Welding Symbol for Stitch Welding: How to Read 2-6

A fabricator taps the print with a gloved finger and asks the new welder, “So how long is each weld, and how far apart?” The drawing says only 2-6 next to a small triangle, and two people can read that same symbol and build two completely different joints. That tiny pair of numbers controls how much weld goes into the part, how much it distorts, and whether it passes inspection.

Why the Stitch Weld Symbol Trips Up So Many Welders

The print lies flat on the bench, still smelling like the plotter. Next to a small fillet triangle, someone has typed 2-6. One welder looks at it and says, “Two inches of weld, then a six-inch gap.” The other one shakes his head. “No, two inches of weld, and the next one starts six inches from the start of the first.” Both men are experienced. Both are sincere. And if nobody settles the question before the first arc is struck, the shop is about to build two different parts from the same drawing.

Here is the answer up front. A stitch weld symbol is an intermittent weld callout. In most cases it is an ordinary fillet weld symbol with two dimensions written to the right of the triangle, separated by a dash: the length of each weld segment, then the pitch. Those numbers sit on the reference line, and the line tells you which side of the joint gets the weld. That is the whole idea. Everything else in this article is detail layered on top of that one sentence.

“Stitch Weld” Is Shop Talk. “Intermittent Weld” Is the Standard Term.

Part of the confusion is vocabulary. On the floor, people say stitch weld, stitch welding, skip welding, or intermittent welding, and they usually mean the same thing. Open WA’s AWS A2.4 conventions, pitch is measured center-to-center, not edge-to-edge. That single detail is where most shop-floor confusion begins, because the gap a welder sees on the part is not the number written on the print.

Segment Length: The Weld You Actually Lay Down

Segment length is the finished length of one bead, measured from the start of the weld to the end of the weld along the joint. On a 2-6 callout, the 2 means 2 inches of deposited weld. It is a real dimension on the part, and it is what an inspector will put a tape against.

Two practical points about length:

• It is measured along the joint axis, not around the weld face.
• It applies to each segment, not to the total weld in the joint.

So a joint made with ten 2-inch segments at 2-6 does not have a 2-inch weld in it. It has twenty inches of weld spread over roughly sixty inches of joint.

Pitch: The Number Everyone Misreads

Pitch is the center-to-center spacing. If the first segment is centered at 0 inches, the next one is centered at 6 inches. The third is centered at 12 inches, and so on down the joint.

Here is the arithmetic that matters. With a 2-6 callout:

• Pitch: 6 in.
• Segment length: 2 in.
• Unwelded gap: 6 − 2 = 4 in.

That 4-inch gap is what the welder physically skips. But 4 does not appear anywhere on the drawing. The symbol never tells you the gap directly — it tells you the length and the centers, and the gap is a subtraction you do yourself.

When Only One Number Appears

A length can stand alone; a pitch cannot. If only one dimension appears to the right of the weld symbol, it is the weld length, not the pitch. That callout defines a weld shorter than the full joint, and its location is dimensioned separately somewhere else on the drawing.

This is common on short joints, on welds that stop short of a corner, and on details where the engineer wants a specific length of weld in a specific place. Reading a lone number as a pitch is a serious error — it turns a defined weld into an undefined pattern.

Counting Segments on a Real Joint

The segment count follows from the joint length and the pitch, but where the pattern starts changes the answer. Take a 24-inch joint at 2-6, with the first segment starting flush at one end:

• Segments begin at 0, 6, 12, and 18 in.
• That is four segments, but the last one runs from 18 to 20 in.
• A fifth segment at 24 in. would land entirely off the joint.

So a 24-inch joint gets four segments — unless the drawing requires both ends welded. If both ends must carry weld, the pattern has to be laid out so a segment lands at each end, which usually means the intermediate spacing compresses slightly. That is a conversation for the engineer, not a decision to make quietly with a grinder.

A 36-inch joint at 2-6 gives segments starting at 0, 6, 12, 18, 24, and 30 in. — six segments, with the last one ending at 32 in. and 4 in. of joint left bare at the far end. Whether that bare end is acceptable depends entirely on the drawing and the governing code.

Common Callouts and What They Produce

Callout	Segment Length	Pitch (C-to-C)	Unwelded Gap
2-4	2 in.	4 in.	2 in.
2-6	2 in.	6 in.	4 in.
3-9	3 in.	9 in.	6 in.
1 1/2-4	1.5 in.	4 in.	2.5 in.
50-150 mm	50 mm	150 mm	100 mm

Notice how aggressive the duty cycle gets as the numbers spread. A 1 1/2-4 pattern puts roughly 37 percent of the joint under weld, while 3-9 puts about 33 percent. A 2-6 callout is roughly a third welded and two thirds open. If someone tells you a stitch weld is “about half,” they are guessing.

Metric Drawings Work Exactly the Same Way

Millimeters change the units, not the logic. A 50-150 mm callout means 50 mm of weld with 150 mm between centers, leaving a 100 mm gap. Segment counts divide out the same way: a 1200 mm joint at 50-150 gives segments centered at 0, 150, 300, and so on, up to 1050 mm — eight segments, with the last one ending at 1100 mm.

The trap on metric drawings is mixing scales. A welder used to inches who glances at “50-150” and assumes sixteenths will lay down a completely wrong pattern. Read the drawing units before you touch a tape measure.

Whatever the process — whether you are running a structural fillet or working through something like aluminum MIG welding on thin sheet — the length and pitch relationship is identical. Only the deposition behavior and heat spread change.

Tolerances, Drift, and Why Centers Beat Gaps

Real joints are not perfect. A tape hooked at one end and walked down a 40-foot beam accumulates error with every reposition, and a print marked in chalk smears. This is the cumulative drift problem: small errors at each segment compound until the far end of the joint bears no resemblance to the drawing.

The fix is to work from centers and to work from a fixed datum. Mark segment centers with a soapstone line or a punch mark, reference every one back to the same end of the joint, and re-measure the accumulated total against the drawing about every ten feet. If the drift exceeds a sensible field tolerance, stop and correct before laying more weld, because correcting twenty feet of pattern is far cheaper than cutting out one.

ISO 2553 complicates this further. The National Board notes that ISO defines pitch as the clear distance between segments rather than the distance between centers. Under that definition, a 2-6-style callout in a metric ISO drawing does not mean what an AWS-trained welder assumes. The gap and the pitch are the same number, and the centers fall further apart.

For a deeper look at how the symbol itself is assembled — arrow side, reference line, tail, and the placement rules that sit on top of these numbers — see our breakdown of the fillet weld symbol anatomy. And when the pattern shifts from aligned to offset, the half-pitch convention comes into play; that is where staggered intermittent welds get their geometry.

Length first, pitch second, centers not gaps. Those three rules will decode any stitch weld callout you meet, whether it is written in inches, millimeters, or something in between.

Chain, Staggered, Both-Sides, and Other Symbol Variations

Length and pitch tell you how much weld goes down. Placement tells you where it goes. Once you understand both, the symbols on a print stop looking like code and start reading like a set of instructions. This section covers the variations you will actually run into: one-sided patterns, chain and staggered layouts, all-around and field callouts, and a few weld types that get mistaken for stitch welds but are not the same animal at all.

Single-Sided Intermittent Fillet

The simplest version is one triangle, one size, one length-pitch pair, placed below the reference line. That means intermittent fillets on the arrow side only, nothing on the other side. You weld your segments along one toe of the joint and stop. No offset, no mirror image, no second pass on the far side. Most shop drawings for stiffeners, gussets, and light brackets use this pattern because it is easy to inspect and easy to fixture.

Chain Intermittent: Segments Face to Face

A chain intermittent fillet weld puts segments directly opposite each other across the joint. On the drawing, you see a triangle both above and below the reference line, with the size and the length-pitch pair written on both lines. Both symbols sit at the same position along the line, because the welds physically line up: the segment on the near side and the segment on the far side start and stop together.

Chain patterns concentrate heat in the same cross-section twice in quick succession. On light material, that is exactly what you do not want. On heavier plate, though, chain is fast, simple to lay out, and easy for an

Stitch Weld vs Continuous, Seam, Tack, and Skip Weld

Walk through any fab shop and you will hear the same word used three different ways before lunch. “Put a stitch on it” might mean a short intermittent weld, a quick tack to hold alignment, or a temporary bridge while the fitter adjusts the part. On the drawing, those are different requirements. Mixing them up is how a joint ends up with too little weld, too much heat, or a leak that nobody expected.

The confusion is understandable because the terms overlap in everyday speech. They do not overlap in a weld symbol or a procedure. Here is the clean version.

The Five Terms, Defined Without Shop-Slang Fog

A continuous weld runs the full length of the joint. There are no planned gaps. On a fillet symbol, a continuous weld usually appears as a triangle with a size but no length-and-pitch pair to the right.

A stitch weld is a weld made in segments with gaps between them. The standards term is intermittent weld. AWS terminology treats “stitch weld” as a nonstandard shop term, which is exactly why a print may say either one. On the symbol, the segment length and pitch sit to the right of the fillet triangle, separated by a dash. If you need a refresher on the basic symbol layout, Miller’s guide to reading and understanding weld symbols is a useful starting point.

A seam weld is continuous and is used where a leak-tight or fluid-tight joint is required. It is often made by resistance seam welding, where overlapping nuggets form a sealed line. A seam weld is not an intermittent weld with smaller gaps. It has no gaps by definition.

A tack weld is a temporary locating weld. It holds parts in alignment until the real weld is made. It is not a substitute for the specified weld size or length, and it is not a finished joint.

A skip weld is shop slang with two common meanings: an intermittent weld, or a welding sequence that skips around the part to balance heat and control distortion. Because the word can mean either, treat it as a question, not an instruction. Ask which one the drawing or procedure intends.

How the Terms Compare on the Floor

Term	What the drawing usually shows	Purpose	Typical use	Inspection focus	Common failure
Continuous weld	Fillet triangle with size only, or a groove symbol with no segment length	Full-strength or sealed joint	Pressure boundaries, fatigue details, tank shells	Size, profile, fusion, continuity	Excess heat and distortion on thin parts
Intermittent (stitch) weld	Triangle with length and pitch, such as 2-6	Reduce weld volume and heat input	Long fillet joints on frames, enclosures, stiffeners	Segment length, pitch, placement, crater fill	Short segments, drifting pitch, missed gaps
Seam weld	Often a note or resistance-weld symbol rather than a fillet callout	Leak-tight or fluid-tight joint	Tank shells, drums, thin sheet pressure boundaries	Continuity, penetration, leak test	Pinholes, skips, incomplete fusion
Tack weld	Usually a note such as “tack only,” not a finished weld symbol	Temporary alignment	Fit-up, fixtures, assembly	Size, cleanliness, location, removal if required	Crack initiation, interference with final weld
Skip weld	No standard symbol; depends on context	Either intermittent welding or a heat-balancing sequence	Distortion-sensitive assemblies	Confirm intent before welding	Wrong interpretation, uneven shrinkage

Why a Tack Weld Is Not a Free Segment

This is where a lot of otherwise good work goes wrong. A print calls for a 2-6 intermittent fillet. The fitter tacks the joint every few feet. Then the welder measures from tack to tack and treats those tacks as part of the specified segments. The result may look reasonable, but the weld is no longer what the drawing defines.

Tacks change the heat pattern, the restraint, and the inspection picture. In fatigue service, a small, rapidly cooled tack can act as a crack starter. In pressure service, tacks may need to be removed or fully fused into the final weld, depending on the procedure and the applicable code. The National Board and ASME pressure-vessel requirements are strict about weld quality for good reason. If the WPS does not allow tacks to remain, they come out. If they remain, they must be clean, sound, and treated as part of the weld, not as a shortcut.

Four Jobs, Four Correct Answers

Trailer frame crossmember: A long fillet joint may be specified as intermittent because full-length welding is not required by design and would add unnecessary heat. The welder still needs to place the segments deliberately and keep tacks out of the measurement.

Handrail post: A stainless handrail is a corrosion detail as much as a structural one. An intermittent weld around a post base can leave crevices that hold moisture and bleed rust onto the surface. That is often a case for a continuous weld, a sealant, or a design change, not a stitch weld.

Sheet metal enclosure: Here, intermittent welds are often chosen to limit oil-canning and buckling. The same heat-control thinking applies to aluminum enclosures, and our guide to aluminum MIG welding covers the travel-speed and heat-input side of that problem.

Tank shell: A tank shell is a leak-tight boundary. It calls for a continuous seam weld or a continuous arc weld, not a stitch pattern. Replacing that with intermittent welding creates a controlled leak path by design.

The underlying rule is simple: the symbol tells you what kind of weld is required, and the code plus the WPS tell you whether that weld is allowed. A stitch weld is a design decision. It is not a production shortcut a welder can choose unilaterally, and turning a specified continuous weld into stitches is a nonconformance. For fillet-specific symbol details, Weld Guru’s breakdown of fillet weld symbols is a helpful cross-check.

Use the words precisely, and the drawing gets easier to read. Continuous means full length. Intermittent means planned segments. Seam means sealed. Tack means temporary. Skip means ask.

Why Engineers Call for Stitch Welds, and When They Refuse To

Walk through any fabrication shop and you’ll find two kinds of drawings. Some are welded solid, edge to edge, all the way down. Others carry those tidy little 2-6 callouts that leave big stretches of bare steel between short runs of weld. To a welder paid by the hour, the second kind looks like a break. To the engineer who signed it, it’s a carefully calculated trade — and one with strict limits. Understanding why that callout exists, and where it stops being legal or safe, is what separates a welder who follows the print from one who second-guesses it.

What Intermittent Welding Actually Buys You

Every arc you strike puts heat into the part. Heat expands metal, and as it cools and contracts, the part moves. Continuous welds down a long joint stack that movement up until a plate bows, a beam flanges out of square, or thin sheet turns into a potato chip. Intermittent welds break the heat input into doses. Instead of one long thermal cycle, the part gets a series of short ones with cooling time between, which is why stitch patterns are so common on long, slender, or thin-walled assemblies.

The engineering payoff comes down to a handful of connected benefits:

• Lower total heat input. Fewer arc-on inches means less expansion and contraction, so angular distortion drops and thin panels are less likely to buckle or oil-can.
• Less weld metal and arc time. A 2-6 pattern on a 10 ft joint deposits roughly a third of the filler a continuous weld would. That’s real savings in consumables, labor, and machine hours.
• Faster cooling and lower residual stress. Short segments cool quickly and lock in less locked-in stress than a long, hot bead.
• Balancing. On a symmetrical part — a built-up column, a frame, a stiffener on both sides of a web — the engineer can alternate sides and pull the part back and forth against itself instead of letting it drift one way.
• Straighter parts after welding. Less straightening means less post-weld flame work, pressing, or machining.

Those advantages are why intermittent welds show up on stiffeners, built-up members, sheet metal enclosures, and non-critical connections. They are a legitimate design tool, not a shortcut.

The Hidden Costs Nobody Puts on the Drawing

What the print doesn’t show is the labor on the other end of the equation. Every segment is a start and a stop, and every start and stop means a crater to manage, a tie-in to blend, and a spot that can crack if you snap the arc off cold. A 12 ft joint at 3-9 has more arc starts than a continuous bead by an order of magnitude, and each one is a chance for porosity, lack of fusion, or a ragged terminator.

There’s also the measuring. Somebody has to lay out centers, mark them, and keep checking as the joint grows, because pitch drifts. Small errors accumulate over a long run: start a quarter inch long on segment one and, twenty segments later, you can be inches off the pattern the engineer intended. That drift is exactly what inspectors catch with a tape measure. If you want a refresher on the layout math, our guide to aluminum MIG welding covers how heat and travel speed interact on thin sections, where stitch patterns earn their keep most often.

The Limits: Where Stitch Welds Get Refused

Honest engineering means knowing when an intermittent weld is the wrong answer. The same gaps that save heat create problems in specific service conditions.

• Leak-tight joints. Tanks, vessels, piping, ducts carrying liquids or gas — anything that must hold pressure or seal — needs a continuous weld. Segments simply cannot seal a joint.
• Corrosion-exposed surfaces. Every gap between segments is a crevice where moisture, salt, and debris collect and stay. Crevice corrosion starts there, and on stainless it often shows up as rust bleeding onto the surface. That’s why sanitary, marine, and food-contact work is usually continuous. Proper surface prep helps elsewhere; see our notes on aluminum cleaner for welding for how contamination drives corrosion.
• Fatigue-critical details. Each weld termination is a stress riser. Under repeated loading, segment ends become crack initiation sites, which is why bridge, crane, and dynamically loaded structures are treated very carefully.
• Code-restricted applications. Structural welding codes place conditions on where intermittent fillet welds may be used — minimum lengths, restrictions near certain details, and outright prohibitions in some cases. The governing code must be checked before anyone substitutes stitches for a continuous weld.

A Design Decision, Not a Welder’s Shortcut

Here’s the rule that matters most on the floor: reducing a specified continuous weld to intermittent segments is a nonconformance, full stop. It changes the strength, the stiffness, the corrosion behavior, and the fatigue life of the joint. If a welder decides the drawing calls for too much weld and thins it out to save time, that part is no longer built to the design — even if it looks tidy. If a callout seems wrong, the move is an RFI to the engineer, not a judgment call with a stinger in your hand.

If you’re welding a dissimilar or alloy joint where the engineer has to weigh distortion against corrosion, references like our Alloy 20 welding procedures guide show how much process selection affects the outcome.

Fume and Ventilation: The Safety Side of Starts and Stops

Intermittent welding changes exposure patterns as well as heat patterns. More starts and stops mean more arc time near the same spot, more flux or wire burn-off in bursts, and often a welder leaning closer to reposition. Under OSHA 29 CFR 1910.252, welding areas require adequate ventilation and control of fume exposure, and local exhaust at the arc is the preferred control. On stainless and other chromium-bearing metals, the hexavalent chromium standard sets a permissible exposure limit of 5 micrograms per cubic meter as an 8-hour time-weighted average, which is low enough that a short burst of welding in a poorly ventilated corner can matter.

Practically: keep the fume extraction positioned where the arc actually is, since stitch welding moves the arc along the joint, and don’t let a helper stand in the plume to hold a tape. For a broader look at controlling exposure, OSHA’s welding, cutting and brazing guidance is a good starting point.

The takeaway is simple. Stitch welds are a smart, deliberate answer to distortion and cost on the right joint, and a liability on the wrong one. Read the symbol, read the note, read the code, and let the design decide.

Welding a Stitch Weld Correctly: Setup, Sequence, and Inspection

A stitch weld is easy to draw and easy to get wrong on the floor. The symbol gives size, length, and pitch; your job is to repeat that pattern from the first inch of the joint to the last. Setup, sequence, and measurement do most of the work.

Read the WPS Before You Strike an Arc

Before touching the stinger or gun, read the WPS and confirm five values: fillet size, segment length, pitch, pattern, and process. Check that the procedure covers the thickness and position. A 1/4 in. fillet at 3-9 does not mean “run a 1/4 in. bead wherever it looks right.” It means 3 in. of weld, a 6 in. gap, and 9 in. from center to center. Confirm arrow side, other side, or both. If a value is missing, ask. The symbol is the contract; the WPS is the instruction sheet.

Know the minimum too. Many structural codes, including AWS D1.1, require each intermittent segment to be at least four times the weld size. For a 1/4 in. fillet, that is 1 in.; this welding textbook summary covers the rule. A project may add a larger minimum, so check the code and WPS.

Fit-Up, Tacking, and Marking Centers

Fit-up decides whether the joint can accept the specified fillet without ending up undersized or unequal. Set root opening and alignment, then tack so the joint cannot close or pull out of line. Put tacks where production welds will consume them, or remove them when the WPS says so. Never count a tack as a segment unless the procedure allows it.

Mark segment centers, not gaps. Centers are what the symbol defines; gaps are a result. On a 9 in. pitch, mark stations every 9 in. from a fixed datum, then mark half the segment length each side of every center. Measuring from one weld edge to the next invites cumulative drift. Pull the tape from the same datum and check the overall layout before welding.

Start, Stop, and Sequence

Each segment has two ends, so each one is a chance for a defect. Establish the arc, move into the joint, and hold a steady travel speed and angle. At the end, ease out and pause to fill the crater instead of snapping off. Filling the crater reduces crater cracks and shrink defects. The ends should also be full size, fused, and free of undercut. A segment that tapers to nothing is short even if the chalk mark says otherwise.

Use sequence to control heat. Backstep short segments against the direction of travel, alternate sides on double-sided joints, skip around a large part, and clamp where the WPS allows. These techniques spread heat. They do not excuse a short segment or a missed station.

Worked Example: 12 ft Joint, 1/4 in. Fillet at 3-9

A 12 ft joint is 144 in. Divide by the 9 in. pitch: 16 intervals. Starting with a 3 in. weld at one end gives 16 segments, each followed by a 6 in. gap, with 6 in. left at the far end. If the detail requires a weld at both ends, you need a 17th segment, and the final spacing closes up unless the engineer adjusts the layout. Confirm that end condition in writing. The 3 in. length clears the four-times-size minimum, but not the requirement to place segments correctly.

Inspection: Measure the Pattern, Not the Vibe

Check each segment with a fillet gauge, and measure length and pitch with a tape. Visual inspection must confirm segment length, pitch, and fillet size, not just overall appearance. Look for craters, undercut, spatter, missed segments, and tapered ends. Then measure cumulative drift from the datum at the last station. Record actual pitch and deviations. A neat row of beads can still be out of tolerance.

Troubleshooting Intermittent Welds

Symptom	Likely Cause	Fix
Segments too short	Rushed start or stop; trying to stretch the count	Mark full length, start on the line, fill the crater, check with a tape
Pitch drifting	Measuring from weld edges; tape sag; no fixed datum	Mark centers from a datum; verify cumulative spacing
Arc blow	Long arc; poor ground; magnetic field	Shorten the arc, move the ground, change angle or use backstep
Burn-through on sheet	Too much current; slow travel; poor fit-up	Reduce current, increase travel, improve fit or use a heat sink

On thin sheet, burn-through usually points to current, travel speed, fit-up, or heat input. For aluminum, start with Aluminum MIG Welding: The Complete Practical Guide before you chase the problem with a faster hand.

Code Talk: AWS A2.4, AWS D1.1, ISO 2553, and Drawing Notes

A stitch weld symbol is only one part of the instruction. The symbol tells you what the joint should look like. The project code says whether that weld is permitted. The WPS says how to make it. Miss one and a perfectly drawn symbol can still produce a rejected part.

Three Documents, Three Different Jobs

AWS A2.4 is the symbol rulebook. It defines the arrow, reference line, tail, triangle, and dimension placement. Think of it as the grammar of the drawing.

Project codes decide when those symbols may be used. AWS D1.1 governs structural steel, D1.2 covers aluminum, and D1.3 addresses sheet steel. Each code sets its own limits, and D1.1, for example, includes requirements that control whether and where intermittent welds are acceptable.

For pressure-retaining work, ASME Section IX governs qualification of welding procedures and welders. It does not usually dictate stitch spacing; it ensures the procedure and the person running it have been qualified for the job.

That division matters. A symbol can say “2 in. long on 6 in. centers,” while the project code says those welds are not allowed on a particular member. The WPS supplies amperage, voltage, travel speed, preheat, and filler. The symbol says what; the code and WPS say whether and how.

AWS A2.4 and ISO 2553: Same Idea, Different Grammar

Both systems use an arrow, a reference line, and a fillet triangle, but they place information differently. Under AWS A2.4, details below the reference line apply to the arrow side; details above it apply to the other side. ISO 2553 reverses that arrangement.

Fillet size is another trap. ISO 2553 may specify leg length or throat thickness, often marked z or a. On an equal-leg fillet, throat is roughly 70 percent of leg, so a 6 mm leg has about a 4.2 mm throat. AWS practice generally dimensions the leg.

Pitch is the third difference. AWS measures from center to center of adjacent segments. ISO 2553 uses the clear distance between them. A 6 mm pitch on an ISO drawing is therefore a different weld pattern from a 6 mm pitch on an AWS drawing.

The Tail, the WPS, and the Limits of a “Complete” Symbol

The tail is where the symbol points to the paperwork. It can carry a process designation, a specification, or a WPS number. That number is important: it leads the welder to the qualified procedure that controls the actual welding variables.

A symbol with a tail reference can be complete on its own, but only because the tail connects it to the WPS. If the tail is empty, look for a general note or a procedure listed elsewhere. Never treat a bare triangle and two numbers as the whole instruction.

The fillet weld symbol conventions are worth reviewing until they become automatic, especially the arrow-side rule. A symbol placed on the wrong side of the line reverses the weld location, and on a one-sided access joint that error can be expensive.

When the Print Is Ambiguous: Ask Before You Strike an Arc

A print with 2-6 and no standard block is a classic ambiguity. It could mean AWS center-to-center pitch or ISO clear-gap pitch. The professional move is an RFI, or request for information, before fabrication. State the drawing number, the detail, and your question. When the answer arrives, keep it with the shop copy and make sure the drawing is updated.

Documentation matters because memory fades and crews change. A verbal answer that never reaches the drawing becomes someone’s guess. If the RFI changes the weld, the revision should travel with the work.

Drawing Notes and Shop Standards: Read the Fine Print

General notes can prohibit intermittent welds entirely, require seal welds, or name the governing standard. Shop standards can fill in house preferences, but they do not override the project code or a qualified WPS. Check the contract’s order of precedence when documents conflict.

Assumptions are the quietest failure mode. A welder moving from a steel shop under AWS D1.1 to an aluminum job under D1.2 can carry over the wrong habits. Aluminum reacts differently to heat, cleaning, and fit-up. Our aluminum MIG welding guide explains those variables, but the project WPS still has the final word.

A Short Code Checklist for the Shop

• Which symbol standard governs: AWS A2.4 or ISO 2553?
• Does the project code permit intermittent welds here?
• Is the WPS number in the tail, or is there a general note?
• Does a drawing note change length, pitch, or pattern?
• Has every RFI answer been documented and added to the shop copy?

The symbol is a contract, but it is not the whole contract. Read the tail, find the WPS, confirm the governing standard, and ask before you guess. That habit prevents more bad welds than any measuring trick.

Real-World Examples, Common Mistakes, and a Practical Checklist

Symbols only cause trouble when they meet steel. The rules from earlier sections are clean on paper; the shop floor is where pitch drifts, arrow sides get flipped, and someone decides a few extra inches of weld can’t hurt. The four scenarios below are the ones that come up again and again, and each one shows why the number on the print matters more than the instinct of the hand holding the stinger.

Example 1: A Trailer Frame Crossmember at 2-6

A crossmember welded to the main rail with a 2-6 callout is a classic fatigue detail. The drawing asks for 2 in. of weld on 6 in. centers, and the welder has to make two decisions the symbol does not spell out: where the first segment starts, and where the last one lands.

Both ends of the joint deserve attention. A weld that stops right at the end of a member creates a stress concentration at the most highly loaded point, which is exactly where fatigue cracks like to begin. On trailer frames, the common practice is to keep segments away from the extreme ends, or to run a short continuous weld where the load path transfers, depending on what the WPS and drawing require. The symbol tells you how much weld and how often; the code and the detail tell you where. That is why the print reading section matters as much as the arithmetic.

Extra weld is not a safety margin here. Adding segments to a fatigue-critical crossmember increases heat input, changes the residual stress pattern, and can pull the rail out of square. A welder who “helps” by welding solid may hand the fabricator a frame that needs straightening before it goes to paint.

Example 2: Stainless Handrail, Crevices, and Rust Bleed

Stainless handrails on a marina or a wash-down area are a textbook case of a stitch weld fighting its environment. Every gap between segments forms a crevice, and crevices are a known corrosion initiation point in wet or marine service. Water sits in the gap, oxygen differentials develop, and chlorides concentrate. The result is usually not a structural failure but something almost worse for the customer: brown bleed lines running down a bright finished surface.

The fix normally comes from the design side, not the torch. Teams move to a continuous weld, a sealant at the open ends, or a full penetration detail with a post-weld passivation step. If an intermittent weld must stay, the ends of each segment need to be properly tied in and cleaned, not left as ragged terminations that trap contamination. For anyone working aluminum or stainless in these environments, prep and cleaning discipline is the same conversation as aluminum cleaner for welding: how to prep aluminum right — the surface condition decides whether the joint survives.

Example 3: Thin-Gauge Enclosure and Oil-Canning

Now flip the problem. On a 16-gauge sheet metal enclosure, a continuous weld around a panel puts so much heat into a small area that the sheet buckles and oil-cans. A stitch weld is the engineer’s tool for exactly this: less heat input, more time for the panel to cool between segments, and a flatter finished surface.

The trade-off is measuring. On thin sheet, a segment that runs long is not just a dimensional error; it is a heat sink that pulls the panel. Short, controlled segments with proper crater fill, spaced on measured centers, keep the distortion predictable. This is also where sequence strategy earns its keep. Backstep and balanced welding across the panel do more for flatness than any amount of clamping after the fact.

Example 4: The Beam Connection That Got Too Much Weld

A welder looks at a beam-to-plate connection called out as intermittent, decides it looks light, and runs it solid. It passes visual inspection and feels like good workmanship. Then the fabricator measures the beam and finds it pulled out of tolerance, and the shop spends a shift with a torch and a come-along fixing a problem that the print never asked for.

This is the most common nonconformance in stitch welding, and it is almost always well-intentioned. Extra weld beyond the specified size or length is a nonconformance, not a bonus. It adds distortion, filler metal, arc time, and inspection burden, and on a connection designed for a specific load path it can change the behavior the engineer intended. If a joint genuinely looks under-welded, the answer is a question to the engineer, not a decision at the bench.

The Mistakes That Cause Most Rework

• Confusing pitch with gap. Pitch is center to center, so 2-6 leaves a 4 in. gap, not a 6 in. one. Reading it as a gap produces too few segments on every joint.
• Measuring from weld edge to weld edge. Measuring pitch from weld edge to weld edge rather than center to center makes every gap short and every segment count wrong. Mark centers and the geometry takes care of itself.
• Reversing the arrow side. Information below the reference line applies to the arrow side under AWS convention. Flip it and you weld the wrong face, which is expensive on a joint with access from one side only.
• Counting tack welds as segments. Tack welds left in place can become part of the finished joint only when the WPS permits it; otherwise they must be removed or fused into the final weld. On fatigue or pressure work, an unfused tack is a crack starter.
• Running short at the ends. The first and last segments are the ones welders rush. They are also the ones inspectors measure.
• Welding over mill scale, paint, or primer. Contamination drives porosity and lack of fusion, and on intermittent welds it also leaves poorly tied-in segment ends.
• Ignoring the WPS. Size, length, and pitch on the print tell you what; the WPS tells you how. A symbol is not a complete instruction without it.
• Guessing at a smudged print. Asking for a legible drawing takes ten minutes. Tearing out a wrong weld takes ten hours.

For a refresher on how the underlying symbol elements are constructed, the Miller welding symbol guide and this breakdown of fillet weld symbols are both worth keeping on the shop computer. If your work involves aluminum structures where intermittent welds and distortion control come up often, the practical process notes in this aluminum MIG welding guide pair well with the symbol rules here.

Pre-Weld, During-Weld, and Post-Weld Checklist

A pre-weld check of size, length, pitch, pattern, and WPS reference catches most stitch weld errors before the arc starts. Everything after that is discipline.

Stage	Checks
Pre-weld	Confirm size, length, pitch, and pattern against the print; verify arrow side; read the WPS and confirm the process; check fit-up and joint gap; remove mill scale, oil, and paint from the weld zone; mark segment centers along the joint; confirm tacks are acceptable under the WPS.
During weld	Start on the marked center line and work outward; hold segment length with a tape, not by eye; fill craters and taper out at segment ends; watch the pitch count as you go; check for arc blow and adjust ground or technique; clamp or backstep to manage distortion.
Post-weld	Measure size with a fillet gauge; check segment length and center-to-center pitch with a tape; confirm total segment count and end placement; inspect for craters, undercut, spatter, and incomplete fusion; clean and document; flag any drift from the drawing before the part leaves the station.

Two external references are useful for backing up the reasoning above. The Open Washington welding textbook chapter on weld symbols explains the reference line conventions, and OSHA’s 1910.252 welding regulations cover ventilation and exposure requirements that apply whenever starts and stops change your fume pattern.

The Takeaway

Length first, pitch second, centers not gaps. A stitch weld callout is not a rough guide or a shop preference; it is a designed quantity of weld, and the drawing plus the governing code is the authority. Read the symbol carefully, mark the centers, weld exactly what is called out, and ask before you add or subtract anything. Do that, and 2-6 stops being ambiguous and starts being just another number on a print you know how to build to.

Frequently Asked Questions

What does 2-6 mean on a welding symbol?

It describes an intermittent fillet weld with 2 inch long segments spaced on 6 inch centers. The first number is always the weld length and the second is the pitch, so the unwelded gap between segments is 4 inches. On a metric drawing the same callout would appear in millimeters.

Is stitch welding the same as intermittent welding?

In practice, yes. Stitch weld is shop language for an intermittent weld, and AWS terminology treats it as a nonstandard term. The drawing symbol is the same either way, so always read the length and pitch rather than relying on the word used in a note.

Is pitch measured center to center or between the welds?

Under AWS A2.4, pitch is measured from the center of one weld segment to the center of the next. ISO 2553 defines it as the clear distance between segments instead, so confirm which standard governs the drawing before you mark anything.

Where do length and pitch go on a stitch weld symbol?

Both go to the right of the weld symbol, with the length first, a dash, then the pitch. The weld size goes to the left of the symbol, and the symbol itself sits above or below the reference line depending on which side of the joint is welded.

Can stitch welds be staggered on both sides of a joint?

Yes. A staggered intermittent weld is shown by offsetting the symbols on opposite sides of the reference line so the segments alternate along the joint. The usual convention is to offset by half the pitch, which places each weld centered between the welds on the other side.

What is the difference between a stitch weld and a tack weld?

A stitch weld is a specified finished weld of a defined length and pitch. A tack weld is a temporary locating weld used to hold parts in alignment, and it does not count toward the specified weld unless the procedure allows it to be fused into the final joint.

Do stitch welds reduce distortion?

They usually do, because less weld metal and less arc time mean less heat input into the part. The benefit depends on segment length, pitch, sequence, and part stiffness, and it disappears if the welder adds extra weld or concentrates heat in one area.

What if the drawing shows a length but no pitch?

Then the weld is not intermittent at that location. A single dimension to the right of the symbol gives the length of a weld that is shorter than the joint, and the drawing should locate it with dimension lines or notes. If no length appears at all, the weld runs the full length of the joint.