welder upgrade advice

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Hi, new member to the forums, first post, but I have read things on there on and off for a year or so... I've spent the last couple of days reading and searching, and I'm only getting more and more confused, so at the risk of being told to use the search function (which I did)....My hobby is car restoration, and 95% of my welding is on thin gauge body work, with maybe another 5% on thicker frame members, maybe a roll cage or two... The thickest stock I would think I'd need to weld ever is probably 3/16"...I picked up a cheap Harbor Freight dual mig 151 (220v) - mostly cause it was cheap (80 bucks). I'm running .25 wire, and argon/co2 75/25% mix. It does not have the capacitor mod, or anything else changed on it.I have no problems running good welds when overlapping the sheetmetal, or when using  a copper plate backing (setting is usually min-2, wire speed around 4, min-1 just gets me no penetration)... but I really want to improve further and do proper butt welds, when there is no backing. However, no matter what I try - I cannot get it to work - I always get burn-through. I'm not sure if it's me, or the machine - probably a bit of both... I'm considering upgrading to a better machine, to at least rule out one of those possible causes... I don't think I'm ready for TIG just yet, so sticking to MIG...so, some questions...1. For welding 18 and 24 gauge steel sheet - is my wire size and shielding gas the correct choice?2. Has anyone had luck in doing consistent butt welds in sheet metal without burntrough using a HF welder like mine, or is that a pipe dream...3. I think I prefer having the extra oomph of a 220v welder, so I'm considering lincoln/miller/hobart machines in that range. However, if I'm going to be doing mostly thin sheetmetal - should I just get a 110v, and keep the cheap 220v HF for the thicker stuff? Are the 220v machines capable to be dialed down enough to work on thin metal?4. I am looking at a 5-6 year old Lincoln 255 on craigslist, or a millermatic 210 (same age). Sold by a shop that used to do fabrication, the torches are missing, everything else is there. Price is $700. Are either one of those two something that will fit my needs, and is the price right?5. Any other recommendations on what machine I should be looking at? The Millermatic 211 (dual 110/220v input) seems to get some good reviews here, is that a good option?
Reply:Originally Posted by jordankso, some questions...1. For welding 18 and 24 gauge steel sheet - is my wire size and shielding gas the correct choice?2. Has anyone had luck in doing consistent butt welds in sheet metal without burntrough using a HF welder like mine, or is that a pipe dream...3. I think I prefer having the extra oomph of a 220v welder, so I'm considering lincoln/miller/hobart machines in that range. However, if I'm going to be doing mostly thin sheetmetal - should I just get a 110v, and keep the cheap 220v HF for the thicker stuff? Are the 220v machines capable to be dialed down enough to work on thin metal?4. I am looking at a 5-6 year old Lincoln 255 on craigslist, or a millermatic 210 (same age). Sold by a shop that used to do fabrication, the torches are missing, everything else is there. Price is $700. Are either one of those two something that will fit my needs, and is the price right?5. Any other recommendations on what machine I should be looking at? The Millermatic 211 (dual 110/220v input) seems to get some good reviews here, is that a good option?
Reply:Originally Posted by norite1.Your gas and wire size are the best choice for welding steel sheet metal.2. I have a MM200 so can't comment on the HF but to do butt welds, fit up (minimal gap) is necessary.  Proper voltage and wire speed are critical.  If all else fails pulse the trigger on the gun so you are basically putting in a series of spot welds.  Keep the panel cool with a wet rag or spray bottle to minimize distortion.3.  I am in the 240V camp unless you need to often move your welder around to different sites and do light jobs..  The 240V machines should be able to weld at the low end as well or better than the 120V machines as they usually have more sophisticated controls and better feeders.  Of course they are better at their high end which exceeds the capability of the 120V units and may offer more options and features such as pulse, spray or spoolgun connectivity.4.,5. I'll let someone with experience with these newer migs comment on this.  I'm looking for a wirefeeder for my Lincoln V350 Pro for big fluxcore, but I will keep my MM200 around for smaller stuff.
Reply:Originally Posted by jbmprodsthe price on the 255 is not to bad for that unit if it had a gun and it was owed by a private person. but since it was used in commercial fab for 5+ yrs i myself would opt for the new mm211 for a few extra bucks.....jim
Reply:thanks for the replies!Sounds like the MM211 might be the better option, and I do like the dual voltage capability... $1000 is at the very top of my price range, but I do consider this as a longer term investment, so I should be able to convince my wife ;-)... Time to start looking for one...
Reply:On a side note, I'm somewhat a beginner and started out picking up an HF mig welder, plus did the cap mod.  At the same time I was taking a welding class at a local community college and I could do decent welds on the Hobart's they had, but with the HF I was often burning through something because if felt like the welds just were not sticking, and all in all it didn't work that well.I ended up picking up a MM211 after a while and don't regret it a bit.  I will not say my welds are always perfect and I don't still burn through something now and then, but all in all I can still lay down some pretty acceptable welds.
Reply:Originally Posted by jordankthanks for the replies!Sounds like the MM211 might be the better option, and I do like the dual voltage capability... $1000 is at the very top of my price range, but I do consider this as a longer term investment, so I should be able to convince my wife ;-)... Time to start looking for one...
Reply:Just a question for the experienced welders here. What if he stepped down to .023 wire size? Wouldn't that help control burn through? I recently picked up a spool of .023 to try on thin wall pipe that was left over from a dog kennel.
Reply:Originally Posted by papaharley03Just a question for the experienced welders here. What if he stepped down to .023 wire size? Wouldn't that help control burn through? I recently picked up a spool of .023 to try on thin wall pipe that was left over from a dog kennel.
Reply:Originally Posted by Boostinjdm.023/.025   same thing.