Starting to research Tigging Aluminum

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Hi,I've posted in the Intro section as a new forum member. I went through all 330 of the project posts to get familiar with the forum and liked what I read. Decided to join I do some mig welding (hobbyist only) and have a desire to do some metal sculpting which will include metals other than steel. So learning to Tig seems a resonable goal.My first two questions are:1) can you Tig aluminum that is greater than the recommended maximum w/ multiple passes?that is, if I have a Tig that can weld a maximum of 1/4" in one pass can I tig 1/2" with multiple passes? (using the same welder)2) Using a standard mix of gasses (let's say 50/50 of argon/helium) will this be satisfactory for all types of Aluminum? I did notice that people will custom mix their own gas, but is it always argon/helium?thanksRobTA 185Lincoln 180cEconoPak 50 PlasmaSouthBend Heavy 10Clausing 8250 MillSouthBend Shaper 7Chevalier Surface GrinderPowermatic 15" vari speed Drill Press
Reply:For general alum tig, you need a machine with enough amps to do the material you are working with. You won't weld 1/4" alum with a small 165 amp AC tig. You would need about a 250 amp machine to do 1/4". Most tig is all done with 100% argon. You can use helium mixes to slightly extend the range on a machine, but not much. You might be able to do 1/4" with a helium mix and a 200 amp machine maxed out, but you'd really need to know what you are doing. It is possible to do thicker alum using DC tig and straight helium, but that's not something the average guy usually does, and when you see what  pure helium costs, you'll probably need to sit down.For most guys a 200 amp tig is enough to do 3/16" alum under most circumstances. Chances are you won't need to do thicker alum. If you do, there are better choices out there for that, like mig. Tig usually is a good choice with thinner materials not thicker material.Understand alum tig is not the easiest process to master. Expect to spend hours and hours learning basic heat control on steel 1st. Then maybe you'll be ready for alum. This isn't something you'll learn in a weekend or just farting around. You'll probably need a couple hundred hours of dedicated hood time to even begin to learn alum..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Biggest thing with aluminum is getting the material clean and not being afraid to add filler quickly once the puddle starts. There is a very fine line between a puddle and a hole and the only thing keeping it from dropping out is the ability to recognize this and control your heat.
Reply:I have no trouble tigging 1/4" on my HTP 201.  If you get into heavier stock, you will need to preheat it.  My prelim machine settings would be wide open amps, 75% and 140 Hz.  You need to watch duty cycle, however.  Actually, when the cable gets hot, I stop for a while or I'd burn up the torch.- "If ya can't be handsome, ya may as well be handy!"   HTP Invertig 201Lincoln Power Mig 255CLincoln SP125+Thermal Dynamics Cutmaster 38
Reply:It doesn't have so much to do with just the thickness. Its more about volume. I could weld 1/2"  thick material with 150 amps as long as it was a very small part. But as the volume increases you very quickly lose the ability to weld it. I think the thickness rating is based on big parts/sheets where your not able to get the whole part up to flesh searing temps.www.performancealuminumfabrication.com
Reply:DSWvery helpful info pertaining to 1/4" aluminum. I may be asking too much as a hobbyist to expect $1200 (used) welders to perform these tasks.IronmangqI'm real good at putting holes in stuff. Keeping things clean can be a challenge, but I can do it.Garauld and  travisc454  This puts things into perspective for me. I don't anticipate long runs on thick aluminum.Based on these responses I'll lower my expectations for the thickness of aluminum (because I can go to my mig for slightly larger sizes)I'll get a tank of Argon as well.I noticed I put this post in the wrong category. I'll walk over to the general area now.RobTA 185Lincoln 180cEconoPak 50 PlasmaSouthBend Heavy 10Clausing 8250 MillSouthBend Shaper 7Chevalier Surface GrinderPowermatic 15" vari speed Drill Press
Reply:You can certainly weld that thickness alum with a machine costing less than $1200. There are tons of older industrial quality AC/DC tigs out on the market right now. I frequently see machines like Zap's 330AB/P for $500-800. Plenty of amps to do 1/4". The down side is they are very large, very heavy, and want 125 amp plus service on 230v to run in at the upper end. You won't get that kind of output on a 60 amp breaker, but they will do say 1/8" on one. No bells and whistles, but plenty of power in a solid machine.$1200 would also get you a nice  Used Syncrowave 180 or Syncrowave 200. The 180 would get you 1/8" no problem, 3/16" if you push it and the 200 would get you solid 3/16". Several guys here have picked up very nice, almost new Syncrowaves from hobbyist's or small shops who simply can't justify the "toy" any more..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan