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8.5 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 personal

preference.

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. 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.

2. 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 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.

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.