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SPECIAL WELDING
METHODS
SPOT WELDING
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:
Burn-Through, Punch and Fill, and Lap
(see Figure 15). Each has advantages
and disadvantages depending on the
specific application as well as personal
preference.
PUNCH AND FILL LAP SPOT
BURN THROUGH
Figure 15. Spot Weld Methods
. 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 current
carrying capacities 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 excessive
filler metal build-up and minimal
penetration is acceptable.
24
2,
,
Always select the HIGH heat
setting with the burn-through
method and tune-in the wire speed
prior to making a spot weld.
The PUNCH AND FILL METHOD
produces a weld with the most
finished appearance of the three
spot weld methods. In this method,
a hole is punched or drilled into the
top piece of metal and the arc is
directed through this hole to
penetrate into the bottom piece.
The puddle is allowed 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.
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 head.
SPOT WELDING INSTRUCTIONS
1. Selectthe wirediameter and heat
settingrecommendedaboveforthe
methodofspotweldingyouintend
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 inch
off the work niece.
4.
Pull the trigger on the gun and
release itwhen it appears that the
desired penetration has been
achieved.
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