Sewing and seamsSewingGarment washingInspection

Broken Stitch

Stitches that break in the finished seam, often when the seam is stretched, washed or worn. The seam type, thread strength, stitch density or damage to the thread during sewing is usually the cause.

By Published 4 min read

https://textilenotes.com/quality/defects/broken-stitch

Diagram of a stitch line broken in the middle with loose thread ends.

Likely causes at a glance

  • Method

    • Seam or stitch type not extensible enough for a stretch fabricCheck: Stretch the seam to the fabric's working stretch and see where it cracks
    • Stitch density too low or too highCheck: Count SPI against specification and test seam strength

  • Material

    • Thread too weak for the seam loadCheck: Compare thread size and type with the seam requirement; run a seam strength test
    • Thread damaged by needle heat on synthetic fabricsCheck: Check for fused or glazed thread; test at lower speed

  • Machine

    • Burr or sharp edge on needle eye, hook, looper or thread guideCheck: Run a nylon stocking or thread over the thread path to find snags
    • Tension too highCheck: Reduce tension to the lowest value that gives a balanced stitch

  • Operator

    • Seam stretched or pulled during sewingCheck: Watch handling; check whether breaks are on specific operators' work
On this page
  1. What is a broken stitch?
  2. What it looks like
  3. Where it occurs
  4. Likely causes
  5. Machine-related causes
  6. Material-related causes
  7. Operator and process-related causes
  8. Method-related causes
  9. How to confirm the cause
  10. Immediate containment
  11. Corrective action
  12. Preventive action
  13. Inspection notes
  14. Factory checklist

What is a broken stitch?#

A broken stitch is a stitch that has snapped in a finished seam. Unlike a skipped stitch, the stitch was formed correctly, but the thread later broke: during sewing, pressing, washing, or wear. Broken stitches open the seam, and on chainstitch seams the break can run along the seam.

What it looks like#

  • Short thread ends sticking out of the seam.
  • A seam that looks fine relaxed but cracks when stretched.
  • Seams that open after the first wash or after trying on.
  • Breaks clustered at points of high stress: crotch seams, armholes, waistbands, side seams of fitted knits.

Where it occurs#

  • Stretch knit garments sewn with lockstitch, where the seam cannot stretch as far as the fabric.
  • Stress points such as crotch joins, back rise, underarm and button stands.
  • Heavy fabrics where seams take high loads, such as denim and workwear.
  • Synthetic fabrics sewn at high speed, where the needle heats and damages the thread.

Likely causes#

Stitches break when the load on the thread is higher than the thread can take. The load comes from how much the seam must stretch (seam extensibility), how strong the thread is, how many stitches share the load, and whether the thread was weakened during sewing.

  • Sharp edges in the thread path: a burr on the needle eye, a damaged hook point, a worn looper or a scratched thread guide cuts or frays the thread.
  • Tension too high stretches the thread close to its limit, leaving little strength for wear.
  • Wrong needle size for the thread, so the thread rubs in the needle eye.
  • Thread too fine or too weak for the seam's load or for the fabric's weight.
  • Needle heat damage: at high speed on dense synthetic fabrics, needle temperature can soften or fuse synthetic thread.
  • Low-quality thread with weak places or poor lubrication.
  • Stretching the seam while sewing so the stitches are loaded before the garment is worn.
  • Aggressive handling at later stages: turning garments, pressing, trimming close to the stitches.
  • Wrong stitch type for stretch fabrics. Lockstitch (class 301) has limited extensibility. Knit garments normally use overlock (500 class), coverstitch or flatlock (600 class) or chainstitch (400 class) seams that stretch with the fabric. See stitch types.
  • Stitch density. Too few stitches per inch put more load on each stitch; far too many weaken some fabrics and use up extensibility.
  • Seam construction without reinforcement at stress points.

How to confirm the cause#

  1. Look at the broken ends. Clean, cut ends suggest a sharp edge in the thread path or trimming damage. Frayed ends suggest abrasion or overload. Glazed or fused ends on synthetic thread suggest needle heat.
  2. Stretch test. Extend the seam to the stretch the fabric will see in wear. If the seam cracks before the fabric reaches that stretch, the seam type or tension is wrong for the fabric.
  3. Thread path check. Pull a fine nylon filament or a soft stocking through the thread path and needle eye. It snags on burrs.
  4. Seam strength test. Test seam strength in a laboratory against the requirement. See seam strength.
  5. Compare operators and machines. If breaks come from one machine, check the machine; if from one operator, check handling.

Immediate containment#

  • Hold the affected bundles and garments.
  • Stretch check the same seam on garments sewn since the last good check.
  • Resew or reinforce affected seams where possible.
  • If the breaks are in wash tests, hold shipment of the lot until the cause is found.

Corrective action#

Cause Corrective action
Seam not extensible enough Change to an extensible stitch class; adjust differential feed and tension
Thread too weak Use a stronger thread or a heavier ticket suited to the fabric
Needle heat Reduce speed, use a finer or coated needle, use a thread with heat-resistant properties, consider needle cooling
Sharp edges Polish or replace needle, hook, looper or guide
Tension too high Reduce to the minimum balanced tension
Stitch density Set SPI to specification and verify seam strength

Preventive action#

  • Choose stitch types by fabric stretch at the product development stage.
  • Specify thread size and type for each seam in the operation bulletin.
  • Include seam strength and stretch tests in pre-production testing.
  • Add thread path inspection to preventive maintenance.
  • Replace needles on a schedule, and immediately after any needle strike.

Inspection notes#

  • Stretch seams gently at inline and final inspection, especially on knits.
  • Inspect stress points on every garment in the sample.
  • Broken stitches on structural seams are normally major defects; follow the buyer's manual.

Factory checklist#

  • Stitch class suitable for the fabric's stretch
  • Thread size and type as specified
  • SPI checked against specification
  • Tension at the minimum for a balanced stitch
  • Needle, hook, looper and guides free of burrs
  • Speed suitable for synthetic fabrics and threads
  • Seam stretch test done at inline inspection

Related: skipped stitch, open seam, sewing thread selection.

Was this useful?

Tools for this topic

Related defects

Related technical notes

Quality & DefectsGuide4 min read

Sewing Defects: Types, Causes and Prevention

An overview of the sewing defects that cause most repairs and rejections, grouped by stitch, seam and assembly problems, with the usual causes and where to look first.

Garment ProductionGuide3 min read

Sewing Thread Selection: Fiber, Construction and Ticket Number

How to choose sewing thread for garments: core-spun, spun polyester, filament and textured threads, ticket numbers and sizes, matching thread to fabric, seam and needle, and the thread-related causes of seam failures.

TestingGuide3 min read

Seam Strength and Seam Slippage Testing

Seam strength tests measure the force needed to break a seam; seam slippage tests measure how far yarns pull away from a seam under load. Methods, how seams fail, and how thread, stitch density and seam design affect results.