Thread: Amps to metal thickness?

Most electrode packages have a current range and polarity information. Typically a general purpose electrode in a 2.5mm size will range from around 50/60 up to 90/100 Amps. The most common electrode that is used in a home situation is a 2.5mm, so a 130 Amp machine should be able to run that. With those size electrodes I've welded 1.2mm steel tube and the other day was welding some 6mm plate onto 8mm angle. Electrode size dictates the current requirements for stick welding, so a larger machine will allow a greater choice of electrode.
Joint preparation is for penetration. A stick welder will not penetrate metal more than 3mm (roughly) - electric arc welding is an edge joining process therefore to get better joints (more metal bonded) the joint is prepared. Generally it is not necessary for metal under 3mm as the weld produced should penetrate the joint adequately.
The big difference between a 130A machine and a 170A machine (I haven't looked at the actual specifications) is likely to be duty cycle (the proportion of time that it can weld without excessive heat build up). Once you start getting into industrial machines the larger machines usually have more features and are easier to use as they have some omph in reserve.

Hope this helps
Michael

Have you tried Miller - Welding Calculators

Originally Posted by Danger Mouse

Guys

I have tried various searches but am getting quite confused on the subject of what amperage in stick welders corresponds to what thickness of mild steel they are suitable for?

I understand preparation in joins such as veeing etc changes what thickness you can weld. But I am after a generalisation fo thickness range for a 130amp stick compared to a 170amp model.

If I generally weld 2-4mm mild steel is the 130 adequate?

Will the 170 do everything the 130 will do (down low) and then more at the top end?

I am looking at the smootharc 130 versus 170. 130 is cheaper (under $300) , lighter and has 10amp plug.

What I have found seems to be a correlation to amps and stick size. But I am not sure how to translate stick size to metal thickness?

I bought a smootharc 130 a while ago, and I'm not at all disappointed with it. It will use 3.2mm rods without a problem.

Originally Posted by Poit

I bought a smootharc 130 a while ago, and I'm not at all disappointed with it. It will use 3.2mm rods without a problem.

Same here - I usually run 3.2mm rods with mine, 2.5 and thinner only once in a blue moon, and at that point I'm probably eyeing off the MIG.

I wonder some times what the benefit of more amps would give - I guess the ability to run 4mm rods, and, as mentioned, better duty cycle.

Thanks heaps guys. Lots of really helpful info and comments.

No I hadn't seen the Miller calculator and admit I have no real idea about the different kind of rods available and what properties they exhibit. The store will have to give me some initial help for the right rods for mild steel 2-4mm.

It seems to me the BOC 130 will be a great unit to learn with and make a few things. If I decide I need more power or move to add a mig then the initial outlay I have made will not stop me from making a more informed purchase down the track. Spending under $300 for what is touted as a good unit sounds like a reasonable move. I'll get an auto darkening helmet and PPE gear and start practicing.

Thanks again

The 130 will run a 4mm rod well so no need to worry about upgrading later on.

Some more info for Danger Mouse. Another consideration for what amps are needed for whatever. Where I live this changes due to variations with the Electricity Distributors supply voltage, from time of day, to what day of the week it is. If you want the best possible welds do a practice run on the same sized scrap as you will be using and adjust the welder accordingly.
Hope this helps,
Regards,
Crocy.

I reckon that you will be more than happy with the 130A welder.
A 130A DC welder will punch out of all proportion to it's size. I have actually run 4.0mm E4818 electrodes at 95A on DCEP and they ran smoothly and fused well, (this is a lot lower than I would normally, but it was a special application). I would go so far as to say that you could actually drop up to 40% the amperage recommendations given on the packet when running DC and still get good performance.
Go for it and you won't look back!

This thread reminded me of some actual amperage tests I did a while back and posted here:
https://www.woodworkforums.com/f160/r...-tests-135398/

The BOC 130 showed it's capable of of delivering up to 160 amps, so I can imagine it'd drive a 4mm rod no problems.

The duty cycle on the 130 is not too bad either.