The Bead: Angle, Arc & Travel
A sound stringer bead is four variables held at once — work angle, travel angle, arc length, travel speed — and its width and ripples report exactly how well you held them. · 12 min
The arc is lit. Now you keep four things true at the same time, for the length of the plate. Hold the rod near 90 degrees to the surface, seen from the front. Lean it 5 to 15 degrees in the direction of travel, dragging. Keep the gap at one rod diameter. Move at one steady speed. Each variable has its own job, and the finished bead — a stringer bead, one straight pass run without weaving — records how you did on all four.
Guess before you learn
You run a stringer with a 1/8-inch rod at the right speed. About how wide should the finished bead be, in inches?
About a quarter inch — twice the rod's diameter. Wider and flatter usually means you lingered; narrower and taller means you outran the puddle. Keep your guess in pencil: the second half of this folio is entirely about reading widths.
9–12
3–5
Four controls, one hand. Straight up and down, seen from the front, so the heat spreads evenly to both sides. A small lean the way you travel, so the arc pushes the melted crust behind you. The small gap. And a steady pace, because the puddle needs the same amount of time everywhere.
If any one control drifts, the bead shows it: too much lean makes a messy line, rushing makes it skinny, and lingering piles it up tall and wide.
6–8
Name them properly. Work angle: rod to plate, viewed along the joint — hold near 90° so both edges of the bead wet in evenly. Travel angle: the lean in the direction of motion — a 5–15° drag for stick, meaning the rod tips back toward the finished bead. Arc length: one rod diameter, from folio 7. Travel speed: whatever pace keeps the arc on the leading edge of the puddle.
The drag matters because the arc has force. Dragging directs that force — and the molten slag the coating sheds — back over the finished bead instead of ahead of it, where slag would be welded over and trapped inside the joint.
9–12
Heat delivered per inch is the ruling quantity. Raise the travel speed and each inch of joint receives less energy and less filler, so the bead narrows and humps up. Slow down and each inch soaks longer and takes more metal, so the puddle spreads wide and piles high. Width tracks time-at-temperature almost directly — it is the most honest measure of your pace.
The ripples record solidification: each shingled crescent is where the trailing edge froze while the arc moved on. Even spacing means even speed. Ripples stretched into points mean hurry; ripples crowded into stacked crescents mean crawl.
K–2
Hold the stick straight up when you look at it from the front. Tip it a little toward where you are going. Keep the tiny gap. Move along at one even speed.
Do all four at once, and the melted line comes out the same width the whole way.
Undergrad
Quantitatively, heat input HI = 60 × V × I / (1000 × S), in kJ per inch with S in inches per minute. At 22 V, 125 A, and 6 in/min: about 27.5 kJ/in. Bead cross-section scales with deposition per unit length — the rod melts at a nearly fixed rate, so slower travel lays more metal per inch — while penetration peaks at moderate speed: too slow, and the thick puddle cushions the arc away from the base metal.
Work angle redistributes arc pressure and wetting: tilted off 90°, one toe of the bead runs hot while the cold toe invites lack of fusion. Travel angle trades penetration for coverage — a near-vertical drag digs deeper; a long lean flattens and widens the bead but risks rolling slag ahead of the arc.
Postgrad
The puddle is a coupled system: arc pressure depresses the free surface, surface-tension gradients circulate the melt, and the solidification front trails the heat source at exactly the speed you set. Ripple spacing scales with travel speed against the freezing rate of the trailing edge — pace literally becomes texture.
Defect thresholds bound the parameter window. Excess arc length raises voltage and broadens the arc root, melting the toes without refilling them — undercut. Excess speed starves the toes of wetting time — a convex, ropey profile with cold-lap risk. Reading geometry against these mechanisms turns inspection into diagnosis, which is folio 11's entire subject.
stringer bead
A single straight pass run without side-to-side weaving. The first bead every welder learns to keep even.
Here is the payoff for all that holding: the bead is evidence. At the right speed, a stringer runs about twice the rod diameter wide, with even, shingled ripples — each new crescent lapping the one before it. Run too fast and the puddle never spreads: the bead comes out narrow, tall, and ropey, its ripples stretched to points. Too slow and the puddle sprawls: wide, high-crowned, heavy. You can read yesterday's travel speed in today's cold steel.
Two habits finish the skill. First, restarts: any bead longer than one rod ends in a crater — the shallow dish where the arc stopped. Chip and brush it, strike about half an inch ahead of it, swing the arc back into the crater until the new puddle wets the old bead, then travel on; done well, the tie-in disappears into the ripples. Second, slag: the crust protects the bead while it cools, so it stays put until the bead has frozen — then chip and wire-brush before you inspect or weld over it. Chipping hot throws glassy shards; be glad the safety glasses are already on.
Tie in a restart — the steps fade as you master them
Chip the slag and wire-brush the last inch of bead
Half an inch ahead of the crater, on the joint line
Swing the arc back into the crater and hold until the new puddle wets the old metal
Resume the normal drag angle and pace — the tie-in should vanish into the ripple pattern
Four variables, one steady hand, and a bead that reports on all of them. Run stringers until twice-the-diameter is what your hand produces unasked; every later process and joint builds directly on this one skill. Next unit, the wire feeder takes over two of the four variables for you — and by then you will know exactly which two.
Practice — new ink and old, interleaved
1.In one sentence: what does the moving tip create that a held touch never does?
2.One sentence: a finished bead is evidence — of what, exactly?
3.A 1/8-inch E7018 (0.125 inch). Rule-of-thumb starting amperage?
4.Bead width target with a 3/32-inch rod, in inches?
5.From memory: the four variables of a stringer bead, with a number for each.
Work angle near 90°; travel angle a 5–15° drag; arc length one rod diameter; travel speed steady — the pace that keeps width at about twice the rod diameter.
How close were you? Grade yourself honestly — it sets your review date.
6.Both toes of your bead show melted grooves the weld never refilled. First two suspects?
7.Match each situation to its outcome.