i assume a 40 cf may be considered minimum decent size?

jim

The regulator that came with my Lincoln Handi-Mig is set for 20CF per hour, meaning 1 hour of actual trigger time. I started with a 20 but after the second fill upgraded to a 40. It's still small enough to be portable but large enough to give some time. Also, it usually costs almost the same to fill either size.

Jim I forget the volumes of the tanks, but I have been a little more satisfied with our larger 80? here at work as it is considered the commercial size. I've used it at home for long 914 projects and it supplied me well without running out. It is abit more to handle and move about the shop because of it's size. I also use the next size smaller 60? bottle for my Tig and it seems to need more frequent refills than I like for convience, but the bottle is much easier to handle. I own the smaller bottle and I think it cost me $200 purchased.

Here's a good chart. I got a 40 with my welder, but moved up to a K cylinder pretty quickly.

It will last half as long as a 40. I bought an 80 because it would last twice as long as a 40

There is no accurate way to tell how long. It is going to depend on how your regulator is set, leaks, etc.. I have built 2 welding carts, 3 workbenches, a brewstand, an engine stand, the shop dollies for my 914, and done the full floor pan and rear firewall of my car with no refills on my 80 cu. ft. bottle so far. I do want a small bottle as a backup for when my 80 runs out since that will happen on a weekend when the welding shop is closed.

IMHO, 80 would be the minimum you want for MIG unless you are frequently moving the welder to offsite projects.

The 80cf bottle is totally manageable on a cart and, as someone pointed out, costs only a little more to fill than the 40cf.

my local roberts oxygen quoted me $181 for full 60cf tank.

i think this is the size i will go with when i pull the trigger on getting the stuff i need to start using my mig.

I usually flow 15 cfpm [OOPs this is cu ft per hour, not minute} when tig welding inside with no breeze, and 20 when outside. . . I run a big bottle 220 cu ft so it lasts around 10 hours welding. . an it always runs out in the middle of a job. . .
I only use argon on the tig machine and run straight CO2 on the mig. . a lot cheaper and the welds are the same on steel. . last bottle I got of argon 220 cu ft was right at $130 from Praxair. . that is the commercial rate and bigger the bottle, the rate gets better

four flares and pedal area repair with a 20. set @15 at the nozzle.
Check craigslist for bottles!

be careful when buying a used bottle.... they have to be pressure tested I think every ten years ... at your cost. Plus, it may be a bottle someone was renting from a distributor and sold .... Ask me how I know.

good point.

here is a good youtube video on the topic.

http://www.youtube.com/watch?v=ndGB-Ww47M4

jim

Most places now adays just switch out bottles, they dont actually fill them up.

I have a 60 that I use. When Im welding alot itll last typically a month. Good size for my cart as well.

The cost is up front when you buy that first bottle. There's a shop locally that gets regular shipments from one of the local gas companies (Airgas, I believe). I can swap out an empty 80 on a full one for $35.

Jim, do you have any commercial customers that would allow you to buy your supplies through them? I was able to buy my welder and first tank at a discount through our facility maintenance dept and it was all delivered to me at work.

Just swapped out my 80CF cylinder today. I asked the guy at the counter and he said to expect three hours of trigger time using the 80. I am on my 3rd one for my resto, but I lost about half of a bottle because I forgot to turn the gas off once.

So, you are probably looking at about 45 min of trigger time for the 20CF. I would recommend the 80 if you have a cart.

I use an 80 tank and seem to use 4# of .023 wire per tank. Running @25

3 tanks and 13# of wire so far on the project