2018 October 14    Metal & Shop

Introduction


The old-fashioned AC "buzz box" is widely considered to be a beginner-only machine.  Some people say you should just get a DC welder as fast as you can.

Is that really true? 

I don't know if we'll answer that conclusively, but let's take a look at this here AC welder.  And, of course, stick some metal together with it.


Welding & metalworking can be dangerous.  Use caution.  (Disclaimer.) 





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In This Article

Reliable Machine

Best Rods for AC Welding

Couple of Tips

Welding Thick Steel

Choosing an AC Stick Welder

Conclusion


Reliable Machine


Inverter welders are sort of complicated.  Bad caps, semiconductors got zapped or something... not that it happens all the time, but they can definitely go bad.

When something breaks and you have to finish the welding "right now", you can be more certain that an AC welder is going to work.  That's why it makes a good backup, even if you have an inverter welder.

That's one of the best things about an AC welder.  Simplicity and reliability.


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Best Rods For AC Welding


You might already know that 6013 is supposed to be a very easy electrode to work with.  Problem is, if you make the mistake of welding back over the slag or something, it produces awful welds.  (You're not supposed to weld back over slag, generally, but with 6013 it's a disaster.)  In fact, 6013 welds seem to get slag stuck in them a lot easier than with some of the other electrodes. 

7014 can work well on rusty metal or poor-fitup situations.  7014 might be a better choice for beginners.  Weld strength is not fantastic, though:  about the same as 6013, maybe a little better.

If you're welding something critical with AC, there are two electrodes that are favored.  6011 for rusty metal or poor fitup.  7018 AC for pretty much everything else.  7018 AC can produce the strongest welds of the bunch.

At first, 7018 AC was the only electrode that I could make decent-looking welds with.  Now I use it for almost everything where there's not rust, paint, or poor fitup.  I even weld cast iron with it, and though cast-iron welds have a good chance of cracking, 7018 AC has a better likelihood of working here than 6011, etc.  7018 AC restarts easier than regular 7018.  I usually heat these up before welding, to drive out the moisture.


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Couple of Tips


The Lincoln AC 225 has fixed amperage settings.  Let's say you're welding something where the ideal current would be 100 amps.  With the AC 225 you'll have to run at 105 amps, because there is no 100-amp setting.  So, the welds could be a little too hot, but they're probably close enough.

AC welders run a little more choppy than DC and tend to produce a bit more spatter.  But if you just need metal to stick together, it's not really an issue. 

Here's one that I've found very useful.  A lot of the perceived difficulty in welding with AC is just that... perceived.  Ignore the loud 60 Hz bog-down sound and the crackling arc noise.  As long as you can strike an arc and keep it going, you can actually make some welds that are very strong and look pretty good.  There is only one, real, physical difference I've ever noticed with an AC welder.  That is, the arc "wanders" maybe 5% of its width (at most) as you move it along.  So, your welds might look ever-so-slightly not-as-perfect.  I don't even know if that's significant, though, because the more I practice with AC welding, the more I cannot distinguish the difference between AC and DC welds.


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Welding Thick Steel


So I welded some 3/8" steel plate to some 1/4"-wall square tubing. 

Continuous, long 7018 welds are actually overkill for a job like this.  In fact it bent the 3/8" plate a little, because when the welds cool there's some contraction.  But overall, it looks like the current was pretty OK. 

These were with 1/8" Hobart 7018AC.  The first side was 135 amps, which was too hot even for 3/8" steel.  Weld spatter was high at 135 amps, and it was undercutting a lot.  So, for the other side (shown here) I turned the current down to 120 amps and it was just about right.




There were portions of this weld that were less-than-perfect, but overall it looks fairly decent.  It ought to hold. 

These kinds of projects are why I really like AC stick welding, though.  For the price, there's not much else that can easily weld 3/8" or 1/2" steel plate. 


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Choosing an AC Stick Welder


The AC welders that run on 120 volts will top out around 70 or 75 amps of welding current.  That's not really enough to run much, except maybe 3/32" 6011.  (Or, these.)

If you need a welder that runs on 120 volts, the inverter-based DC units can output a little more current.  In that case I would go for this welder, which tops out at 85-90 amps.  That allows use of 3/32" 7018 AC and 1/8" 6011.

For stick welding with AC, the 240 volt units are the way to go.  Figure on getting a 50-amp, 240-volt circuit installed if you want to run a Lincoln buzz box. 

The good ol' Lincoln AC225 is still a great machine.  There's a reason why the basic design hasn't changed in well over fifty years.  It works!  If you want DC capability too, they also make a combination AC / DC unit, which is their model # K1297.  (It will go up to 125 amps on DC, which means it can run 1/8" 7018.)


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Conclusion


There's a reason why old-style AC welders have been popular for generations.

I've heard tales of newer ones only lasting a few years, but there's not that much to go wrong with them.  The main thing is to make sure you're running them on a 50-amp circuit that's wired properly.  And also, watch the 20% duty cycle;  just don't sit there burning rod after rod without letting the machine cool down. 

If you compare an AC stick welding unit against one of those 120-volt wire-feed welders, the wire-feed can make nicer-looking welds (maybe).  But the AC stick welder has a much better chance of making a safe, strong weld.  And it can weld much thicker steel. 

I learned how to arc-weld on a Lincoln AC 225, and although my initial welds looked awful, pretty much everything I've welded (except for some cast iron) has remained stuck together.  Get an AC/DC welder if your budget allows it, but if not, there's nothing wrong with an AC-only stick welder.



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