Re: MIG welding and advice
 

Not a lot of confusion, just different discussion from different sources. Both use an arc, both use a stable shielding gas (many times the same type of gas too), neither make use of flux due to said shielding gas, and both commonly (MIG always) use a filler material added to the arc to create strength in the weld. The book I used for my welding classes lists TIG as a GMAW process that is also known as GTAW. The more acronyms you throw in the mix the more confusing things get. Tungsten is a metal and that is where the M comes from in GMAW, so I don't feel bad about saying what I said. If the world has changed since then and dropped my views, I'm happy to change my ways.

While this thread has remained educational, it has completely derailed off topic, which is so strange for CD... :ahh:

That being said, if I was the OP I would make use of that welder and build a steel chassis. Every time we build an aluminum chassis, we swiss cheese the thing for days to make weight. Every time we build with steel we come in comfortably under weight.

Re: MIG welding and advice
 

Get the PN, call Lincoln, make sure you can use it to weld aluminum before you go through any more hassle. They will also be able to give you PNs for the appropriate equipment you'll need (spool gun, gas controller, wire, etc) Also consider keeping your welding table surface steel, it will be easier to maintain in general.

I think that if you keep your expectations realistic, you'll do fine welding aluminum. However, those realistic expectations may be no welding anything thicker than 0.093in in aluminum.

Having said that... MIG welding aluminum can be tricky. It isn't rocket surgery, but requires careful setup and very clean equipment and material. The setup chart inside the cover is a good start.

http://www.weldingtipsandtricks.com/
^IMO this is the best online resource for welding. Not exactly text book, but Jody REALLY knows his stuff and how to get it done. Pay careful attention to his MIG welding Tip series.

I think you mean to say "spool gun" as there is no such thing as a TIG "gun" only TIG torches, at least in general. It may be semantic, but these things matter.

100% Ar is suggested by many, but is not always the best shielding gas. A helium/argon mix is best for welding aluminum (TIG or MIG imo) because helium has much better heat transfer properties. This lets gas-cooled torches run cooler, and transfers more heat to the work. Both of these increase the capabilities of the welder. I like 50/50 mixtures, but even 25% helium makes a big difference. Helium also helps create a more stable MIG arc.

^ Agree 100%. Thin-walled steel (think 0.035in) can have a comparable weight to aluminum tubing of similar strength. Welding it is a helluva lot easier. Just keep some sharp drill bits (step drills are great for this) around, learn how to use riv-nuts, and don't cheap out on the hacksaw blades (Lennox bi-metal blades are the best IMO).

My qualifications on this topic:

-Formerly ASME & AWS certified TIG welder for alloy steel and aluminum
-2 years of experience developing MIG welding wave-forms (specifically for titanium), researching welding theory as well as experimentation. A lot of this effort's success was a result of understanding and implementing argon-helium mixtures.
-Taught welding for a year in college, also started and ran my colleges welding lab (BTW: I started every student off welding aluminum with 50ar/50he gas, no big deal)

Re: MIG welding and advice
 

Absolutely correct.

However I rarely do that because I have a handy propane torch to preheat if need be and my welder is getting up there in power capability.

So I was curious (it's been a while) I called AWISCO where I buy my gas and they are getting back to me about the cost difference between the custom mix of 25% Helium / 75% Argon (I bought my previous tank elsewhere and apparently this was something unusual for them) and 100% Argon.

Last I looked the cost of the mixed gasses can reach a point where the cost of savings of the machine (though a donate machine can skew this) can make more sense to buy a more powerful welder (because it's cheaper over usage). Course if your usage is really low maybe it doesn't matter.

You can get a welding gas mixer but they are not typically cheap.

Re: MIG welding and advice
 

It's true that helium is pricey, and helium prices have spiked recently. My last price out was (in round numbers) $100 for Ar and around $250 for 50/50 (special order). This was for a 300ft^3 bottle refill. FWIW I have used 50/50 and 100ar with a Lincoln Precision TIG 375, their top-end TIG machine at the time, and much preferred 50/50 for aluminum as compared to 100ar.

At work we use a gas mixer, that was a little over a grand. I'm sure one could make their own crude gas mixer for not huge amount of money though, i.e. just 50/50, not 10/90-90/10 like a high-end mixer.

Looking around on the internet, some people think 50/50 is too much helium and suggest between 25/75 down to 5/95. Last time I checked 50/50, 25/75, and 10/90 are available OTS.