I learnt to MIG weld last year and I thought id have a go at ARC as well. My 90amp MIG is fine for doing my mini etc but I fancy a cheapish arc for gates/few other projects
What AMP's is needed for arc welding 4-5mm mild steel? And what size Rods as well?
Something around 140A would handle 3.2mm rods ok, go up to about 180A and you could use 4mm ones. I think most of the pro's on here tend to use 2.5mm rods a lot, doing multi-pass runs and/or weaves where needed. An arc welder can handle some pretty thick stuff compared to a mig amp for amp so 4-5mm should be a breeze for even a smallish machine. I'll also add that most arc welders are AC (buzzboxes) and most inverter machines are DC, DC gives a much smoother arc than AC but at the sacrifice of a little penetration I believe. I have some rods that are a pain to strike on AC but work a treat on DC. Don't forget that the bigger the machine, the higher the duty cycle on a given rod size. Also, the duty cycle on inverters is usually higher than transformer machines of the same output.
Hope this helps?
Webba, all advice so far is good (glad to see you've been paying attention Woz). Whatever amps you use will relate to the rod size and type, not the metal to be welded. As Woz says, a 140A set will run 3.2's, but if it's a transformer, not for long. It will run 3.2's all day. The cheapest way to do what you want is to buy any old 140A transformer (buzz box), and some decent quality 2.5mm 6013 rods (so don't get them from machine mart). The beauty of arc is that the penetration is good on any size material, so you can do multiple runs (stringers - eg long straight welds, no weave) with small rods. Just as good as using big amp migs.It's cheaper, but takes much longer though. If you're not paying wages/earning, then that doesn't matter!
As said, DC is much easier for positional work.....and certain rods, the main problem is arc wonder (you build a magnetic field) but unless you getting above 250amps it ain't ever gonna be an issue....... whats your budget??, if you can afford it then an Inverter is defiantly the way forward, however buzzbox or S/H oil cooled, (IF you've big arms) would be the cheapest route.....
A S/H oil cooled will outlast any Inverter but, as Snowcat says, it's hernia tackle lugging the things about! (if you need to do). DC Inverter will give the very best performance but you are into £300+ for something decent...around £100 for Chinese copy. For around £150ish you will get a decent AC transformer machine...look for one's with detachable leads, not wired in, which usually indicates the better quality models
weldequip