The chart on the PrimeWeld MIG180 did seem to be dead nuts for a horizontal fillet weld.
Chart settings for short circuit mig wire speeds are usually too hot for vertical uphill but the chart is still a good starting point.
All you need to do for vertical uphill is use the chart and select some settings for 1 or 2 thicknesses lower than what you are welding vertical and that usually works out just fine....Especially if you lower the recommended short circuit mig wire speed by about 10%.
But not all mig welders have a chart and occasionally, you might be required to do some mig welding with someone else’s machine that not only does not have a chart, but does not have any markings on the voltage and wire speed knobs.
Or worse yet, there is no knob. Just a pair of vise grips clamped where the knob should be.
So it pays to have a working knowledge of how to set voltage and wire speed without a chart.
The first basic principle that is helpful is to know the approximate voltage range that works with short circuit mig.
No matter what size wire is used, the voltage range for short circuit mig welding is approximately 14-24 volts with C25 gas. (Co2 voltage is more like 16-25 but we are strictly dealing with c25 75/25 here)
Thin wire like .023” works best with the lower voltage and larger diameter wire works better for the higher end of the range.
.035” wire is very commonly used for the higher end of the voltage range and also works pretty well down to around 16 volts.
.030" wire is a really good all purpose wire if you occasionally weld really thin metal but often weld 1/8" thickness.
Keep in mind that mig machines are all a bit different... especially now that there are both inverter and older style transformer units in use that have different arcs.
For example, I had a Thermal arc mig welder that would not even melt .035" wire at 14 volts.
So if the voltage range for short circuit mig welding is 14-24 That’s a range of 10 volts….
Thats pretty convenient.
Because I know that 3/8" is the max thickness the companies like Miller electric list on their mig settings charts at 24 volts and 24 ga is the minimum with a recommended 14 volts.
24 gauge steel is .024” thick and is pretty close to the thinnest metal that can be efficiently welded using short circuit mig.
14 volts would be pretty close for that.
Miller electric weld calculator recommends 3/8” as the maximum thickness for short circuit mig.
So if 14 volts is the low end of the range for .024” thick steel
And 24 volts is the high end of the voltage range for 3/8” thick steel…
Then I can pretty quickly make a good guess at what voltage I might need for 3/16” thick steel because its roughly half way in between .024” and 3/8”.
Half way between 14 and 24 volts is 19 volts.
Now lets check that against miller electric weld calculator and mig charts
Boom! It just so happens that both millers mig calculator and mig welder settings charts call for 18-19 volts for 3/16” carbon steel using C25 gas.
Wire speed is just as important..maybe even more important since wire speed controls amperage.... but you need a certain voltage to make the arc efficient.
Now that we know what voltage is needed for a thickness
How do we set wire speed?
Again, mig settings charts are usually pretty good.
But if you don’t have a chart, here are a few tips for how to tell when wire speed is right.
In the video at the top of the page, you will see that a fairly wide range of wire speed settings worked pretty well.
If you have a good chart on your mig welder, I would recommend using the wire speed settings listed but trim back the wire speed by about 10%.
If your mig welder does not have a chart, then another way to set wire speed is to first set voltage according to the 14-24 volt range.
Then pick a wire speed setting that is in the middle of the range.
Get a piece of scrap metal and lower wire speed until it rattles and pops.
Thats too low.
Now increase wire speed until it stubs into the puddle and piles up.
Thats too high.
somewhere right near the middle of that range will give you a good smooth arc that sounds like bacon frying.
24 volts for 3/8" thick
19 volts for 3/16"
14 volts for 24 ga (.024")
Adjust for anything in between. for example for 1/8" thick, lower voltage a bit to 18 volts.
3/8” -24 volts
5/16” - 22 volts
1/4” - 20 volts
3/16” 19 volts
1/8” 18 volts
1/16” 17 volts
18 ga 16 volts
20 ga - 15 volts
22 ga - 15 volts
24 ga- 14 volts