Thin Stainless -Tig the best option?Advice please

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I'm looking to fab some maple evaporator pans out of 20 or 22 ga stainless. I've had stick and mig machines already for a long time, my mig is the smaller hobart handler set up for .023 wire. Some of the guys at work are advocating a try with the mig, stainless wire, and a specialty gas mix.  The folks on MapleTrader pretty much say tig.  I looked at the little tig machines like the ThermalArc 95s, wondering if this would be a reasonable cost effective solution for me for this type of application?  Appreciate any input. I searched all the posts with maple in them and read about 1/2 of the posts in this section already.  How to deal with the sugaring already printed and highlighted. Great forum!
Reply:Depends on how much weld you're looking to lay down. If you have alot of weld (linear wise) I would go with the mig. Otherwise you're going to get sick of looking at the thing. If there's not alot of weld to put down then tig is a very good option. Pics of what you want to weld would help if you can get them. I own a Thermal Arc 95s. Makes a nice arc. Easy to work with. If you're just looking to do occasional tig welding on thin stuff like your evaporator pans, I think you'll be happy with it.
Reply:I don't have any pics yet, still in the decision phase, can't afford to buy these pans so attempting to make them.  If I decide to bite, I have to get the stainless and fab a custom brake.  The back pan has a series of up and down square folds to increase the surface area being heated.  That back pan alone would have about 25 feet of weld... The front pan is significantly less complex.  The real fight is picking between thin gauge for folding and thicker gauge for welding.  I was concerned about the lack of a foot pedal on the ThermalArc machine, but I've never tig welded, so don't know what I'm missing.  The vast majority of the welding would all be outside corner welding of 2 equal thickness pieces.
Reply:Hey moeh1,My offering would be to strongly suggest, since you have MIG, use that with .023/ 316 wire since it is going to be used outside. Being in a production environment most of my career, MIG is the most economical for you since you indicate you have MIG experience/equipment & you need to do multiple pieces. TIG, in experienced hands would still not be as cost-effective/productive as MIG, & in addition MIG would not give you issues with burnthru that is common with a thin metal TIG application. You would need some very serious seat time with TIG to really get efficient with metal this thin(20-22ga). Just some food-for-thought.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Originally Posted by yorkiepapHey moeh1,My offering would be to strongly suggest, since you have MIG, use that with .023/ 316 wire since it is going to be used outside. Being in a production environment most of my career, MIG is the most economical for you since you indicate you have MIG experience/equipment & you need to do multiple pieces. TIG, in experienced hands would still not be as cost-effective/productive as MIG, & in addition MIG would not give you issues with burnthru that is common with a thin metal TIG application. You would need some very serious seat time with TIG to really get efficient with metal this thin(20-22ga). Just some food-for-thought.Denny
Reply:Generally, stainless drain pains are specified to be silver soldered in the HVAC world.Rene
Reply:Hello moeh1, following the reasoning of many of the other posters here, mig might likely be the most economical way to approach this. Also, having as many of your parts formed as opposed to welding, would additionally save you a lot of head ache. If at all possible, using an aluminum backing bar/heat sink might additionally help out with warpage, puddle control, and burn-through. To help in dealing with burn-through you might consider using Solar Flux to back your joints. Also, carefully tacking(not excessively) will help, along with back-stepping or skipping around in a fashion similar to the type of technique utilized to torque engine heads. A few additional thoughts to consider. Best regards, Allanaevald
Reply:Appreciate all the advice, keep it coming!  My son is after me to get a tig so he can use it too.....The maple industry used to solder pans, got away from it due to lead in the solder, everyone went over to tig.The 25 feet of weld on one pan was after forming all the joints that could be formed - I agree not welding when it isn't necessary is the way to go.  I may get some wire and gas and try the mig this spring, at least I'll have an answer on that machine.  You mentioned 316 wire, if I got 304 or 304l SS, can I stick with 308 wire?  I have 75/25 gas, read some mixed opinions as to using it for the trial run, probably will look to get a small bottle of the right stuff.
Reply:Why not lay out the pans with tabs and silver solder as Zerepener suggested. 50 50 silver solder flows around 1350 degrees F. and does not contain lead.sg
Reply:steve,I've been following the herd...everyone welds them.  Noboby seems to mention solder except for repair to old pans, may partially be a leftover perception issue from the lead solder days.  Many guys report that they have a tough time getting any solder to stick to the stainless, but I haven't tried it myself.The deep convoluted pans on the back would be a sheet metal challenge for me to do that with.  I wish I had a good picture to share of what they look like.  It sounds like Mig has a chance here, worth trying the easy front pan first to see how I make out.
Reply:I plan to build a drop flue, attached (if I did this right) is a pic of a raised flue to give you an idea of the complexity.  My baffles would just go down and also extend full length. Attached Images
Reply:I talked to an experienced maple syruper and he told me not to make the same mistake he did. He made his flues go down and said it was a real problem getting the syrup out of each one. I am going with raised ones in mine. I also have to learn to TIG weld mine. Good luck.  We do have a wealth of knowledge here on the web.
Reply:Welderskelter, I also sent you a PM.  Folks are split between drop and raised flue.  Raised require a bit more care is getting the arch bricked up to get the heat in the flues, while the dropped have to be drained when you are done unless you also plumb in a drain line.  The raised flue also requires the use of a flow box that I was hoping not to address right away.... Either way it alot of welding.I am convinced a small tig would be a big help for tacking everything to get a perfect fit for welding, I am going to give the mig a try for the long seams.  Probably a good late spring/summer job when I can enjoy a beer after some welding.  Appreciate the inputs!