Learn MIG Welding
1. Ground to clean, shiny metal, firmly.
This is critical for MIG welding with 120 volts.
Make sure your ground clamp has plenty of spring tension.
We make our own ground clamp from a vise grip.
2. Wire speed equals amperage.
When you increase wire speed you increase penetration.
If you are blowing holes in the metal, turn down the wire
speed. Reduce the amperage.
When MIG wire is poking the metal, turn down the wire speed.
3. Starting Settings, 120 volt MIG welding, inert gas:
(Most 120 volt MIG welders have number designations
like; 140, 135, 130, 120. Like the Lincoln 140, the
Miller 135, or the Hobart Handler 120).
Start around 50 inches per minute of wire speed.
(It is customary for these 120 volt MIG welders to
have a wire speed range of 0 to 100).
4. Set knob to 50. If the MIG wire looks like it is forming
drops of molten metal as you weld, turn the knob up to 55.
Increase it again if it still looks like drops.
Your MIG welding set up will be just right when you can see
liquid bits of molten metal shooting from the MIG wire into
the metal in a cone shaped spray. This is the "arc stream."
Settings above 65 or 70 will not add much. These 120 volt
MIG welders are played out above that.
5. Sheet metal MIG welding settings do require reduced voltage
I recently taught sheet metal MIG welding with a 140.
20 gauge did well at 2.5 volts and 25 inches wire speed.
14 gauge did well at 5.5 volts and 55 inches of wire speed.
6. Gas settings for MIG welders:
10 psi will be enough if you are indoors with no breeze or
moving air from fans, vents, or blowers.
If you are welding in a 20 mile per hour wind, set the gas
flow rate at 30 psi. Keep your gas flow rate 10 psi above
any air movement at the weld site.
If all other settings are correct and you are not getting nice
beads in wind conditions, turn the gas flow rate up another
20 psi. If that solves the problem go with it. If not, return
to the lower gas setting and find the actual problem. Too
much wind may require a swith to flux core process for
MIG welding machine applications.
7. Voltage Settings for 120 volt MIG welders:
Voltage settings are not as critical as amperage (wire speed)
settings. Normally you will be fine with a setting of 3 or 4
(choices 1 up to 4), C or D (choices A up to D). When you
are MIG welding thin metals, reduce the voltage (A or B).
8. Good metal fit up & preparation is a must.
120 volt MIG welding machines have limits. You will have
to be an experienced welder to fill gaps or holes with a 120
volt MIG welder. If there is a gap between metal edges you
plan to MIG weld, re-cut or grind them to fit together
closely. For non-professional welders, a gap greater than
the width of the MIG wire can be too wide. A gap the
width of the MIG wire or less will help with penetration on
thick metals. Remove gaps in sheet metal fit-up.
Make sure all metals are clean and shiny. You want to be
looking at "shiny white metal."
Remove mill scale. When you buy new steel it has a mill
scale build up on the surface. Mill scale looks grey. Hit it
with a grinder or wire wheel and you will see the white shiny
steel. Mill scale is not a conductor. Get it gone.
Remove all rust, oxidation, stains, coatings, and paints from
the weld surfaces. If there are pits, get the rust or oxidation
out of those also. Navy jelly helps.
Remove all grease, oils, road tar, and solvents. Remove
everything flammable. These cause porosity (tiny bubbles)
in the welds. Porosity means weak welds.
If you can not get it clean enough, switch to "Flux Core"
weld process with your MIG welding machine. It's
welding without gas with a MIG welder.
See my Flux Core page.
Make sure you have a steel surface to weld on and
plenty of weld clamps.
Metal moves when you heat it, so clamp it down. Once it is
clamped, weld from one end to the other. If you weld it
together at the ends, it will buckle or warp as you weld
between the ends. Then you get to cut it apart and start
all over again.
My students learn MIG welding in 2 or 3 hours.
Ask the Welder - anytime - anything.