AC only TIG Kemppi PS2800 + TU20: Worth buying?

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Kemppi appears to be a quality product however information in the USA is extremely difficult to find.  And I can't imagine getting parts either.But I might be able to buy this rig for under $400 and am considering it.My most likely applications would be sheet steel, specifically auto body.I know AC is alum and DC, steel.  But the cleaning action of AC sounds like alum is AC only and with steel, it probably doesn't matter much.  However DC reverse might be desirable for .032" sheet.Any thoughts?
Reply:Kemmpi is a good product. Sold and mostly serviced in England. $400 is cheap if you have $400 and want a welder of that type.Arcon Workhorse 300MSPowcon 400SMTPowcon SM400 x 2Powcon SM3001968 SA200 Redface1978 SA250 DieselMiller Super 32P FeederPre 1927 American 14" High Duty LatheK&T Milwaukee 2H Horizontal MillBryan
Reply:The Big Question is What are the drawbacks of not having DC?
Reply:This is my first TIG and I'll be learning the method.  My expertise is oxy-acetylene welding auto body.  I just went from a Victor J-28 to a Smith AW1 and wish I had done this 40 years ago.
Reply:From what I gather the TU20 is an HF Tig Box, capable of AC/DC.  Do you mean the power supply is AC Only?   If you want to weld steels with tig, I'd seek out a US made DC machine and save yourself some potential service headaches!
Reply:Yes, the power supply is AC only.  (It would make a nice AC stick machine.  I have an old Miller 225 Thunderbolt with the Miller DC Rectifier Box for it.)But service means nothing to me since I'm only able to spend not even $400 really....  And for that price, an inverter (electronic) style, if it breaks, you throw it away.  So what is important is to buy a robust welder.  Kemppi is not popular but seems to be a top tier welder.  So that might be the best shot for me.Still, I'd like to hear the shortcomings of welding steel w/AC.Another comment on welding auto sheet metal.  I'm only just starting MIG and curious about TIG.  But a recent trip to a local world-class custom car builder laughed and said no one welds anymore.  Glue is the new method.  Then my auto parts store manager said he hardly sells any Duraglass or Tiger Hair (bondos) since its all panel replacment insurance work - and now glue is more popular for that task.But then, I'm only interested in doing old cars...
Reply:Originally Posted by Cardinal GrammeterYes, the power supply is AC only.  (It would make a nice AC stick machine.  I have an old Miller 225 Thunderbolt with the Miller DC Rectifier Box for it.)But service means nothing to me since I'm only able to spend not even $400 really....  And for that price, an inverter (electronic) style, if it breaks, you throw it away.  So what is important is to buy a robust welder.  Kemppi is not popular but seems to be a top tier welder.  So that might be the best shot for me.Still, I'd like to hear the shortcomings of welding steel w/AC.Another comment on welding auto sheet metal.  I'm only just starting MIG and curious about TIG.  But a recent trip to a local world-class custom car builder laughed and said no one welds anymore.  Glue is the new method.  Then my auto parts store manager said he hardly sells any Duraglass or Tiger Hair (bondos) since its all panel replacment insurance work - and now glue is more popular for that task.But then, I'm only interested in doing old cars...
Reply:Originally Posted by Cardinal GrammeterStill, I'd like to hear the shortcomings of welding steel w/AC.
Reply:The Kemppi is a turn key rig complete with torch/consumables and foot pedal.
Reply:If you have the option here to buy an AC only tig inverter for $400,  GO FOR IT.  You have the opposite problem of most.  Adding AC to the tig equation is what gets things pricey.  You could pic up another DC only machine in the future, but if you're all setup for tig, just rig your Tbolt for a DC scratch start.  A pedal and HF are luxuries for DC tig welding.  Unlike AC, they aren't mandatory.  You can totally get by with scratch start and no remote amperage control.  I am far from a great tig welder, but I can totally get by with scratch start and make good looking strong beads.  Unlike aluminum, you don't need to lower the amperage as the piece heats up because steels not as good of a heat conductor as aluminum is.  As for playing with old cars, MIG is what you want for 99% of the projects that will arise.Last edited by Drf255; 05-18-2014 at 06:17 AM.
Reply:I even have an old Montgomery Wards HF box for DIY TIG on a AC stick machine.  It has a tig torch head you clamp in the stick holder like a fat welding rod (!)  Comment on MIG, I've used silicon bronze wire and it is amazing the reduced distortion!Now I'm pretty much decided to use Lord's Fusor structural glue to patch the 74 Datsun pickup core support.Like you say, I probably don't need a TIG machine for what I'm doing.  My only thought is that the Butt Weld is the Gold Standard of rust fighting joints in auto body while the Spot Weld is the worst along with the Lap Joint.  The interesting thing about the adhesives is that the completely seal the Lap Joints eliminating the capillary action which draws water and rusts out.So its like GLUE and BUTT welds for the best anti-rust.MIG Butt Welds are very difficult - the O/A torch is many times faster although with lots of distortion to manage.MY BIG QUESTION:  Would TIG do the Butt Welds faster than MIG?  While the distortion would be less than O/A, you cannot mange it - you're stuck with it.On managing O/A distortion:  You preheat a "tension ring" around where you are welding so you don't produce compressive yielding at the puddle which results in residual tension at the weld and hence distortion.  One you get skilled enough to do this, when the weld cools down, the weld and surrounding metal return to their proper position without distortion.  It is an elegant process which requires ridiculous amounts of judgement, intuition, and skill.This works if you are in a flat-ish section.  If there are corners/bends nearby, it compounds the problem massively.So if you really don't need the full strength of a Butt Weld (which a Spot Weld doesn't even come close), GLUE might be pretty good.  Let's face it, the OE are using it more and more.
Reply:Originally Posted by Cardinal GrammeterBut I might be able to buy this rig for under $400 and am considering it.My most likely applications would be sheet steel, specifically auto body.
Reply:Turns out the PS2800 is a DC unit!This actually changes things.  From what I can tell, there is really no need for an AC stick welder - especially where steel and aluminum are concerned.  The 2800 is a pretty high current DC source (I think its around 300 amps) and might be worth having just for itself.  (If I'm wrong abound needed AC, please someone let me know.)Of course a TIG that won't weld aluminum is a real negative.Was just thinking that the 2800 has the bridge rectifier in it - I wonder if AC output is nothing more than tapping in before the rectifier???