I'm about to put a '75 in the air that's been sitting in my garage for a year. This will be my first crack at rust repair. The Hell hole and lower long area is where the most attention is needed.
I'm new to welding, I've picked up so much information here I feel pretty good about starting this.
I picked up a Lincoln 3200HD off craigslist for $200. I've got a regulator, now I need a cylinder. What size should I get? I was looking at a 20lb bottle available on craigslist. It was designated as CO2. Is that the right bottle? Can it be filled with mix gas? Should I get something bigger?
Tips. tricks, comments, suggestions?
Thanks

I have a similar welder and I got the 40CF. It last pretty long, but I had to refill a couple times already.
Places will exchange tanks on fills unless you wait for "your" tank be filled.

I got mine off ebay - if you can't find one on craigslist. I was good quality, but it didn't matter once exchanged.

Buy the biggest bottle you can afford -
The cost difference to refill is minimal, and if you go
with a small bottle, you will run out on a saturday afternoon, and
not be able to exchange until the following Monday. Left with a whole weekend of
welding to complete, and no way to get it done...

just my .02 -

TE

I believe that the bottle has to be bought from the company (welding supply shop) where you are planning on exchanging it.

It's kind of like those Rhino propane bottles. You "buy" the initial one and then from that point on just exchange it for a full one when it gets low. (you can exchange up to a larger one at a latter date)

I live in L.A. and I don't think there is anywhere that will re-fill a bottle from an "un-known" source.

The fact that the bottle you are talking about is marked as for CO2 would bother me (and I think the welding supply shop). I doubt you could use it when you want to get a different mixture. In other words, once a bottle has been used for CO2, they wouldn't allow you to use it for an Argon/CO2 mix.

Before buying anything more (or totally trust me), go to your local welding supply shop and ask them.

Wes Vann

If you are going to use CO2 then a smaller bottle will suffice as CO2 is in liquid form and you are actually pulling the 'evaporated gas' of the top of the liquid. Through that process it will last a long time. You can not use a CO2 cylinder for mixed gas as it has a different valve. You should be able to buy either of the smaller bottles and exchange them at any store - only when you get to the larger cylinders do they become difficult to exchange as most company's only rent not sell the larger tanks.

CO2 will work a little better then flux core wire. If you are welding outdoors then flux core will work no matter the wind conditions. CO2 is cheap and will last a long time Vs. mixed gas which is more expensive but gives a significantly cleaner weld with less cleanup needed afterwords.

Hope this helps

Different categories of gas have different threads. CO2 and CO2/Argon both use the same threads, so there should be no problem. You cannot, for example, fill an O2 bottle with CO2. If the bottle is more than 5 years old, you will need to have it tested before anyone will fill it. The easy answer to that is to simply swap it for a filled bottle, and the gas supplier will take care of the testing before they swap it to the next customer. I've swapped several different gas bottles, and nobody has ever checked where I got the bottle.

Don't waste money on a shiny brand new bottle. As soon as you swap it, it is gone. You can have your bottle filled, but you'll really appreciate the convenience of swapping.

The Blue Rhino propane cylinders have a proprietary valve that can only be refilled by Blue Rhino. That's why they are so expensive - they already have your pants around your ankles.

I bought the 70 cf one. The small ones have a habit of running out at the worst possible time. I bought the bottle from the same place I get it filled at. At swap time there are no questions asked.

Are you sure? I was under the impression that the CGA-580 valve was used for argon, helium, nitrogen, CO2 and non-flammable mixtures.

Bought the 80 cubic foot tank from a place in Jersey that advertise on the web as www.cyberweld.com.

Free shipping and I had the bottle filled by them. I've had it filled once already by a place here called AirGas. They tried to do the we'll-take-your-bottle-and-give-you-a-different-filled-bottle thing but I insisted that they fill my bottle. To fill mine, I had to stop back later.

As someone mentioned before, the probability of running out of gas when you're welding is inversely proportional to the size of the tank. Get the biggest one you can get.

True - 80cf will last 2xs a 40cf...but,
that lincoln 3200 is a nice portable ~115v welder and if you move the machine around alot, a 40cf plenty and easier to carry. If you're going to mainly stick it in the corner, go for a bigger tank.

My bad - same valve on mixed gas and co2. It is the CGA540

I have a 234cf Nitrogen cylinder that I hope to use for MIG gas. Way too big, but the price was right. I might see if I can trade down to a smaller size. I'm getting a MIG for Christmas.

I bought the small one and it lasted for an hour of welding....

2 refills and I upgraded to the bigger bottle....

Ken