Mig verses Tig for sheet metal

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Hello all,I stumbled across this forum while researching how to do better welds while restoring my 68 Camaro. I am having the hardest time doing decent welds on the thin body panels. I borrowed a friends Lincoln WelkPak 100 flux core welder. While I can weld pretty decent on thicker mild steel, I frequently blow through on the thin sheet metal and spend hours welding, grinding, welding, grinding, welding, grinding, welding, grinding, welding, grind...... I'm sure you get the point!  I purchased the Lincoln gas kit with a .023 wire and that helped, but not much.I'm wondering if it's me or the machine. I've literally been out there for hours and hours doing this trying a multitude of things and it's driving me nuts. On all those TV programs (American Chopper, Monster Garage, etc) it seems they're always using a Tig welder.I don't mind dropping $1-2K for a Tig setup if I'll truly see better results.All of your opinions will be greatly appreciated.Denny
Reply:MIG is better for sheet, although if you practice enough it can be done well with TIG. A word of warning, it takes tons of practice to be able to do it with TIG.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:My Miller 140 dose great on the thin stuff. Smallest wire with the lowest voltage you can go while still holding a constant arcTrailblazer 302 AirpakDynasty 200 DX  Thermal Dynamics Cutmaster 52 CamoMiller Dailarc 250 OLD But great!!2 Miller 140's w/autoset NEW! Millwauke Cold cut sawsDewalt portabandJd2 notcherPipe beveling machine
Reply:Wow, two replies already, thanks guys..Do you think the mig that I'm using could be the problem? I think this is the cheapest welder Lincoln makes (could be wrong).For heat I have settings A-D. A doesn't seem hot enough and I lose arc and B seems to hot and I punch through. Do the bigger 220-240volt Migs hold an arc better especially at a lower setting?What setting should I set the gas gauge to. I've been keeping it around 15.Thank you again. I was really feeling like I was ruining this car and had to stop to do research. Perhaps I just need to stop the research and practice, but for my own sanity I need to know if it's possible the welder could be part of the problem. Thanks again,Denny
Reply:I am a rank newbie, but trolling these posts and what I learned in a course is that straight CO2 gives a hotter, deeper welds, OK for lots of things, but Argon/CO2 (75/25%) gives better results with thinner (clean) stuff. I also read about a couple of wires for bodywork, Easygrind and 20Guage - haven't tried them myself. Also anti-heat compound to pack around the welds helps keep warpage down. Let us know, I'm getting ready to weld a roof back on a '68 Fargo van. Good luck!
Reply:Stay away from fluxcore on body panels.. Floors.. frames ok but not on body panels..Not if you want them to last without paint issues..Flux eats the paint from the inside out... Here we go again.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Try to manaully pulse when your welding on really thin sheet. Try about 1 pulse per second or a little faster.If you're blowing through while trying to weld continuously then pulsing will help keep the heat buildup in check and allow you to weld longer sections.- Paulhttp://all-a-cart.comWelding Cart Kits and accessories
Reply:If you're willing to spend $2K on a TIG to get better results, you might first want to drop a mere $500 on a nice MIG machine.  The job you describe is done more often with MIG in autobody shops all across the world.You didn't say what gas you were using, but C-25 is the best for this job, and definitely stay away from the flux-cored stuff.  The .023" was the right tool for the job.  It should have been a night/day difference.  You need to see why that machine isn't doing it.Also, take a piece of copper BEHIND the weld.  It will prevent the blowout and pull heat away.  You can make copper "spoons" by flattening out some copper pipe pieces.
Reply:Zap buddy, you quack me up!!! I was reading your post thinkin' to myself "self, here we go again" and then scrolled down and saw you said the same thing. I love this stuff!!  ..........oh, jokes54321, you said something about sanity? You are here, so you just might as well take sanity out of the equation---
Reply:I hope you're not trying to BUTT weld those Camaro patch panels   If at all possible, use a flanging tool and then lap weld it.  And screw everything tight with Tek screws.Also, if you're doing rust repair, make sure you grind back to sound metal.  Thin rusty stuff is impossible to weld properly.I'm not familiar with that model Lincoln you borrowed, but any decent mig welder will have both wire speed (amps) and voltage controls.  Having the voltage set too high will give a forceful arc and a tendency to burn through.Last edited by 69 chevy; 04-04-2007 at 08:47 AM.WeldingWeb forum--now more sophomoric banter than anything else!
Reply:another noob chiming in...can you describe "copper spoons" in more detail - i think they are for heat dissipation - how do you make them? how do you use them?"flanging tool and lap weld it. and screw...with Tek screws" - can you please elaborate - what exactly does a flanging tool do - what is the need for the application here? - why is a lap weld preferrable (speaking of which, what is the correct technique for a good lap weld? - and how do the screws come in to play - to hold things together for the weld? and then they come out and holes are filled? - thanks!
Reply:The Lincoln weldpak 100 is goint to be fine for sheetmetal. Turn it all the way down, and weld away. You will have to tack the replacement peice all the way around then do very small sections of bead at a time, 1/4-3/4" at a time, alternating sides of the patch panel to avoid heat build-up and burn through. My brother bought a '57 For Fairlane that had to have alost every single panel replaced, I managed the whole project with my weldpack 100.Definitly go pick up some spare sheet metal for practice, but you should be able to get the hang of it pretty quickly.
Reply:Zap buddy, you quack me up!!! I was reading your post thinkin' to myself "self, here we go again" and then scrolled down and saw you said the same thing. I love this stuff!!
Reply:This is some great information, thank you for responding to my post. I did buy one of those cheap flanging tools at Harbor Freight and tried doing a flange, but it was a pretty wavy looking flange. Perhaps that's another one of those "practice makes perfect" things. So, I am sad to say I did do a couple of butt welds on the firewall. As the paint comes off (DA sander) it's looking like I might be replacing the rear quarter panels, or portions of them.I appreciate the valuable information you have given me. I'm not familiar with these tek screws either. Are they something I can pick up at the local welding supply store? If so I'll look for them when I go buy one of those auto darkening hoods.Thanks,Denny
Reply:TEKS screws are self-drilling, self-tapping screws.  It's a brand name, like Q-Tip, so you won't see that term on the boxes of other brands, but you'll recognize them when you see them.  You've probably seen them before.  They sell them at most any hardware store these days, including a good selection at Home Depot.  They probably even have some at Wal-Mart.A copper "spoon" is for two things.  It dissipates heat very well, but also will not weld to the steel, so if you get a blow through, or you are trying to fill an existing hole, the copper will hold the steel in place without sticking to it.  You just clamp the piece of copper behind the area you are going to weld.The other suggestion is the other important one: manually pulse the trigger make a series of spot-welds.  It will minimize the heat input and this isn't a job where penetration is the problem.
Reply:jokes, did you change the polarity of the machine when going from flux core to solid wire?????my centuy 110 has to have the polarity revesed to weld properly with solid wire & gas.....Just a thought Shawn
Reply:Hey jokes54321,I do restoration on 6-15 classic cars a year, replacing floorpans, trunkpans, kick panels, and body panels & fenderwells. Auto metal is like paper...thin to thinner. For all the panel work & thin sheetmetal, I MIG all with my Miller Sidekick 90A welder and it works superb. As the others have said, the best method is to tack every 1.5-2", and when ready to apply the finish beads, use a backing plate for support and to eliminate burn-thru. I have pieces of aluminum of different lengths, 1/8" X 1.5"W, I use because I can gently bend it to contour with the panel. It takes practice and patience to get proficient with doing auto panels. I started doing these a couple years ago when a classic car owner approached me and asked if I would be interested. Said he couldn't find anyone who wanted to do auto panels because of the thinness of the sheetmetal. So, I got started. Did a lot of practice with sheet scrap to get the optimum settings and weld beads. I use ER70S-6, C25(75AR/25CO2) @ 15CFH and my Sidekick on heat setting #2 and wire speed on 4.5. Works perfectly for the panels. I make some fine money doing these cars, and once the word gets out that you are good, you'll get quite a bit of work. BTW, learn and practice to weld lying on your back under a car.....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."