Forney MIG 180FI, Operating Manual

Page: 23 / 38

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Punch and Fill, and Lap (see Figure 20).
Each has advantages and disadvantages
depending on the specific application as well
as personal preference.
Figure 20. Spot Welding
1. The BURN-THROUGH METHOD welds
two overlapped pieces of metal together
by burning through the top piece and into
the bottom piece.
With the burn-through method, larger wire
diameters tend to work better than smaller
diameters because they have greater cur-
rent carrying capabilities allowing the arc
to burn through very quickly while leaving
a minimal amount of filler metal build up.
Wire diameters that tend to work best,
with the burn-through method, are 0.030
inch diameter solid wire or 0.035 inch self-
shielding flux-core wire.
Do not use 0.024 inch diameter solid or
0.030 inch self-shielding flux-core wires
when using the burn-through method
unless the metal is VERY thin or exces-
sive filler metal build-up and minimal pen-
etration is acceptable.
Always select the HIGH heat setting with
the burn-through method and tune in the
wire speed prior to making a spot weld.
2. The PUNCH AND FILL METHOD pro-
duces a weld with the most finished
appearance of the three spot weld meth-
ods. In this method, a hole is punched or
drilled into the top piece of metal and the
arc is directed through the hole to pene-
trate into the bottom piece. The puddle is
allowed to fill up the hole leaving a spot
weld that is smooth and flush with the sur-
face of the top piece.
Select the wire diameter, heat setting, and
tune in the wire speed as if you were
welding the same thickness material with
a continuous bead.
3. The LAP SPOT METHOD directs the
welding arc to penetrate the bottom and
top pieces, at the same time, right along
each side of the lap joint seam.
Select the wire diameter, heat setting, and
tune in the wire speed as if you were
welding the same thickness material with
a continuous bead.
SPOT WELDING INSTRUCTIONS
1. Select the wire diameter and heat setting
recommended above for the method of
spot welding you intend to use.
2. Tune in the wire speed as if you were
going to make a continuous weld.
3. Hold the nozzle piece completely perpen-
dicular to and about 1/4 inch off the work
piece.
4. Pull the trigger on the gun and release it
when it appears that the desired penetra-
tion has been achieved.
5. Make practice spot welds on scrap metal,
varying the length of time you hold the
trigger, until a desired spot weld is made.
6. Make spot welds on the actual work piece
at desired locations.