Weld Bead Definition: Types, Shapes, and Defects Explained

A first-year apprentice lays what he thinks is a perfect stack-of-dimes bead on a practice plate, hands it to the inspector, and gets it rejected for undercut he couldn’t even see without a flashlight. The bead looked great — but looking great and being sound are two different things, and that gap is exactly where the weld bead definition stops being trivia and starts saving careers.

What Is a Weld Bead? The Definition, Answered Early

A first-year apprentice hands a practice plate to the inspector, proud of a neat “stack of dimes” bead. The verdict: rejected for undercut so shallow he never thought to look for it. The bead looked textbook-perfect, but appearance and soundness are two different things. That gap is exactly why the weld bead definition is not trivia. Once you know what a bead actually is, per code, every drawing callout, WPS range, and inspector comment suddenly makes sense.

The Formal Definition, Straight From the Standard

In plain shop language, a weld bead is a deposit of weld metal laid down in one continuous movement of the arc. The formal wording comes from AWS A3.0M/A3.0, Standard Welding Terms and Definitions, which defines a weld bead as “a weld deposit produced by a single pass of a welding process.” Three words in that sentence do all the heavy lifting:

• Deposit means solidified filler plus, where applicable, melted base metal. It is the finished metal, not the arc itself.
• Single pass means one uninterrupted progression from the start of the bead to the stop. Stop, re-strike, and continue, and you now have two beads joined together.
• One welding process means SMAW, GMAW, FCAW, GTAW, SAW, and so on. A bead is never a mixture of processes.

The glossary also notes that a bead may be narrow or wide, depending on transverse oscillation. That single clause is the seed of the stringer-versus-weave distinction, and it is why bead width is a technique decision, not an accident.

Bead, Weld, Pass, Layer, and Bead Weld Are Not Synonyms

Inspectors, welders, and engineers use these words precisely, and mixing them up costs time on a job site. Here is how AWS separates them:

Term	What it means	Practical way to think about it
Bead	A weld deposit produced by a single pass of a welding process	One stripe of metal laid down in one motion
Pass	A single progression of welding along a joint, weld edge, or weld surface, from start to finish	The physical act of running that bead
Weld	The complete joint produced by the joining process, including all passes, beads, and layers	The finished assembly, judged as a whole
Layer	A series of beads placed side by side or stacked on top of one another within a weld	One horizontal “course” of a multi-pass groove weld
Bead weld	A weld composed of one or more string or weave beads deposited on an unbroken surface	Beads laid on a flat plate, not into a joint

So a single butt joint can hold a dozen beads arranged in several layers, yet remain one weld. And a surfacing run on an unbroken plate is a bead weld, not a groove weld. If this feels like word-splitting, remember that the AWS glossary defines more than 1,500 welding and allied-process terms, including a dedicated figure categorizing weld bead types, precisely so shop-floor language and code language match.

Why the Exact Definition Matters on Real Work

Three places punish loose terminology:

• Drawing callouts. A drawing that specifies a fillet size, a groove depth, or “bead weld, 2 passes” is describing beads and passes. Misread it and you weld the wrong geometry entirely.
• The WPS. A Welding Procedure Specification records the number of passes, whether stringer or weave beads are permitted, and required interpass cleaning. Weld outside those conditions and the procedure no longer qualifies the joint, no matter how good the bead looks.
• Inspector language. “Undercut at the toe of the cover bead” tells you exactly where to look and what to fix. Vague words like “line” or “seam” get you nowhere.

Bead Width vs. Oscillation: The One Variable Inside the Definition

Because the definition says a bead may be narrow or wide depending on transverse oscillation, width is something you control deliberately. Hold a steady line with no side-to-side movement and you deposit a stringer bead, typically only two to three electrode diameters wide. Move the electrode side to side as you travel and you deposit a weave bead, which can cover four to six times the electrode diameter. Same single pass, same single bead, very different heat distribution, bead profile, and finished strength. That comparison, along with when codes limit weaving, gets a full treatment in the next section.

Bottom line: a bead is one deposit from one pass. Everything else in welding, from joint fill sequences to acceptance criteria, is built on top of that single definition.

Anatomy of a Weld Bead: Face, Toe, Root, Ripples and Throat

Every weld bead tells a story. For an inspector, it’s a map of heat, speed, and technique. For a welder, it’s instant feedback. To read that story correctly, you must know each part of the bead and what it reveals about the weld underneath.

The Visible Surfaces: Face, Toes, and Reinforcement

The most obvious feature is the face, which is the outer, exposed surface of the weld bead. Directly where that face meets the base metal are the toes. The tie-in at the toes is one of the first places an inspector looks, as a poor merge here is a common starting point for cracking.

Rising above the base metal on many welds is the reinforcement. This extra weld metal adds strength in theory, however, excessive reinforcement creates unnecessary stress risers. Too little reinforcement, known as underfill, can do the exact opposite. For visual acceptance, AWS D1.1 requires weld reinforcement to be flush to 1/8 in (3 mm) above the plate, and undercut no deeper than 1/32 in (1 mm).

The Hidden Side: Root, Throat, and Leg Length

On the opposite side of the face lies the root, the deepest point of fusion between the weld metal and the base metal, or between passes. From a strength standpoint, the most important measurement is the effective throat. This is the shortest distance from the root of the joint to the face of the weld, not the full height of the reinforcement.

For fillet welds, welders also measure leg length, which is the distance from the root of the fillet to the toe. Two fillets can have the same leg length, yet entirely different effective throats depending on their profile. For groove welds, the geometry differs entirely, as fusion is driven into a prepared joint rather than being built in the corner of two plates.

Angles, Axis, and Bead Placement

Before a single drop of metal is deposited, orientation is already shaping the bead. The weld axis is an imaginary line through the center of the weld parallel to the bead; travel angle is measured from the weld axis. Specifically, the travel angle is the angle between the electrode axis and the weld axis, with push (forehand) and drag (backhand) being its two directions. The work angle is the angle between the electrode axis and the work surface, and adjusting both in tandem is what keeps a bead symmetrical.

These angles become even more crucial for precise processes, such as those covered in Aluminum MIG Welding: The Complete Practical Guide, where even a slight change in angle can heavily impact profile and puddle control.

Ripples, Slag, and the Heat-Affected Zone

The distinctive ripples seen across a bead are the frozen contour of the molten puddle. Consistent, tightly spaced ripples often indicate steady travel speed and proper heat control, whilst erratic, wide ripples can be a red flag. A short note on reading them: sudden changes in ripple spacing along a single bead are often more telling than their shape alone, as it can indicate unsteady hand movement.

With processes that produce a flux coating, such as SMAW, slag will form over the bead. Slag is not part of the weld; it must be fully removed between passes or it forms slag inclusions that weaken the bead. Never allow slag to be buried underneath the next layer, as it is one of the hardest discontinuities to detect from the face alone.

Finally, underneath every bead lies the heat-affected zone (HAZ). While not part of the deposited weld metal itself, this altered area of base metal has undergone microstructural changes from the weld’s heat. A welder may not see the HAZ, but an inspector knows that excessive heat input to create an oversized bead can widen it, increasing its susceptibility to hardness issues.

Stringer Bead vs Weave Bead: The Two Fundamental Bead Types

Every pass you lay comes down to one simple decision: do you drag the arc straight, or do you move it side to side? That motion is what splits weld beads into the two most fundamental categories. According to AWS A3.0, a stringer bead is made without appreciable transverse oscillation, whereas a weave bead is made with transverse oscillation. While it may seem like a matter of comfort, this distinction has a massive impact on heat, fusion, and overall weld quality.

Size and Width Ratios

The path of travel directly changes the width of the deposit. For shielded metal arc welding (SMAW), a general rule of thumb holds true for most applications:

• Stringer beads: Tend to be roughly 2-3x the diameter of the electrode being used.
• Weave beads: Tend to fall between 4-6x the electrode diameter, depending on the amount of oscillation used.

With that said, width can get out of hand very quickly. A widely taught textbook rule is that a weave width should not exceed about twice the electrode diameter. Going any wider than that is almost always excessive for fusion and heat control. For wider joint faces, it is far more reliable to stack multiple stringers than it is to try and “stretch” one massive weave across the groove.

Heat Input, HAZ, and Interpass Temperature

The biggest trade off between the two is thermal. A stringer bead keeps the arc focused in a narrow line, concentrating fusion directly below the puddle with minimal time spent dwelling on the cooler surrounding metal. This is exactly why stringer beads minimize heat input, interpass temperature, and the width of the heat-affected zone (HAZ).

Weaving is the opposite. By spreading the arc side to side, the puddle is held open for longer, depositing more metal over a larger area. This raises heat input, increases interpass temperature, and widens the HAZ. As stated by Iowa DOT IM 558, heat input is lowered by reducing current or increasing travel speed, making the stringer technique generally superior for heat control. With that being said, deposition rate for weaves can be higher on wide, open faces, however that speed of deposition almost always comes at the cost of excess heat.

Weave Patterns and Dwell Points

Not every weave is a haphazard wiggle. Controlled oscillation is the key to a sound weave bead. The three patterns seen most often in the shop are:

• Zig-zag: A consistent triangle-like motion from toe to toe. This is one of the easiest patterns to control and is commonly used on flat cover passes.
• Crescent weave: A rounded, U-shaped motion. This helps keep a more even puddle and is very useful when trying to avoid a peaked, humped bead.
• J-weave: A motion that goes up one side of the puddle and returns along a tighter path. This is often utilized for out-of-position work, as it gives more control over puddle manipulation.

The most overlooked detail to all of these patterns are the dwell points. Pausing momentarily at the edges of the puddle adds both heat and metal where the joint edges need it most, promoting proper tie-in and fusion into the toes. Rushing across the toes without a dwell is one of the quickest ways to create an un-fused edge, no matter how pretty the middle of the bead looks.

When To Use Each One

Knowing why to pick one over the other is what separates a procedure-following welder from a guessing one. For all-position welding, this decision becomes even more crucial:

• Use stringer beads for groove fills and multi-pass joints: Their low heat input keeps distortion down, allows for better interpass temperature control, and drastically lowers the chance of trapping excess heat between passes. They are the workhorse for thick groove welds for a reason.
• Use weave beads for cover passes, wide surfaces, or open roots: Weaves excel when you need to tie in across a larger width, flatten a convex profile, or help manipulate a puddle in vertical or overhead positions. However, this should be done in a tight, controlled weave, never an unrestricted side-to-side wash.

At the end of the day, the goal isn’t to pick the “flashier” motion. It’s to pick the motion that gives the required fusion with the least amount of unnecessary heat. For the vast majority of groove welds, the answer will be stringers. For carefully controlled cover passes, a tight weave can absolutely have its place. The art is knowing when to switch between the two, and when to resist weaving altogether.

Bead Types, Pass Sequences and How a Joint Gets Filled

Not every weld is a single run. For most code-quality joints, multiple beads must be stacked, cleaned, and tied together to safely fill a prepared groove. Knowing the order of these beads, when to run a stringer or weave, and when a joint doesn’t even require filling at all is a skill that separates a consistent welder from a guesser.

The Standard Pass Sequence For Groove Joints

While every joint varies based off of its bevel and thickness, the majority of multi-pass groove welds follow this general progression:

• Root pass: The first bead deposited into the prepared groove. Its sole priority is achieving the required penetration and fusion at the root. For this pass, stringer beads are almost always chosen to allow for precise control over heat input and the root profile.
• Hot pass: Immediately following the root, this bead is ran with slightly higher heat to burn out any minor slag pockets or trapped impurities left behind. Many times this is ran with a controlled stringer to reinforce the root without blowing it out.
• Fill passes: These are the workhorse beads used to build up the bulk of the groove. As a rule, a multiple-pass layer in manual groove welding is made with stringer beads. Stacking narrow stringers side by side allows the welder to control interpass temperature, minimize distortion, and limit the size of the heat-affected zone.
• Cap/cover pass: The final visible layer of the weld. Cover passes are commonly widened with a weave bead to stretch fully across the joint, especially on pipe. This wider weave allows for a smooth, uniform transition to the base metal without having to cram an excessive amount of stringers across the face.

Backing Welds and Back Beads

Not all access is from one side. For single-groove joints with critical penetration requirements, two terms are often mixed up, however they are not interchangeable.

A backing weld is deposited at the back of a single-groove weld to back the subsequent passes, providing a support for the root pass when welded from the opposite side. A back bead, on the other hand, is applied from the root side after back-gouging the original root. This is done to remove any suspect material from the first side and replace it with a freshly deposited, inspected sound bead. Both are utilized to ensure full, code acceptable penetration, however the timing and side of deposition is what sets them apart.

Non-Joint Beads: When No Groove Is Being Filled

Beads aren’t always used to join two pieces of metal together. Plenty of them are ran strictly onto an unbroken surface:

• Bead weld on unbroken surfaces: A single or series of beads deposited directly onto a solid plate with no joint gap to fill. These are often used for tests, builds ups, or pad welds.
• Surfacing/hardfacing beads: Ran to add a layer of wear, corrosion, or impact resistant material onto a base metal. These beads are layered with precision, often utilizing stringers to limit dilution between the build up alloy and the parent material.
• Tack welds: These are small, temporary beads used to hold parts in alignment prior to welding out the full joint. While small in size, they must be fused properly, as a badly cracked or cold tack can carry straight into your root pass if left unaddressed.

Single-Pass vs Multi-Pass and The WPS

The decision to run a single-pass or multi-pass weld is dictated by the joint design, thickness, process, and code. Thin material can often be fused in one pass, however thicker sections require multi-pass layering to achieve the required throat without sacrificing control of heat input.

Due to this, a Welding Procedure Specification (WPS) is far more detailed than just listing amperage and voltage. WPS technique records commonly include bead type (stringer/weave), number of passes, passes per side, travel angle and interpass cleaning method. Each of these are verifiable, and as stated within the requirements of AWS D1.1, deviating from them can be outside of the qualified procedure. Furthermore, the terminology that these records are written off of are defined within AWS A3.0 to keep shop and inspector language consistent.

Most importantly, interpass cleaning is never an afterthought. Between every fill and cover layer, any loose slag, spatter, or contaminants must be removed. Skipping this step is one of the fastest ways to trap inclusions, especially between stringer beads where valleys can be easy to miss. With the correct sequence, the correct bead type for each layer, and adherence to the WPS, all of these individual beads will fuse into one solid, continuous weld. For projects that require pristine surface prep prior to these multi-pass builds, utilizing a proper aluminum cleaner for welding can be the difference between fusion, and failure.

What Controls Bead Shape: Amperage, Voltage, Speed and Gun Angle

Every bead you lay is a physics problem solved in real time. Heat goes in, metal melts, the puddle freezes behind it, and the finished profile records four variables: current, voltage, travel speed, and gun or electrode angle.

Amperage (or Wire Feed Speed): The Penetration Dial

Amperage controls how deep you burn. In GMAW you rarely dial amps directly: wire feed speed (WFS) sets them, since faster feed means more wire melting into the puddle and more current drawn through the arc. Push WFS up and you get deeper penetration, a wider bead, and more heat in the plate. Drop it too far and the wire stubs instead of melting, or the bead rides on top of the joint.

For a starting point, Miller publishes a simple rule of thumb: 0.001 in (0.025 mm) of material thickness equals 1 ampere of welding current. So 0.25 in (6 mm) steel starts around 250 amps, adjusted for position, joint type, and travel speed (Miller’s GMAW guidelines). SMAW follows the same logic: thicker electrode and plate mean more amps, and a tall, narrow bead fused poorly at the toes usually indicts low amperage.

Voltage: Width and Height

Miller’s guidance is blunt: voltage controls the height and width of the weld bead. Too little and the arc runs short, the puddle piles up tall and narrow, and wire stubs in spattery, unstable transfer. Too much and the arc lengthens and wanders, the puddle flattens, and you get spatter plus a sloppy wide profile that struggles to tie into the toes. In SMAW the same rule reads as arc length: a long stick arc hisses and spatters, a tight one crackles cleanly.

The trick is matching voltage to WFS, not chasing one number. Treat manufacturer charts for wire diameter and transfer mode as starting points, then adjust for what the puddle tells you.

Travel Speed: The Cross-Section Control

Travel speed decides how much metal lands per inch of joint. Too slow and the bead balloons: wide, high, over-reinforced, and soaked with excess heat that widens the heat-affected zone and invites distortion. Too fast and the bead narrows, penetration drops, and the toes fail to fuse. The right speed wets the puddle out to the toes without outrunning you, leaving a smooth, slightly convex profile with uniform ripples.

Stickout and Gun Angle: The Fine Tuning

Miller lists five factors that shape a GMAW bead: gun angle, direction of travel, electrode extension (stickout), travel speed, and base metal thickness — plus WFS and voltage. Normal gun angle is 0 to 15 degrees from perpendicular. Work angle sets symmetry (tilt too far in a fillet and the bead favors one leg); travel angle sets penetration. Drag generally gives deeper penetration and a narrower profile than push, which lays a wider, shallower bead — handy on thin material and aluminum, where our Aluminum MIG Welding: The Complete Practical Guide covers technique in depth.

Contact tip-to-work distance matters more than most beginners realize. A short stickout increases penetration; a long stickout reduces it, because more of the wire preheats before the arc and current density drops. Keep it short and steady — roughly the wire diameter the chart calls for — and don’t let it drift as the puddle progresses.

Symptom, Cause, Fix: A Field Diagnostic List

• Tall, narrow bead with poor toe fusion → amps/WFS too low or travel too fast → raise amps or WFS and slow slightly.
• Wide, flat, spattery bead → voltage too high or arc too long → reduce voltage, tighten arc.
• Wire stubbing into the puddle → voltage too low for the WFS → raise voltage or reduce WFS.
• Excessive spatter with unstable arc → wrong polarity, bad gas flow, or voltage mismatch → check polarity, gas line, parameters.
• Bead favoring one side of a joint → work angle off center → return to perpendicular.
• Shallow penetration on thick plate → stickout too long or angle too steep → shorten stickout, ease angle to 0-15°, raise current.
• Heat cracks or burn-through on thin stock → too much current or slow travel → drop amps and speed up.

Cleaning sits underneath all of it: rust, oil, and mill scale distort arc behavior just as surely as a bad setting, which is why prep guides like Aluminum Cleaner for Welding: How to Prep Aluminum Right obsess over surface condition. Dial in the machine, control the angle, and the bead follows.

Reading a Bead: Good Characteristics vs Common Bead Defects

Once the slag comes off, the cheapest inspection in any shop is your own eyes and a flashlight. Visual inspection is the first acceptance gate in structural work, and everything downstream, from bend tests to radiography, is built on it. Reading a bead well is the difference between fixing a problem at pass three and finding it after the joint is boxed in.

What a Sound Bead Actually Looks Like

A healthy bead gives you the same signals every time:

• Uniform, evenly spaced ripples from start to finish.
• Consistent width along its length, with no swelling in the middle or tapering at the ends.
• Toes that blend smoothly into the base metal with no visible notch or sharp re-entrant corner.
• A clean face: no fused spatter balls, no drag marks, no pinholes, no trapped slag.
• A moderate crater at arc-out, slightly dished but filled rather than hollow.
• Full tie-in where the bead merges into the previous pass or the parent metal, with no step or cold edge.

Underneath, that bead should show complete fusion to the sidewalls and the penetration the procedure calls for, which bend tests or volumetric testing confirm rather than your eyes. Appearance is a proxy, never a proof. A glassy, picture-perfect bead on a contaminated plate can be a textbook lack-of-fusion failure dressed up for inspection.

Discontinuity vs. Defect: The Distinction That Matters

The AWS welding glossary defines a discontinuity as an interruption of the typical structure of a weld, and it is not automatically a defect. It becomes one only when it exceeds the range the applicable code permits. That distinction decides whether a small crater indication calls for a repair procedure or simply closer monitoring.

Kobelco’s weld imperfections guidance makes the split practical, grouping surface irregularities like uneven ripples, undercut, overlap and underfill apart from discontinuities proper like porosity, slag inclusions, lack of fusion and cracks. You catch the first group by eye; the second often needs low-angle light, dye penetrant or volumetric testing.

Surface Irregularities You Can See

• Undercut: a groove melted into the base metal along the toe that the filler never filled. It is a stress riser, which is why visual acceptance criteria cap it at 1/32 in (1 mm) deep.
• Overlap (cold lap): weld metal rolling over the base metal without fusing to it, usually from travel too slow, arc too long, or a gun angle that pushes metal where the pool will not take it.
• Underfill: the bead face sits below the adjacent base metal because not enough filler was deposited.
• Excessive reinforcement: an overbuilt proud cap. It does not make the joint stronger; it adds a thickness transition that concentrates stress.
• Craters and hollow craters: shrinkage voids at arc-out. Back up over the crater, use the crater-fill function, or expect a crack later.
• Waviness and uneven ripples: inconsistent travel speed, arc length swings, or an unsupported hand. Out-of-position work magnifies every tremor.
• Spatter: usually a parameter symptom, caused by wrong polarity, excessive voltage, wet electrodes, or an arc that is too long.

Discontinuities That Hide Below the Surface

What you see	What it usually is	Typical cause
Pinholes or worm tracks	Porosity	Contaminated metal or filler, moisture, lost shielding gas, drafts
Glassy or stony pockets between passes	Slag inclusions	Slag left by an incompletely cleaned pass
A seam with no visible fusion line	Incomplete fusion	Cold pool, travel too slow, wrong work angle
Root never joined	Lack of penetration	Insufficient amperage, gap too tight, electrode too large
Melted-through hole at the root	Excessive penetration / burn-through	Amperage too high, travel too slow, gap too open
Sharp, branching line	Crack	High restraint, hydrogen, rapid cooling, crater shrinkage

Cleanliness deserves special emphasis. On aluminum, porosity is nearly always a preparation failure: the oxide layer and the moisture it holds are the gas source. A disciplined aluminum cleaning routine before welding eliminates more porosity than any parameter change ever will.

And then there are cracks. Acceptance criteria permit no cracks of any size, in any location, at any stage of inspection. Everything else on this list is negotiable within stated limits. A crack is not.

How to Build the Habit

Read every bead before you clean the next joint. Lay a bead, chisel and brush it, then trace the toes with a flashlight held at a low angle so shadows reveal any notch your eye would miss. Name the defect out loud when you find one. Saying “that’s undercut from too long an arc” turns a rejected coupon into a lesson instead of a loss.

Troubleshooting Bead Problems: Causes and Corrective Actions

Nothing derails a weld day faster than a bead that keeps failing for reasons you cannot see. The useful question is never who messed up, but which variable moved. Bead problems trace back to five things: shielding, cleanliness, machine settings, technique, and body position. Diagnose them in that order, change one variable at a time, then run a fresh bead and compare. The list below follows the order most inspectors and supervisors use on the shop floor.

Excessive Spatter

Probable causes: amperage too high for the wire or electrode, arc length too long, wrong polarity, dirty or rusty base metal, a worn contact tip, arc blow from a badly placed ground clamp, or a gas mix carrying too much CO₂.

Corrective actions: bring amperage or wire feed speed back to the chart for the plate thickness, keep the arc short (on SMAW that means nearly dragging in the puddle), clean a couple of inches either side of the joint, replace the tip, and move the ground so the arc stops wandering. Anti-spatter spray and grinding remove the evidence, but they never fix the cause.

Porosity

Pores are gas bubbles frozen into the bead, and they come from the atmosphere, the material, or the parameters. Miller’s GMAW guidelines list inadequate shielding gas coverage, wrong gas, dirty wire, dirty workpiece, and wire extending beyond 1/2 in (13 mm) from the nozzle. Kobelco’s defect guide adds rust, oil, paint, moisture in coatings or flux, low gas flow, strong wind, and excessive amperage or arc length.

Corrective actions: brush the joint bright, check gas connections for leaks, set flow to the manufacturer’s spec instead of guessing, shorten stickout, and back the heat off. Drafts matter more than most welders expect, so shield the joint before you strike the arc. On aluminum, where oil and the oxide film hide moisture, the prep routine in aluminum cleaning prep is the cheapest porosity insurance available, and gas trouble surfaces fast in aluminum MIG welding, because the puddle gives far less warning than steel.

Incomplete Fusion

Probable causes: bead laid on the crown of the previous pass instead of at its toe, travel speed too fast, weave wider than the heat can fill, work angle pointing away from the joint corner, or settings too cold for the gap.

Corrective actions: place each stringer in the proper location, adjust the work angle so the arc points into the joint corner, and when weaving, hold the arc momentarily on the groove side walls so the puddle wets into them rather than floating past. This is the corrective sequence Iowa DOT and manufacturer guidance repeat for groove work. Then slow down: a bead laid in a hurry never has time to tie in.

Lack of Penetration

Probable causes: insufficient current, root opening too tight or uneven, travel too fast, stickout too long, arc pointed at the middle of the joint instead of the root, or a weave too wide for the root to get focused heat.

Corrective actions: raise amperage within the WPS range, verify the root gap and land, drag rather than push on a butt root, shorten stickout, and put a small stringer where the root needs it. A slight increase in travel time over the root often does more than another 20 amps.

Excessive Penetration and Burn-Through

Probable causes: too much current for the material, travel speed too slow, root gap too wide, or a dwell in one spot while you reposition your hands.

Corrective actions: reduce amperage or wire feed speed, speed up travel, close the root gap, and step tacks in so the gap stays controlled as the joint heats. On thin sheet, drop to a smaller wire or electrode diameter rather than compensating with speed alone.

Waviness of Bead

Probable causes: an unsupported hand, travel speed that speeds up and slows down, a weave wider than your control, or an awkward body position that forces you to reach.

Corrective actions: the standard fix is to support the hand on a solid surface or use two hands. Rest the forearm, position yourself so your whole body moves with the arc instead of stretching at the end of the joint, and shorten the weave until the width stays even. Consistent speed matters as much as consistent arc length.

Distortion

Probable causes: excessive heat input, too many passes, wide weave beads, poor weld sequencing, missing tacks, or an oversized root gap that pulls shut as it cools.

Corrective actions: favor stringers over wide weaves to cut heat input, alternate sides of the joint, use back-step and skip sequences, brace and clamp the assembly, and balance every pass on one side with a matching pass on the other where the design allows.

Crater Cracks

Probable causes: arc broken while the crater is still solidifying, travel speeding up at the stop, current not reduced at termination, or a crater left unfilled where the next bead ties in.

Corrective actions: at the end of the bead, back up over the crater and pause until it fills, or taper current for the last inch using the machine’s crater feature. On gas-shielded processes let post-flow cover it. Never break the arc mid-crater, and never start the next pass on top of an unfilled one.

Work the list in the same order every time: shielding, cleanliness, parameters, angle, speed, body position. Fix one variable, run one bead, then look at it under a light. What changes between beads tells you more than any single bead ever will.

Bead Acceptance Criteria and Inspection: What Codes Actually Require

A bead can look like a stack of dimes and still fail. That is the uncomfortable truth every welder learns eventually, and it is why acceptance criteria exist: they turn “looks good” into a number an inspector can measure. Knowing those numbers before you strike an arc is the difference between welding to a standard and welding to a hope.

Visual Inspection Is Always the First Gate

Every inspection sequence starts with the naked eye, a flashlight, and a weld gauge. Visual examination (VT) is the cheapest, fastest test there is, and it is the gatekeeper for everything else. Under AWS D1.1, if a test weld fails visual examination, the qualification test is over. No guided bend tests, no radiography, no ultrasonic testing. The welder simply does not qualify, and the shop re-tests after retraining. Visual criteria are that serious, which is why inspectors check reinforcement height, undercut depth, crater fill, and surface cracks before anything else happens.

The general visual checks a welder can self-apply are simple:

• No cracks anywhere, including crater cracks at arc termination.
• No lack of fusion visible at the toes or along the length.
• Undercut within limits, measured with a fillet weld gauge rather than estimated.
• Reinforcement not excessive and tapering smoothly into the base metal.
• Craters filled to the full cross-section of the bead.

Qualification Coupons vs Production Welds: Two Different Rulebooks

This is where most welders get tripped up. AWS D1.1 Clause 6.23 governs the performance qualification coupon — the test plate you weld to prove you are qualified. Its visual criteria are deliberately strict:

Criterion	Clause 6.23 Coupon	Table 8.1 Production (typical)
Cracks	None permitted	None permitted
Lack of fusion	None permitted	None permitted
Undercut	≤ 1/32 in (1 mm)	Up to 1/16 in (2 mm) in some conditions
Face reinforcement	≤ 1/8 in (3 mm)	≤ 1/16 in (1.5 mm) typical for plate
Craters	Filled to full cross-section	Filled to full cross-section

Read that carefully: the coupon limits are tighter than the production limits. A bead with 1/16 in of undercut might be acceptable in the finished structure under Table 8.1, yet it fails the qualification test outright. Weld your test plate to production tolerance and you will likely fail. Weld it tighter than production requires and you leave yourself margin.

Root Condition, Porosity and the Rest of the Checklist

Root criteria matter as much as the visible face. D1.1 limits root concavity (a sucked-through root on the back side), permits a defined amount of melt-through in groove welds, and restricts porosity by size and distribution. A root that looks rough from the back side can fail before an inspector ever looks at the cap. The same applies to slag inclusions and internal lack of fusion, which no amount of visual skill can detect — that is where NDT comes in.

Gages, Bend Tests and NDT Substitution

Fillet weld gages are the welder’s own quality control: a simple combination gauge measures leg length, throat, and undercut in seconds, and every welder should carry one. Beyond visual, qualification normally requires guided bend tests, which physically cut and bend test specimens to expose lack of fusion or porosity that was hidden. Radiographic testing (RT) may substitute for bend tests in qualification, with one important exception: GMAW short-circuiting transfer mandates guided bend testing, because RT cannot reliably detect the lack-of-fusion defects that short-circuit parameters can produce. UT has its own substitution rules depending on the application, and some codes prohibit substituting RT/UT for welds made by certain processes.

Qualification itself falls into two camps that people confuse constantly: welder qualification proves the individual can produce sound welds under the WPS, while certification is an administrative acknowledgement of that qualification. The AWS Welding Digest explainer on performance qualification and certification is worth reading if your shop is arguing about which is which.

If you want to see how visual acceptance criteria are framed outside structural steel, the compiled weld quality standards reference from Portland Community College collects several side by side, and defect imagery is catalogued in the Kobelco welding defect handbook. For process-specific bead work on aluminum, our Aluminum MIG Welding: The Complete Practical Guide covers the same acceptance logic applied to GMAW on aluminum, and process control under strict standards is examined in Aerospace Welding: Processes, Standards, and Careers Guide.

The takeaway is simple. Learn the numbers, carry a gauge, weld tighter than the limit, and treat visual inspection as the pass/fail gate it actually is. Everything else — bends, radiography, ultrasonics — only happens after your bead survives the first look.

Bead Technique by Process and Position: Practice Drills That Work

The bead you lay in the flat position on a clean plate is the easy version. What separates a hireable welder from a hobbyist is the ability to reproduce that same bead in a corner, overhead, on 3/8-inch plate, and on the fourth hour of a shift. Process matters here, position matters more, and deliberate practice matters most.

Process-by-Process Bead Technique

SMAW. Stick is still the baseline skill. An E6011 runs on a fast, aggressive arc for root passes and dirty metal, and it rewards a slightly longer arc and a quick travel speed. An E7018 wants the opposite: a short, tight arc, a slight drag angle, and steady speed so the slag stays fluid and lifts cleanly behind you. Both favor stringers. If you are just starting out, the advantages of stick welding are worth understanding, because the process teaches arc length control that transfers to every other process.

GMAW. Transfer mode changes everything about the bead. Short-circuit transfer cycles the wire into the puddle 90 to 200 times per second, which keeps heat low enough to weld thin sheet in any position, at the cost of lower deposition and more spatter. Spray transfer delivers high deposition, excellent fusion and a smooth bead appearance, but it is limited to flat and horizontal fillet positions on material 1/8 inch (3 mm) or thicker. On aluminum, prep and heat control dominate technique, which is why aluminum MIG welding leans on clean material, short stickout and faster travel.

FCAW. Self-shielded wire behaves like a hotter stick electrode: it wants a drag angle, slower travel, and disciplined interpass cleaning. Gas-shielded flux core runs cleaner and lets you dial heat down, but it is draft-sensitive.

GMAW/GTAW on nonferrous work. TIG rarely needs a weave at all. On most butt joints a straight stringer with a controlled dab of filler produces full fusion without the risk a weave carries. For aluminum specifically, surface prep is half the bead, which is where aluminum cleaner for welding earns its place.

SAW. Submerged arc runs long stringer beads with high current and consistent travel speed; the flux hides the puddle, so you read bead width and edge tie-in instead of ripples.

Position, Sequence and Why Stringers Win Grooves

The Iowa DOT IM 558 guidance recommends using the stringer bead technique wherever possible for groove welds, and progressing upward with a back-step sequence in vertical welding. The reasoning is practical: stringers put less heat into the joint, keep the HAZ narrow, and reduce distortion, while back-stepping means each bead is welded toward already-supported metal, which limits warping.

Position changes the game:

• Flat is where spray transfer and wide weaves belong; gravity helps the puddle wet out.
• Horizontal needs stringers stacked from the bottom up so the top of the puddle does not sag.
• Vertical-up favors a narrow weave with a short arc; the puddle shelf you create supports the next increment.
• Overhead is stringer territory: fast travel, minimal weave, and small beads to keep the puddle from dripping.

Out-of-position work is the one place a controlled weave genuinely helps, because the side-to-side motion lets you freeze the edges before gravity pulls the center down. Our all position welding rod guide covers electrode choices for those situations.

A 5-Day Bead Drill on Plate

1. Day 1: Stringer beads on 1/4-inch plate, flat. Goal: constant width, no tie-in gaps. Scribe width lines and stay inside them.
2. Day 2: Same beads, but hold ripple spacing constant. Count ripples per inch and repeat it.
3. Day 3: Tie-in practice. Lay a bead, clean it completely, then run the next bead so its edge overlaps the previous toe by roughly half a bead width.
4. Day 4: Position rotation. Run the same bead flat, horizontal, vertical-up and overhead. Adjust work angle and travel speed, not ambition.
5. Day 5: Back-step sequence across a plate. Segment the joint into 1.5 to 2-inch lengths, weld each backward toward the start, clean between every segment.

Practice safely or the drills cost you more than they teach. Wear a correctly shaded helmet, flame-resistant jacket, gloves, hearing protection and steel-toe footwear, and control fumes with ventilation or local exhaust. OSHA addresses welding fume and gas control under 29 CFR 1910 Subpart Q for general industry and 29 CFR 1926 Subpart J for construction. Wind screens matter outdoors: shielding gas loss is the fastest route to porosity no amount of technique will fix.

Common Bead Mistakes, Myths, and How to Avoid Them

Most bad beads don’t come from bad welders. They come from habits that nobody ever corrected: weaving because it looks professional, running a long arc because it’s easier to see, capping a shift before the crater is filled. Here are the mistakes that cause the most rework, and the myths that keep them alive.

The Ten Habits That Ruin an Otherwise Good Bead

• Weaving by default. If the joint doesn’t need width, run stringers. Unnecessary oscillation raises heat input and widens the heat-affected zone for no benefit.
• Long arc length. Extra arc length drops shielding coverage, lifts spatter, and thins the bead. Keep the electrode or contact tip close to the work.
• Skipping interpass cleaning. Slag inclusion is most often caused by improper cleaning, improper electrode manipulation, or poor bead placement. Chipping one pass and welding the next over leftover slag is the single most common cause of a rejected gouge-out.
• Traveling too fast. Speed starves the bead of metal, producing a narrow, high-crowned profile with poor tie-in and, on thin material, lack of fusion at the toes.
• Chasing appearance over fusion. A mirror-smooth stack of dimes with a cold root is a rejection with good lighting.
• Ignoring crater termination. Back off the current or fill the stop. Craters shrink as they cool and open into crater cracks.
• Welding over paint, rust, oil, or mill scale. Contaminants burn into the arc and come out as porosity or inclusions. On aluminum, prep is even less forgiving, which is why dedicated aluminum cleaner and pre-weld prep matters so much.
• Wrong gun or work angle. An off-angle gun pushes the bead off center, undercuts one side, and builds the other. Correct the angle before you correct the parameters.
• Excessive reinforcement. More metal is not more strength. Reinforcement above the limit creates a notch at the weld toe where fatigue cracks start. Under AWS D1.1 visual criteria, reinforcement over 1/8 in (3 mm) is not accepted.
• Arc strikes outside the weld area. Stray arcs gouge the base metal and act as crack initiators; they are not acceptable under common visual inspection criteria and must be ground smooth and re-examined.

Three Myths That Refuse to Die

“Weave welds are stronger.” Weaving doesn’t add strength; it adds width and heat. Strength comes from fusion, filler classification, and joint design. A wide weave over a cold root is weaker than two narrow stringers that actually melted the joint faces.

“More passes make a better weld.” Pass count only matters relative to heat input, interpass temperature, and cleaning. Twelve careful stringers beat six careless weaves, and sometimes one properly sized pass beats both.

“Grinding fixes defects.” Grinding hides surface evidence and can thin the reinforcement, but it doesn’t remove a subsurface lack of fusion or an internal crack. As Kobelco’s defect guide makes clear, some discontinuities are rejectable defects and others are tolerable discontinuities — and grinding doesn’t change the category.

Conclusion: What a Weld Bead Actually Is

Strip away the slang and a weld bead is simply a weld deposit produced by a single pass of a welding process, as worded in AWS A3.0. It has a defined anatomy — face, toes, root, reinforcement, throat — it is shaped by amperage, voltage, travel speed, and angle, and it is judged against written acceptance limits rather than opinion. Everything in this article follows from that definition: stringer versus weave is a choice about heat, pass sequence is a plan for filling a joint, and every defect listed here is a failure to control one of those variables. Look at a bead the way an inspector does, from the toes inward, and the story of how it was made reads clearly.

Checklist for Consistent Beads

1. Clean the joint, and clean again between passes.
2. Set amperage and voltage to the WPS, not to habit.
3. Pick stringer unless the joint genuinely needs width.
4. Hold a steady arc length, work angle, and travel speed.
5. Watch the toes tie in, not the center of the bead.
6. Control interpass temperature; don’t let the plate run away.
7. Fill every crater before you break the arc.
8. Stop and correct profile before the cap goes on.

Run that list on every plate, and the bead you hand the inspector will look good and be sound — which, as the apprentice with the hidden undercut learned, is the only combination that counts.

Frequently Asked Questions

What is the definition of a weld bead in welding?

A weld bead is a weld deposit produced by a single pass of a welding process. It can be narrow (little side-to-side motion) or wide (heavy transverse oscillation), and a completed weld may be built from many beads stacked as root, fill and cover passes.

What is the difference between a stringer bead and a weave bead?

AWS A3.0 defines a stringer bead as deposited without appreciable transverse oscillation, while a weave bead is made with side-to-side oscillation. Stringers keep heat input and heat-affected zone width lower; weaves cover more area per pass but add heat and slow travel speed.

How wide should a weld bead be?

For SMAW, welders commonly run stringer beads about two to three electrode diameters wide and weave beads roughly four to six diameters wide, and many textbooks advise keeping a weave under about twice the electrode diameter. Always defer to your WPS and the governing code, which may cap weave width.

Why does my weld bead look lumpy and uneven?

Uneven ripples and bead waviness usually come from irregular travel speed, arc length that is too long or too short, wrong amperage, or an unsteady hand. Slow down deliberately, rest your hand or torch on the workpiece, and verify your settings with a test bead before running the joint.

What causes porosity in a weld bead?

Porosity is gas trapped as the bead solidifies. Common causes are lost or low shielding gas, drafts, dirty or oily base metal, damp electrodes, too long an arc, and wire stickout longer than about 1/2 in (13 mm) from the nozzle.

How much reinforcement and undercut does a bead allow?

Under AWS D1.1 visual criteria, groove weld reinforcement must be flush to 1/8 in (3 mm) high and undercut must not exceed 1/32 in (1 mm) deep, with zero cracks permitted. Qualification coupons are held to the stricter 1/32 in undercut limit while production work can allow up to 1/16 in under certain conditions.

Should I weave or use stringer beads to fill a groove weld?

Stringer beads are generally preferred for groove fills because they minimize heat input and give more consistent fusion. Weaving is useful for open roots, bridging gaps, out-of-position welds and widening a cover pass, provided you dwell at the edges and respect code weave-width limits.

How can I practice to get consistent beads?

Run beads on flat plate with consistent settings, aiming for uniform width, even ripple spacing and clean tie-in at both toes. Focus on travel speed, a short steady arc, correct 0-15 degree gun or work angle, and stopping technique that fills the crater before releasing the arc.

Does a visually perfect bead guarantee a strong weld?

No. Appearance only covers the surface — lack of fusion, slag inclusions and root defects are hidden beneath it. Visual inspection is the mandatory first check, but codes often require bend tests or radiographic/ultrasonic testing to confirm soundness.