220 volt TIG machine will weld thicker aluminum than a comparable MIG machine because of the way the TIG process works. When buying MIG wire you have to buy spools of wire because that's the way it comes and the way the machines work. So you end up buying at least

2 lbs of welding wire for each alloy of wire. With TIG if you need to do a special job you can just buy a few 3 foot lengths of the wire you need. There many commonly available TIG wire alloys in several different diameters that most weld suppliers keep in stock. I once had to weld up a hole in an old aluminum motorcycle fender. This hole was bigger than a quarter but smaller than a half dollar. The most important thing was for the weld repair to match the color of the existing fender. So I bought several different alloys of aluminum wire to try to get the best color match. But I only had to buy a few pieces of each alloy instead of several 2 lb. spools because I was going to TIG weld the fender. And I did find a good color match. When the fender repair was finished it was invisible. Anyway, TIG welding is slower than MIG welding but is much more versatile. And you can generally get by with just one type of gas for TIG welding. I use argon for TIG welding but for MIG welding I use argon, CO2, and C25, which is 75% argon and 25% CO2. One really nice feature of TIG welding is the ability to weld metals of wildly different thicknesses together. So you can, for example, weld a heavy walled pipe to your thin walled pontoon. I have both a TIG and a MIG welder and use them both but if I could only have one it would be the TIG machine. I hope my long winded reply helped and didn't bore you too much. Eric

You can stick weld aluminum. I think that your Bobcat is an AC/DC machine so you can use it as Aluminum is best welded with DC rather than AC.

See

My experience was that it took a little getting used to use as the deposit rate is very high and you need to feed the rod a lot faster then welding steel, but it really isn't difficult to do.

Now, having said that I'll also comment that, although you mention

1/4" which shouldn't give you any problems at all, it is, like stick welding in general, not the best system for welding thin stuff although if you have some experience in burning holes and frantically filling them up you'll have better luck :-)

Check out the Everlast products . I bought the DX250 TIG/stick/spot machine and I'm happy . Total invested including argon tank under $2k .

I don't think I'd want to try AL without "live" amperage control, either foot or fingertip.

Good Syncrowave 250 complete setups have been known to go for

Whew, smells like a brain fart in here... Ernie says that 1.5Amps / thousandth is a good starting point, which is true. You can also weld

1/4" aluminum with around 200 amps depending on the joint configuration and preheat, not the 375 predicted by 1.5A/thousandth.

Once again, demonstrating the hazards of posting while pre-occupied.

BobH

Thanks, your input was very welcomed. Mikek

Actually my welding amperage rule is 1 amp per 0.001" of thickness, for aluminum and steel, in a flat, butt-weld position. Full penetration, single pass, with no bevel.

Add 1/3 more for an inside fillet weld. Subtract 1/3 for an outside fillet weld

If you bevel your edges you reduce the amperage needed to melt it.