I despise 1.6 rods with a passion. 2mm aren't much better in my experience but in fairness I haven't used enough of them to get a proper judgement. 2.5 are the best place to start imo, you can get away with a lot, but picking up bad habits isn't easy, with 3.2mm rods you can just drag the end of the rod on the metal and it will weld, try that with a 2.5 and you will find problems.
the 1.6mm rods burn away faster than a sneeze and are hard to control, or atleast that is what ive found with them.
Just spark up on some scrap with the rods you have and adjust the amps to suit you. The amp range is just a guide in my view, and like BB, I don't really faff around with rod sizes, I use 2.5s and 3.2s and adjust amps for each depending on the materiel I am working with.
I don't bother with rods below 2.5-I'd just MIG the job-but of course thats if you have the luxury of different processes to hand.
I agree - 1.6mm are quite difficult to use. You'll just waste them and get frustrated if you try to learn with them. Far too much flux in relation to metal in the rod, so you have a huge amount of slag and a small weld pool which makes it hard to maintain the arc length properly. 2.5mm are probably the best to learn on as there's a nice ratio of flux to metal in the rod, they burn down at a rate that's not too fast, and don't generate huge amounts of heat like 3.2 or 4.0mm rods do, meaning you don't need thick chunks of steel to practice on. 2.0mm are better than 1.6mm, but still more tricky than 2.5mm or 3.2mm - and in most cases you can get away with using 2.5mm rods and just being careful rather than risking a poor weld using 2.0mm.
Having said that, I have managed to use Aldi 1.6mm rods on my buzzbox to perform quite satisfactory welds on things like garden spades and lawnmower decks. But it takes a lot of practice to move the rod downwards fast enough to feed the weld pool and keep the arc length around 1mm, whilst moving sideways smoothly and fast enough not to blow holes. As with any form of welding, the more you practise the easier it gets.
Low as you can manage, test it what it reads and what it does can be two different things . Good luck, i should rather "blob in" downslope with a 2.5 if pushed on thinner stuff without the right tool for the job
I brought a job lot off eBay 1.6 s , 2s and 2.5s. its beyond me why they despatched them separately!
I did a bit tonight on some laminate plates and found the results ok, don't know if it was because the plates were thin? my technique needs a lot of work, but for a first attempt I'm getting on ok with the 1.6s so far, they do burn down like grease lightening :-)