TIG using mig wire

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I was wondering if there was any reason I couldn't use mig wire for small sheet matal tig jobs.  I got Habor Fright DC invertor with a air cooled torch and have several rolls of mig wire from my powermig200.  I'd be a liar if I told you what mig wire I have without looking, but what kind of wire/rod do I need to TIG stainless?
Reply:Stainless tig or mig wire 308 is good for stainless to stainless. If you were to weld steel to stainless then a 309 is used. Nothing wrong with using steel mig wire for tigging steel.J P Streets Welding LLC
Reply:It really help when a small bead is required, but filler is needed.I like to use .035" SS wire when TIG welding sheetmetal.  Poor fitup requires that some filler be used, but the normal 1/16" filer is just too large.
Reply:For 301, 302, 302B, & 304, use 308 filler.  For 304L use 308L. For 305, use 308 or 310.  For 308, use 308.  For 309 and 309S, use 309.  For 310, 310S, use 310.For 314, use 310 or 312.  For 316, use 316.  For 316L use 316L.  For 317, use 317.  For 321, use 347.  For 330, use 330.For 347, use 347.  for 348, use 347 or 348.  Now we get into the high carbon stainlesses.  For 403, 410 or 414, use 410, 309 or 310. For 420, use 410 or 420.  For 431  use 430, 309 or 310.  For 501 or 502, use 502.  for 405 or 430, use 430, 309 or 310.  For 442 or 446, use 309 or 310.Whew!  Remember, there'll be a test on this  tommorrow!
Reply:OP, that only helps when you know what the parent metal  is.Will metalurgy and how to determine what stainless you're trying to weld also be on the dang test?Appreciation Gains You Recognition-
Reply:That's true.  It's tough to sort 'em out without manufacturer specs.  For the majority of the CRES stuff folks deal with, 308 is a fairly safe bet.For aluminum, I use a conductivity checker which gives IACS (International Annealed Copper Scale) readouts.  It's reasonably accurate, at least to sort out the weldable alloys from the non-weldable ones.For titanium. I use the grinding wheel test.  If I get a spectacular shower of white sparks, it's titanium.    Now let's see -- is it 6AL4V or commercially pure ---hmmm.......
Reply:OlPilot,Do you have a source for the conductivity meter?  Sounds like a smart thing to have in the kit!Bob Sigmon
Reply:Bob, I'll have to check with our NDT department next week.  I usually borrow one from them.  There are or were several brands available, but I'm not sure what's current.  They are small and usually battery operated.Some years back, I had a problem horizontal stack loading LD-3 belly containers in DC-10's.  (These birds can be stack loaded.  With only two inches of vertical clearance, the overhead restraint is the main deck floor beams with the belly floor locks providing fore-aft restraint.)  After loading two side-by-side sticks of five LD-3's each forward, we couldn't erect the floor locks behind them because the horizontal stack was too long and partially covered the locks.  Didn't happen all the time, but enough to be a problem.How the hell was that stack growing?  Finally, I had some empty containers flipped over and checked the bases with a conductivity checker.  Turned out the container vendor has substituted 5052 for 7075.  Running over the rollers in our Hubs, the aircraft loaders and in the bellies, the softer 5052 had literally extruded and grown enough that we could no longer get the floor locks up behind a horizontal stack of five.  We got warranty of course and it was a pain to cull them all.  But the conductivity checker paid for itself that day.
Reply:I've used MIG wire before, just follow normal rules for filler compatability.learn from others mistakes, you won't live long enough to make them all yourself
Reply:How do you straighten the dang wire out.  I'm trying to straighten some .035 stainless wire and its very time consuming.  I tried stretching it, and that probably takes an enormous force.  I pulled with vice grips and the wire snapped, but the finished product was not straight.
Reply:Without using a straightening device, basicly an oversized dinner fork you draw the wire thru, the wire ain't going to straighten.You'll be much better off feeding the wire thru a piece of tubing a few inches long just before dipping it into the pool.Appreciation Gains You Recognition-
Reply:I've found I improved my success in straightening the stainless mig wire by keeping it on the roll until straightened.  The tight roll keeps the wire from rotating while I counterbend it an inch or two at a time, working a few inches just off the spool.  Keeping it in the box and poking it out thru a hole is an even better idea, but dont let go of the end or it will pull back in and make a loose mess!!!!  First attempt I was cutting off 24" of it then trying to work it.  Bad idea.  Couldn't control the wire.  My biggest problems are stemming from the inability to quickly and consistently feed filler into the puddle and I need straight wire to work fast on some relatively tiny joints (3/4" square tubing).  I may buy some 1/16 filler rod and see how that works on the 1/16 tubing.