A stringer bead is a straight, narrow weld bead made by moving the electrode or torch along the joint without side-to-side motion. It’s one of the two fundamental bead types in welding, the other being a weave bead, which uses a zigzag or oscillating pattern. Stringer beads produce a narrower deposit, lower heat input, and a more controlled weld pool, making them the go-to technique for many joints, positions, and code-governed applications.
How a Stringer Bead Differs From a Weave Bead
The core difference comes down to torch movement. With a stringer bead, you travel in a straight line (or very nearly straight) along the joint. With a weave bead, you swing the electrode side to side as you travel, covering a wider area per pass. This difference in movement directly affects travel speed: stringers move faster, weave beads move slower.
Because travel speed sits in the denominator of the heat input equation, stringer beads deliver less heat into the base metal per unit length. That matters for the material’s mechanical properties. High heat input tends to reduce toughness, especially in the heat-affected zone (the strip of base metal right next to the weld that gets hot enough to change its grain structure). For high-strength or quenched-and-tempered steels, excessive heat can significantly degrade the properties that make those steels useful in the first place. This is why fabricators working with these materials often default to stringer beads or strictly limit how wide a weave bead can be.
For mild steel where toughness isn’t a primary concern, both techniques can meet minimum tensile and yield strength requirements. But when a welding procedure specification (WPS) has been qualified through testing, the allowable heat input range often pushes fabricators toward stringers simply because they’re easier to keep within that envelope.
Technique: Angles, Arc Length, and Travel
Running a clean stringer bead is less about special skill and more about holding a few variables steady at the same time. The three main ones are work angle, travel angle, and arc length.
Work angle is how you position the electrode relative to the joint when you look at it from the end. For a butt joint, hold the electrode at 90 degrees, perpendicular to the surface. For T-joints and fillet welds, split the difference between the two plates, which puts you at roughly 45 degrees.
Travel angle is the tilt of the electrode along the direction you’re moving. In most positions, a drag angle of 5 to 15 degrees works best. That means tilting the electrode back slightly, away from the direction of travel. This keeps the slag behind the arc where it can protect the cooling weld metal rather than running ahead into the puddle and causing inclusions. The one exception is vertical-up welding, where a slight push angle of 5 to 10 degrees helps support the molten pool against gravity.
Arc length should roughly equal the diameter of the electrode’s core wire. Keeping a tight, consistent arc reduces spatter and gives you better control over penetration. One practical tip from experienced welders: tune your machine on flat plate first. Set the heat so the rod just barely stays lit with a tight arc, then adjust upward from there until you get good fusion without losing control of the puddle.
Amperage Settings by Electrode Size
For one of the most common electrodes, 1/8-inch 7018 on DC electrode positive, most welders land between 120 and 130 amps for stringer beads in the flat and vertical-up positions. Some run as low as 90 amps or as high as 135, depending on material thickness and fit-up. The practical approach is to start at the middle of the electrode manufacturer’s recommended range and adjust: if the puddle is too fluid to control, drop the amps; if the rod keeps sticking or the bead looks cold and ropy, bring them up.
Smaller electrodes need proportionally less heat. A 3/32-inch 7018 rod on thin-wall tubing (around 3mm) might run at 65 to 75 amps. Going too hot on thin material risks blowing through entirely, which is difficult to repair, especially in the vertical position.
For vertical-up stringer beads, a common rule of thumb is to reduce amperage by about 10% compared to your flat-position setting and travel at roughly half the speed you’d use in flat. The slower pace and lower heat give you time to keep the puddle from sagging.
Building Up Thickness With Multiple Passes
Stringer beads really prove their value in multi-pass welding, where you fill a thick joint by stacking and overlapping narrow beads. Each pass fuses to the base metal and to the previous bead, building up the weld layer by layer. This approach gives you precise control over heat input on every pass, which is harder to achieve with wide weave beads.
The key variable in multi-pass work is how much each bead overlaps the one beside it. Research on bead overlap consistently shows that placing bead centers at about 60% to 73% of the bead’s base width produces a defect-free profile. In practical terms, if your stringer bead is 10mm wide, you’d offset the next bead’s center by 6 to 7mm. Too little overlap leaves valleys between beads that trap slag or create lack-of-fusion defects. Too much overlap wastes time and adds unnecessary heat.
Overlap around 60% of the bead width tends to minimize lack of fusion specifically, while values up to 73% are still acceptable as long as the bead geometry stays consistent along its length.
Common Defects and What Causes Them
The defects that show up in stringer bead welding are the same ones that plague all welding, but some are more likely depending on your technique errors.
- Lack of fusion is the most relevant risk with stringer beads, especially in multi-pass joints. It happens when the new weld metal doesn’t bond to the sidewall, the root, or a previous pass. The usual culprits are current set too low, arc aimed away from the joint edges, or an overly narrow root gap. In fact, welding codes sometimes recommend stringer beads specifically to prevent lack of fusion on narrow roots, because the focused arc penetrates more directly than a wide weave.
- Undercut appears as a groove melted into the base metal along the edges of the bead that doesn’t get filled by weld metal. It’s typically caused by traveling too fast, running too hot, or holding an incorrect work angle that concentrates the arc on one side.
- Porosity shows up as gas pockets trapped in the solidified weld. With stringer beads, the most common cause is too long an arc length, which allows atmospheric contamination, or moisture on the electrode or base metal.
- Slag inclusions occur when slag from a previous pass isn’t cleaned off before the next bead is laid. In multi-pass stringer work, thorough chipping and wire brushing between passes is non-negotiable.
When Stringer Beads Are the Better Choice
Stringer beads aren’t always required, but several situations make them the clear preference. Overhead welding is one: the small, fast-freezing puddle of a stringer bead is far easier to control than a wide weave when gravity is pulling molten metal toward you. Vertical-up welding on thinner material is another, where keeping heat input low prevents burn-through and distortion.
Any application involving quenched-and-tempered or high-strength low-alloy steels tends to favor stringers because these materials lose their engineered properties when overheated. Bridge fabrication under AWS D1.5, for instance, often involves discussions about stringers versus weaves precisely because of the toughness requirements in the heat-affected zone.
Interestingly, major welding codes like AWS D1.1 (structural steel) don’t explicitly limit bead width for stringer beads. The code controls heat input and interpass temperature instead, leaving bead width as an indirect consequence of staying within those limits. A common shop guideline is to keep stringer beads no wider than one to two times the electrode diameter, but that’s a practical convention rather than a code mandate.
For beginners, stringer beads are also the foundation of learning arc control. The technique strips away the complexity of oscillation patterns and forces you to focus on the fundamentals: steady travel speed, consistent arc length, and correct angles. Once those become second nature, weave patterns are much easier to pick up.