Fill Weld Techniques

Spiral

• If you're filling a round hole or an odd-shaped hole in thick material, start at the bottom edge and make a spiral. Build your weld-puddle all the way around the perimeter of the hole, then begin the lap adjacent to the bead you've just welded. Once you've filled one layer of the hole, repeat the process from the outer wall to the center, on top of the spiral you've just completed, until the hole is full.

Flat Stock Spirals

• Though there's less welding involved, filling a hole in flat stock or sheet metal is harder than filling a hole drilled into thick stock. When filling a hole in solid stock, you have a base to build on. With flat, thin stock or even thinner sheet metal, you have additional challenges. Using a spiral technique concentrates a lot of heat in a localized area, which causes material to warp. It's also easier to blow through thin material. Turn the amps down. When you're making your spiral, gravity will want to pull the semi-molten metal down through the hole. Spiral the pool in a low pyramid. This way, if the metal sags a little, it will sag into place.

Lacing Bridges

• Another approach is to start at one edge of the hole and make a small straight bead connecting one point on the radius to a second, adjacent point. This will fill in a flat spot across the hole, making it "D" shaped. Follow it with a lacing pattern, back and forth until the hole is filled.

Spots

• Spot welding techniques can augment each of the previous techniques. Typically, welds are continuous, leaving the bead to cool. With fills, the heat is concentrated, exaggerating this challenge. Rather than running a continuous bead, you can run short beads, then stop to let the metal cool. You can also weld one spot weld at a time.