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SPECIAL WELDING METHODS
Page 25
SPECIAL WELDING METHODS
SPOT WELDING
BURN THROUGH
PUNCH AND FILL
LAP SPOT
The purpose of a spot weld is to join pieces
of
metal together
with a "spot" of weld
instead
of a
continuous
weld bead.
There
are three
methods
of spot welding:
Bum-Through,
Punch and Fill, and
Lap.
Each
has advantages
and disadvantages
depending
on the specific application
as well as
personal
preferance.
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 diame-
ters tend to work better
than smaller diameters
because
they have greater
current carrying ca-
pacities
allowing
the arc to burn through very
quickly
while leaving a minimal amount
of filler
metal build up..030"
diameter solid wire or .035"
self-shielding flux-core
wire tend to work the best.
.024" diameter
solid and .030" self-shielding flux-
core
wires
should
not be used
with the
bum-
through
method
unless the metal is VERY thin or
excessive
filler metal build-up
and minimal
pene-
tration 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
produces
a
weld with the most "finished"
appearance
of the
three spot weld methods,
tn this method, a hole
is punched or drilled into the top piece of metal
and the arc is directed through this hole to pene-
trate into the bottom
piece.
The puddle
is al-
lowed to fill up the hole leaving
a spot weld that
is smooth
and flush with the surface
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 rec-
ommended above for the method of spot weld-
ing 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 perpendicular
to and about 1/4" off the work piece,
4. Pull the trigger on the gun and release it when it
appears
that the desired penetration
has been
achieved.
5. Make practice spot welds on scrap metal, vary-
ing 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.
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