Mig gas bottle.

[m_c]

The small gas bottles can be a bit of minefield.
Some use larger bottles at lower pressures, and some use smaller bottles at higher pressures.
Have a search on ebay, as I was surprised at how many suppliers there are when I was considering cancelling the contract for the full size bottle.


As for insurance, having a bottle of LPG in your garage is far more high risk, than a bottle of inert gas that in the worst case scenario might blow the top of the bottle. It's oxy-actylene that insurance companies don't like. One bottle that will go bang and take of skywards with no warning if you do something wrong, and one that'll sit gradually heating up until it ruptures and flatten everything within quite a large radius if you get it wrong, it's pretty easy to understand why insurance companies don't like them.

[birchy]

Probably a bit late, but I'm a C&G qualified welder. For home-use MIG, I use CO2 without any problems at all. A lot of people say "don't use CO2, too much spatter, etc" but you'll find that 99% of them have never tried it! You will get better penetration with CO2 than Argoshield and only need around 5LPM gas flow. I used to work for one of Europe's largest steel fabrication companies and we used nothing but CO2 about 20 years ago. For home use, you can get CO2 from any gas supplier (or a friendly pub landlord!). I paid £10 for a 9L bottle about 5 years ago. The other option is to get Argoshield from an Adams Gas outlet. I've recently got a 9L bottle of pure argon for my TIG set. It was something like £55 deposit on the bottle and £50 for a refill. Personally, I will not pay bottle rental because these little blighters last for years and I do quite a lot of welding.

[Musht]

>>"don't use CO2, too much spatter, etc" but you'll find that 99% of them have never tried it!

I must be a 1%er then.

My EXPERIENCE , as an inexperienced amateur welder is that aron mixes are a lot easier, as an experienced weleder your mileage may and probably does vary

MIG Welding Gas Comparison

[birchy]

I guess experience does help, but I don't find differences in using CO2 or Argoshield, other than CO2 is cheaper and gives better penetration. The main downside of CO2 vs Argon mixes is that CO2 can freeze the regulator under heavy use, especially if gas flow is set too high. I suppose gas quality also varies from supplier to supplier and I dunno what those disposables are like....pretty poor I would imagine.
EDIT: I just remembered a conversation I had a few years ago about CO2 quality. The basic conclusion was that "pub gas" CO2 has better purity than fire extinguisher or welding gas because it is "food grade". Whether there's any truth in that, I really don't know. I've only ever used "pub" CO2 bottles on my home welder.

I did take a look at the link posted above, but didn't read beyond the first few lines:

All welds were made in the same hour with the same welder settings

You cannot simply turn the machine on and change the gas without changing settings! No matter how experienced someone is at welding, they'll never produce a decent weld if the machine isn't set up correctly. Every single job needs to be set up to suit the materials being used. Even the gas flow may need to be adjusted as it DOES affect the weld finish. Too much gas flow can be as bad as too little. Another big pitfall of home users is that they buy cheap equipment like those Chinese things or the low powered sets like the Clarke 100A which aren't much good for anything other than tacking sheet metal. Personally, I'd never buy a welder with less than 160A, with 200A being preferred if you can afford it. It's basically down to duty cycles and having plenty of head room so you're not running flat-out all the time. I bought an Oxford 180A mig nearly 20 years ago and have used approx 8 or 9 15Kg spools of 0.8mm wire in that time. The only maintenance I've had to do is blow the dust out a couple of times and replace the gas shroud and a few tips. On certain things, it doesn't pay to buy cheap.

[Web Goblin]

I have had a go at repairing a couple of the clark type migs and boy are they crap. Personally I have a Sterling mig which has hardly been used and a Pico 140 inverter which is a great little machine. I think some of the newer inverters will go to 160 amp will running off a 13 amp plug but you wont get much more than that but I wouldnt fancy trying to run it at a high duty cycle or it will probably cook the plug never mind blowing the fuse. I think that is the main reason why people go for the small cheap kits is that they can run them from a 13 amp plug for a while.
We have a load of old Murex 500s at work that will be at least 20 years old and still give a great weld. They dont look very good but do the job.

[birchy]

I run my Oxford off a 13A socket but it does take the MCB out at top end, so I fitted it to a spur and used a 16A C rated MCB. It still has a 13A fuse in the plug. Or at least I *think* it does. Haven't had the plug top off for at least 10 years! The beauty of these old Victorian houses is that the cellar has become my workshop and the now disused "back room" chimney has an extractor fan fitted into it, so all my welding smoke is cleared within seconds.

Those Murex lumps need a crane to move them about but they last forever. The production place I used to work at was running them at 300A+ all day, every day (and sometimes all night too!) and they were about 15 years old and still going strong when I left 10 years ago. They're probably still using them now.

[Web Goblin]

Yeah the old Murex machines will outlast the newer stuff easily. The thing that gets me is the price and complexity of the new inverter type welders compaired to the older thyristor bridge type. They cost a severe amount more that the old ones, are a pain in the arse to fix but do they really give a better weld?

[m_c]

co2 isn't as good for mig as a proper argon/co2/o mix, however it does work well enough for lots of applications.
Pure co2 does create a hotter weld, however that can be a problem if dealing with thin metal.

The main benefit of the proper mix, is it has a trace of oxygen (2% IIRC), which helps burn of impurities.
Ideally you should have all metal ground clean, and free of oil, but that's not always possible.
With pure co2, any impurities can cause excessive splatter/porous welds, whereas a proper mix is a bit more tolerant and minor impurities will burn out into the flux instead of affecting the weld.

And for the benefits of Birchy, I also have a bit paper that says I can weld. Having a bit paper that says you can weld 6mm bits of plate in designated ways, doesn't mean you can weld, as was demonstarted by some of the numpties who managed to pass the course the same time as me.

[Web Goblin]

We have two guys at work who are the best welders I have ever seen. Can weld all day long. Ones called Robot 1 and the other Robot 2. Dont know what their qualifications are though

Sorry couldnt resist.

[m_c]

If only they could develop a robot that can handle patching back together rusted to nothing metal, along with straightening out and welding back together deformed metal...