Arc Welding 101: Wire-feed welding, stick welding with the same machine

Q: I would like to know if a wire-feed welding machine can double as a modest-amperage DC shielded metal arc welding (SMAW) machine if I attach an electrode holder to the output.

A: Power sources are designed to provide constant current or constant voltage.

Gas metal arc welding (GMAW) is constant voltage, while SMAW is constant current. All the different amp and voltage curves and droops can get long and complicated to understand and are a bit too technical to go into here.

Here’s how a fellow once explained it to me: The two power sources are like comparing apples to oranges, and when you try to work one off of the other, “it just don’t work.” (That’s a direct quote from a guy I used to work with in the field. He used that reply quite often, on a variety of topics!)

Most of the welding manuals out there explain power sources if you want to look into the technical explanation.

As for aluminum SMAW, I have used it to some extent and can tell you it’s good only for thick aluminum. Aluminum has twice the expansion of mild steel and is a much better conductor of heat. This can cause distortion, and it’s easy to blow a hole in the metal before you realize it’s happening.

Thick aluminum should be preheated to somewhere between 300 and 400 degrees F before you weld it. When I say thick, I mean anywhere from a half inch and up. That’s on my scale of thickness, though, so you should research the actual measurement.

You need to use the direct current electrode positive (DCEP) and keep a really short arc as you drag the electrode without oscillating (weaving). Most specifications on critical joints won’t allow aluminum to be stick-welded.

Be sure to keep the electrodes dry, because moisture in the flux will cause it to dissipate and flake off. Also, it’s important to remove the oxides before welding and postclean the weld because the leftover residue is corrosive.

I know it’s a pain to convert your machine, but that’s probably your best bet unless you want to buy an AC/DC SMAW machine. Then you could always go with an inverter—but that’s a whole other story.