How thick of material can you weld at 100-120 amps?
I think you are right about getting a unit with AC. Better to have it and not need it, than need it and not have it.
dunno at 100, like i said mine is a 200 and I welded 1/2'' material no problem (with enough chamfer of course), you could weld thicker but it's all based on how quick and what's the acceptable warping if you heat up the pieces too much. the other thing that i noticed when you weld thick pieces is the torch gets really hot, so if you do that on a constant basis you should look at a watercooled torch but i don't think that's something you need unless you plan to do it a lot (not worth the expense otherwise, just have to take a break and let it cool). one thing i noticed when they list the material thickness to me it looks like it's based on enough penetration on 1 pass to create a weld strong enough to compare with the strength of the material you are welding (like for example they say 1/4'' thick for 200Amp tig welder but that's really a walk in the park for the one i have, so that's where i got it from). Aluminum thickness rating is also lower than the steel (or requires more amps).
100 amp is probably good for 1/8'' or maybe 1/4'' with multiple passes, it's really how much penetration you get, you can still surface weld any thickness but the question is if it will be as strong as the the pieces you weld. if strength is not a concern you can weld them together but at a certain thickness you will also develop cracks in the weld if there's not enough penetration from what i could figure out with my own experiments, but since i am far from being an expert and just a backyard/home garage junkie i could be wrong on any of the statements above so anyone who's a welder by profession or more experience and knowledge please feel free to correct any mess in my post.
