Tig welding without filler

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All,I am new to tig welding and have learned much from the posts on this forum.I have mig and stick welding experience from a junior college class I took 10 years ago.  I have been wanting to learn to weld aluminum.  I recently purchased a Lincoln Precision tig 225.  I have dozens of sheets where I've practiced my lines on aluminum plates.  I decided to try one of the projects I have lined up.  The first is a custom mail box that replaces a rusted out one build into the wall next to my front door.  I first tried to do this with thin stainless.  The sheet metal was just too thin for my inexperienced hand. What size of stainless is practical for such a project?   I ended up finding some .090" aluminum and made the box with that.What I found was that I was mostly just melting the edges together by using the tig welder as a torch.  This made a box that looks pretty decent.  Since the metal is thin, using filler just slowed down the movement and caused me to make holes.  How structurally sound can a weld be without adding filler.  I have several other projects that will hold weight.  I'd like these ones to be stronger.For reference, I welded with about 115 amps using a 3/32 ceriated tungsten.  I didn't use the pulser, I haven' seen much benefit.  The AC balance is on auto, I'm not sure how to best adjust this either.  I don't use much post flow as it doesn't seem to make much difference.Sorry for the narrative, my questions are:1. What is the thinnest metail (aluminum, stainless, etc) that is practical to tig weld?2. How strong is a quick weld along an aluminum corner weld?3. Any advice on settings would be much appreciated.ThanksChris Attached ImagesLast edited by heychris; 12-05-2010 at 08:38 PM.
Reply:See below pic--red llnes outline hot crack.If you're no filler welding 6000 series aluminum--that's invitation to hot cracking.1. What is the thinnest metail (aluminum, stainless, etc) that is practical to tig weld?--depends on your definition of practical, depends on the lowest machine setting,size of electrode---and although this shouldn't count--operator skill.--depends on the joint, the end result desired, etc. 2. How strong is a quick weld along an aluminum corner weld?....well...your quick weld cracked as it was being welded---if you bothered to notice.On the other hand, no filler welding is a great way to save money, time and hassle.A corner weld with filler, prep--all those nonsense items--is extremely strong3. Any advice on settings would be much appreciated.http://weldingweb.com/attachment.php...1&d=1291600315 Attached ImagesBlackbird
Reply:*On my Sync 250.1-Most people can comfortably weld .025"material, with a little practice.  With experience, materials as thin as .005" are TIG'able.  (practice on soda cans)2- With a little practice you'll be able to weld full speed while using rod, just keep at it.  Make sure the aluminum is pretty clean, it'll go much better for ya.  Alum doesn't like fusing much, it tends to crack a lot.  I always add rod to Alum.  Steel & stainless do ok with it though.3-for .090" 5051 sheet: Clean the alum first.   I'll usually go with 15-20 psi argon, @ 150amps.  Ac balance cranked all the way up to 10.  (for really thin, or cast my balance is around 6-8).  post flow around 10sec.  3/32 zirtung usually.I don't bother with the pulser personally.  Learn to feed the rod correctly & you'll never want to eitherYour mailbox should hold up fineBuy American, or don't whine when you end up on the bread line.
Reply:2. How strong is a quick weld along an aluminum corner weld?....well...your quick weld cracked as it was being welded---if you bothered to notice.
Reply:Rather than retype a bunch of info, read thru this thread.http://weldingweb.com/vbb/showthread.php?t=46304Tig alum is a tough way to jump in and try to learn tig..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:Thanks for the quick and helpful replies.  I've spent hours reading posts and learning quite a bit.I apologize for the picture confusion.  Those aren't cracks.  I sanded the faces of the aluminum after finishing.  Those are just marks left by the sander.My aluminum is 5052.  Is there a difference in welding strength between 5000 series and 6000 series? Obviously the 6000 series material is going to be stronger.I agree, it'd be easier to start with steel.  I've done hundreds of lines on steel as well as aluminum.  I'm having a hard time making the jump from lines on plates to corner, fillet and butt welds.  Out of curiosity, does anyone have a suggestion for corner welds on thin metal?  How do you keep the the two pieces of metal from melting away from each other?Thanks.Chris
Reply:One more question.  Are there guidelines relating thickness of metal to diameter of the tungsten?
Reply:Regarding guide lines for material thickness to tungsten thickness, google "miller weld calculators".  They've got them for stick, mig, & tig.  They give the tungsten size to material thickness w/ suggested amps for different type of welds (butt, fillet, lap,etc). Good luckMy toys:Mobile Set Up    Miller Bobcat 225NT    Oxy Acetylene cutting set up    Red D Arc 12VS wire feeder    Spoolmate 3035 spoolgun     Scratch Start TIG DCMiller Elite auto hood
Reply:I use the miller tig calculator often. I am surprised I missed that. how much difference does going from 3/32 to 1/16 make?
Reply:Originally Posted by heychrisI agree, it'd be easier to start with steel.  I've done hundreds of lines on steel as well as aluminum.  I'm having a hard time making the jump from lines on plates to corner, fillet and butt welds.  Out of curiosity, does anyone have a suggestion for corner welds on thin metal?  How do you keep the the two pieces of metal from melting away from each other?
Reply:enough flat late. move to a lap joint. you'll learn to concentrate the heat on the plate and push the puddle to the edge of the upper plate. move to an inside corner..you'll need more stickout to keep a short enugh arc length,  and more heat..on an outside corner, you'll need good fitup to keep the edges together..and there is the cocnept of good enough for a government job.. your bead is good enough for a mailbox, but not a trailer..welcome..
Reply:This is all excellent help.  Thanks again.I'm big on cleaning before welding.  I use an angle grinder with wire brush (not sure it's stainless) followed by acetone.I should go back to some basic welds.  I think it's all good practice and I appreciate the opinions.I use a aircooled #17 torch.  I have both the medium gas lense  45V28 and the smaller collet body with gas ports  10N32.  When is it appropriate to use the smaller collet as opposed to just putting a smaller alumina cup on the medium gas lense?