As always think thru your goals vs the cost, it would make very little sence to add optional add ons to a welder to have access to for an example a tig capability on the welder below if the upgrade if it cost more or even close to what a second welder cost

ENGINE DRIVEN ARC WELDER/ generator

http://www.mylincolnelectric.com/Catalo ... px?p=45752

TIG OPTIONS

http://www.mylincolnelectric.com/Catalo ... 000%20Plus

mig options

http://www.mylincolnelectric.com/Catalo ... 000%20Plus

at some point the cost of adding the options vs just buying the correct second welder needs to be carefully considered, but depending on your goals its sometimes a very useful option to add an upgrade kit to a welder

Always think thru your goals when you purchase equipment,the rough rule as a guide is youll need about one amp per .001 inch of material thickness to well aluminum effectively, IE youll need about 250 amps to weld 1/4" thick aluminum, now that is based on the idea of near constant use, naturally you can weld thicker material if youll allow less than a 70%-100% duty cycle, and as a general rule a 250 amp rated machine will operate at 70%-100% duty cycle at significantly reduced amps (lets say 180 amps as a guess) from its rated 250 amp max.

heres my mig

http://www.welders-direct.com/merchant2 ... ode=907321

viewtopic.php?f=60&t=157&p=891#p891

viewtopic.php?f=60&t=72

If you look around at local welding supply shops and local welding shops you will on occasion see great deals on used welders that get traded in or swapped on upgrades, a close examination will usually give you some idea as to its condition and the local dealer in that brand can give you an approximate age with its serial number and model, some welders have been used hard and constantly, but a surprising number spend a great deal of time just sitting unused in shops, I know of several shops that have several welders and most of the works being done with one or at most two welder, its not at all rare to find high amp rated mig or tig welders that have had little real use.
If your thinking of buying a shop welder Id strongly suggest a 220 volt 180-210 amp mig, or 220 volt 200-270 amp TIG will do about 90% of what most guys will ever do, if you get a MIG with a spool gun that can do aluminum, you have a rather versatile welder, but a good TIG is almost unbeatable in the versatility race, its a bit slower but it will weld almost anything, in skilled hands.
Ive purchased several used welders, and had zero problems, but I always do a few test welds before I buy, one,If you can,t do that your best off avoiding the welder. and keep in mind ,that the main things you need to do, in deciding on a welder is making sure it meets your needs and that you have the electrical capacity to run it, stick to recently built name brands so you can get parts, anything over about 10 years old is usually hard to get parts for.
and stick to single phase 110volt or 220 volt welders as most shops don,t have three phase power

http://www.usaweld.com/SearchResults.asp?Cat=25

I have not seen one yet in person but a combo , MIG/TIG/ARC welder IF its well designed has some intriguing potential, and HTP is known for building a decent quality welder, I know several guys with HTP tig welders and everyone happy with those.

STEVE POSTED THIS BIT OF INFO
"
It only welds in DCEN (Direct Current Electrode Negative) which is cool because most of your welding will be DCEN. However, don’t expect great results on aluminum which is best welded in A/C current mode.

I have a TIG and unless I am welding aluminum or stainless I will reach for my MIG welder first. I think you would be better off buying a good MIG, master that and then decide if you even need a TIG. I like having the option of the TIG but don’t really need it for the car but I have come across situations where it was the only option to restore an otherwise non-reproduction part.

If you can afford 1,200.00 for a welder, buy a GOOD MIG and then if you want a TIG go get a good one with A/C, balance and pulse.

Steve"