e. Spot Welding
There are three methods of spot welding: Burn-Through, Punch and Fill, and Lap. Each
has advantages and disadvantages, depending on the specific application as well as
i. 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. Wire
diameters that tend to work best, with the burn-through method are 0.035-inch,
self-shielding, flux-core wire. Do not use 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. Always select the HIGH
heat setting with the burn-through method and tune in the wire speed prior to
making a spot weld.
ii. 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 the hole to
penetrate the bottom piece. The puddle can 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.
iii. 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.
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