How much welding can be accomplished with one tank:
http://www.tractorsupply.com/webapp/wcs/stores/servlet/ProductDisplay_10551_10001_36248_-1______?rFlag=true&cFlag=1

Kind of a tough question, but if I were to put it in terms of a quarter panel skin, which leaves you with a seam almost 4 ft all along the length of the panel, I would expect a 20 cu ft bottle to last through a couple of those. In the case of welding sheet metal panels we're just making a series of momentary tack welds, not running beads as if we were doing a frame, trailer, etc. Running beads will eat up the gas quickly whereas making stitches of tack welds does not.
Sorry if this is vague...hope it helps!

Oh...and fwiw I don't use anything smaller than a 40 on my mig (75/25 mix) so that I don't have to refill as often.
Tom

just to liven up the how fast it goes equation ...... when you start doing certified tube welding you not only have a gas shield on the Arc side but you purge the inside of the tube also ....... :D

Tom, that helps a lot as I will only be welding sheet metal. Thanks.

:thumbsup:
Funny...just yesterday something came up around the house requiring me to weld up some stainless steel. Now I have to get a small bottle of tri-mix shielding gas! Fortunately the guy at the welding supply is a friend so he'll loan me a "demo" spool of wire and only charge me $20 for the bottle. ;)

I bought a 50 cf bottle from a local welding house for 150 bucks and it was aluminum so it is super light. I havent done enough to use much of the gas yet, which is a 75/25 mix snd cost 29 bucks to fill, so I cant tell how long it will last but it seems like it will last pretty long.

Tim

My main problem was the solenoid valve that controls the flow of gas. It started to leak gas and the bottle pressure started to nose dive in a hurry. Something to keep an eye on because even a small leak can waste a lot of gas. Always shut the bottle off when not in use, for the same reason. My projects aren't usually big, so I can hardly remember when I filled the bottle last. The mig sure is handy when you need it though.

I bought that very 20 cf bottle ( baby bottle) from Tractor Supply. When it ran out (very quickly) I took it to my local welding supply place ( nipple and all ) and traded up to a 40 cf bottle. The extra trips/running out etc. wouldn't be worth the savings on the smaller bottle. I would in hindsight go even bigger yet. As an example if you had your regulator set at 20 cfh you would be able to hold the trigger down continuous for 1 hour before running the 20 cf bottle empty.

Tractor Supply seems to sell almost empty bottles.
The last two I bought from ran out very quickly.

I have a 50cf and a 20cf, nice to have a backup when you run out on a Saturday evening. Prices around here are getting ridiculous, though. Last time I took both bottles to refill, they cost me $120. The time before that, both bottles cost me around $60 to refill. :sad: