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A lap joint joins two pieces of metal by overlapping one edge over the other, then welding along the edge of the top piece. It is one of the easier joints to make with a stick welder, but the overlap creates a trap: the upper plate can hide poor fusion underneath. Good fit-up, clean steel, and controlled heat matter more than simply laying down a large bead.

Choose the Material and Electrode

For ordinary mild steel, a 3/32-inch E6013 rod is a forgiving choice for sheet and light plate. It runs easily, produces a smooth bead, and is available for either AC or DC machines. An E6011 rod is better when the steel is rusty or painted, or when you need stronger digging action, but it has a rougher arc and more spatter. E7018 produces a stronger, cleaner weld, though it requires cleaner steel and correct storage; low-hydrogen rods should be kept dry.

Check the amperage range printed on the electrode package. As a starting point, use about 70–90 amps for a 3/32-inch E6013, 75–95 amps for E6011, and 85–105 amps for E7018. The correct setting depends on plate thickness, welding position, machine polarity, and your travel speed. If you are buying a first machine, an inverter stick welder is generally easier to carry and holds a steadier arc than a large transformer machine.

Prepare the Lap Joint

Use steel of similar thickness when possible. A practical overlap is 1 to 1 1/2 inches. Less overlap gives you little room for a sound weld; much more adds weight without automatically adding strength. Remove mill scale, rust, paint, oil, and galvanizing from at least 1 inch on both sides of the weld line. A flap disc or wire wheel works, but do not rely on a wire brush to remove heavy mill scale.

Lay the smaller or thinner piece on top unless the design calls for another arrangement. Keep the plates flat and clamp them tightly. Gaps can cause burn-through on thin material and make the arc wander under the edge. Tack weld both ends and, on a long joint, add tacks every 3–4 inches. Alternate sides or allow the work to cool to reduce distortion.

Do not weld galvanized steel without proper controls. Zinc fumes can cause metal-fume fever. Remove the coating well away from the joint, provide strong ventilation, and use appropriate respiratory protection. Never weld painted, oily, or unknown containers until they have been safely cleaned and verified.

Set Up the Stick Welder

Connect the work clamp to clean metal, not to a rusty table or a loose clamp point. Set polarity according to the rod package. Many E6013 rods run on AC or DC, while E6011 commonly runs on AC or DC electrode positive. E7018 is often used on DC electrode positive, but the package instructions take priority.

Set the amperage near the lower end of the recommended range and make a short test bead on scrap of the same thickness. The arc should sound like a steady frying or soft crackling sound. Increase amperage if the rod sticks repeatedly, the bead sits high, or there is little fusion. Decrease it if the puddle becomes difficult to control, the edges melt away, or you burn through.

Wear a properly rated auto-darkening welding helmet, leather gloves, cotton or leather clothing, and substantial leather boots. Use welding screens around other people, remove flammable materials, and keep a fire extinguisher nearby. Stick welding produces ultraviolet radiation, hot slag, and sparks well beyond the immediate puddle.

Weld the Lap Joint

Strike the arc with a light scratch or tap, then hold a short arc—roughly equal to the electrode diameter. For a 3/32-inch rod, that means about 1/8 inch or less. Start at one tack and pause briefly until the puddle wets both the top plate edge and the lower plate. The goal is fusion into both pieces, not a bead sitting on top of the upper plate.

Use a slight work angle of about 45 degrees between the two plates, aimed into the corner. Keep the electrode tilted 10–15 degrees in the direction of travel. Travel steadily along the edge, watching the molten puddle rather than the bright arc. A small weave can help bridge a minor gap, but stringer beads are usually better for thin lap joints. Keep the bead width around two to three electrode diameters.

For sheet thinner than roughly 1/8 inch, use short welds of 1–2 inches, then move to another section. This limits heat buildup and warping. If the top plate starts to sag or the puddle suddenly drops through, stop immediately, let the work cool, and reduce amperage or increase travel speed. Do not try to fix burn-through by piling a large bead over a hole; patch the opening with clean metal or restart the joint properly.

Inspect and Clean the Weld

Let the weld cool enough to handle, then chip off all slag with a chipping hammer and brush it clean. Inspect for visible cracks, pinholes, undercut along either edge, trapped slag, and areas where the bead failed to touch the lower plate. Undercut appears as a groove melted into the base metal beside the bead. It usually indicates excessive amperage, excessive travel speed, or an overly long arc.

A cold lap looks like a rolled-over bead with a sharp line at its edge. It may appear neat but has poor fusion. Grind it out and reweld rather than trusting it. If the joint will carry a person, vehicle load, pressure, or lifting force, use an appropriate welding procedure and inspection method instead of relying on appearance alone.

When a Stick Welder Is Not the Best Choice

Stick welding is inexpensive and portable, and the equipment handles outdoor drafts better than MIG shielding gas. It is a good choice for gates, brackets, repairs, and heavier mild-steel work. However, thin sheet is easier with a MIG welder because wire starts and stops quickly with less slag. For a flux-core wire-feed welder, the cheaper option can be fine for occasional outdoor repairs, but it still produces slag and more spatter than gas-shielded MIG.

Choose TIG when the joint must be exceptionally clean or when welding stainless steel and aluminum with precise heat control. For a basic mild-steel lap joint, though, TIG is slower and costs more. A stick welder, a few suitable electrodes, solid clamps, and careful preparation are enough to produce a durable joint without buying equipment beyond the job.