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I once spent forty minutes convinced my machine was possessed, only to find the thread wrapped backward around the spool pin. Classic rookie move, and one I still see on repair benches every week.
When your thread keeps breaking on sewing machine projects, the culprit hides in one of five usual suspects: tension, needles, threading path, bobbin setup, or sheer speed. Nine times out of ten, it’s not the machine’s fault, it’s a small detail begging for attention.
Grab your seam ripper and a cup of patience, because we’re about to hunt down exactly what’s snapping your thread and fix it for good.
Table Of Contents
Key Takeaways
- Most thread breaks trace back to five root causes: tension settings, needle condition, threading path, bobbin setup, or sewing speed, rather than a faulty machine.
- Rethreading incorrectly (skipping guides, sewing with the presser foot down, or misaligning the take-up lever) is one of the most common and overlooked causes of snapped thread.
- Keeping tension between 3–5, matching needle size and type to your fabric and thread, and replacing dull or bent needles solves the majority of persistent breakage issues.
- Regularly cleaning lint from the bobbin case, inspecting the throat plate and hook area for burrs, and storing thread properly all prevent hidden mechanical wear that leads to repeated thread snapping.
Why Sewing Machine Thread Breaks
Thread breaking mid-project is frustrating, but it’s rarely a mystery once you know where to look. Most causes fall into a handful of usual suspects, from tension settings to needle problems to plain old thread quality.
If you want to work through those tension, needle, and threading checks step by step, this guide to simple sewing machine repairs walks you through fixing the most common culprits.
Let’s walk through what’s actually going on, starting with the fastest way to narrow down your culprit.
Quick Cause Checklist
Ever chase a thread break for twenty minutes only to find it’s something dumb? Here’s your rapid diagnostic shortcut: check thread tension, rethreading path, needle type, bobbin condition, and lint buildup, in that order.
This quick machine check catches most thread breakage causes fast. Nail down which trigger you’re dealing with before touching a single screw. Using an analysis checklist can help make sure you find the true cause rather than just treating surface-level symptoms.
Upper Thread Vs Bobbin Thread
Two threads, two jobs. The upper thread runs from spool to needle, showing up on your fabric’s top; the bobbin thread hides underneath, finer and lighter so it doesn’t add bulk.
They interlock mid-fabric when tension’s right. Mismatch weight or fiber content, though, and you’ll see:
- Top thread breaking
- Bobbin thread breaking
- Loose stitches
- Fabric puckering
- Visible thread nests
Breaks After Few Stitches
Snapping right after you start? Nine times out of ten, it’s needle trouble, dull needle impacts, improper installation, or incorrect sizing all create friction points that shred thread fast.
| Symptom | Likely Cause |
|---|---|
| Breaks in first 3-4 stitches | Bent or dull needle |
| Random mid-seam snaps | Damaged needle eye |
| Snags every few inches | Wrong needle-fabric match |
Check needle sharpness before blaming tension.
Breaks on Thick Seams
Bulky cross seams hit the needle with sudden fabric resistance, and that’s where thread snaps mid-stitch.
Try this:
- Reduce seam bulk by pressing seams flat first
- Bump needle size up for heavy layers
- Loosen top thread tension slightly
Watch for needle heat buildup too, friction on thick layers heats the needle, which weakens thread fast.
Breaks at High Speed
What happens when you floor the pedal on a straight seam? Heat builds fast, and thread friction heat starts weakening fibers mid-stitch. High-speed tension spikes and motor heat effects team up against you.
Solution: Ease off pace on long runs, let tension settle, and give the machine breathing room. Rapid stitching stress adds up—slow down before thread breakage becomes your new normal.
Rethread The Machine Correctly
Half the thread breaks I fix come down to one thing: bad threading. It sounds too simple, but skipping a guide or missing the take-up lever throws everything off. Here’s how to get it right, step by step.
Raise The Presser Foot
2.1 Raise The Presser Foot
Here’s a mistake I see constantly: threading with the foot down. That leaves your tension discs open, so thread never seats right, causing skipped stitches or snapped upper thread later.
Always lift the foot first. This:
- Opens the tension discs properly
- Clears space around the needle area
- Prevents fabric snagging
- Makes rethreading smooth, not frustrating
Follow Every Thread Guide
2.2 Follow Every Thread Guide
Skipping a guide is like skipping a step on a ladder, you might make it, but you’re asking for trouble. Each guide keeps tension disk seating correct and helps with proper loop cycling.
Trace your machine’s diagram slowly. An incorrect threading path is the top cause of machine threading errors, so when you rethread the top thread, go guide by guide, don’t rush it.
Check The Take-up Lever
2.3 Check The Take-up Lever
That little arm swinging above your needle is the unsung hero of every stitch. Vertical alignment matters, misaligned lever positioning causes upper thread breaking and jams. Check lever clearance, watch for binding through its full cycle. Nicks invite thread abrasion. Wear at pivot points disrupts timing, so lubricate the shaft regularly during routine sewing machine troubleshooting.
While you’re at it, keeping thread spools tidy with color-coded silicone bobbin clips for thread organization can prevent the tangles that strain your take-up lever in the first place.
Prevent Spool Notch Catching
2.4 Prevent Spool Notch Catching
That tiny notch on your spool rim seems harmless, until it snags your thread mid-stitch. Spool pin placement matters: horizontal pins need thread feeding back-to-front, vertical pins from the right. Rotate the spool if the notch faces wrong. A spool cap smooths the thread path and stops snagging cold—cheap insurance against breakage.
Test on Scrap Fabric
2.5 Test on Scrap Fabric
Never trust a rethread until it proves itself on a test seam. Grab scrap matching your project’s fabric compatibility, thickness included, and sew a few inches.
Watch stitch formation closely for puckering or loose loops. Change one variable at a time, isolating variables like tension or needle size, and jot down results. This habit turns guesswork into real sewing troubleshooting, catching breakage patterns before they ruin your actual project.
Fix Thread Tension Problems
If rethreading didn’t fix things, tension is probably your culprit. It’s the setting most people fear touching, but it’s not as scary as it looks once you know what to check. Here’s how to track down the problem and set things right.
Start Between Tension 3–5
Tension 3–5 is your home base for most sewing machine troubleshooting. Start at 4, then nudge by 0.5 increments based on fabric weight — knits do better near 3 to avoid curling, wovens prefer 4–5 for even feeding. Always test stitch uniformity on scrap fabric first. Balancing top thread tension against the bobbin is what actually stops thread breakage before it starts.
Loosen Tight Upper Tension
Sound familiar? That upper thread snapping mid-seam usually means your tension is too tight for the job. Drop it in small steps and re-test:
- Fabric feed resistance from rough plates
- Material weight impact on delicate fabrics
- Sewing speed effects amplifying imbalance
- Thread path deviations at guides
- Needle eye friction with thick thread
Ease the tension disk adjustment down half a unit at a time until stitches feed smoothly again.
Check Bobbin Case Tension
Loosened the top and still snapping? Grab the bobbin case, hold it by the thread, and let it drop. It should fall an inch or two, bouncing slightly.
No movement means it’s too tight. Free-falling means loose. Adjust the tiny screw in quarter turns, and check spring seating so it isn’t bent or bird-nesting your stitches.
Balance Top and Bobbin Threads
Once both tensions read right, prove it. Grab two contrasting thread colors and stitch a scrap seam.
If bobbin color peeks through the top, nudge upper tension up a quarter turn. Top color showing underneath? Loosen it slightly.
You’re after neutral pull verification — even stitch symmetry, no ridges, no loops, on both sides.
Avoid Tension Spikes
Every so often thread breaks not from bad tension itself, but from sudden changes in it mid-seam.
Consistent feed pressure keeps things stable, so avoid fabric pulling and slow down for thick seam navigation.
- Ease into speed changes
- Keep hands guiding, not dragging
- Let feed dogs do the work
Smooth thread flow depends on steady habits, not quick fixes.
Choose The Right Needle
Sometimes tension isn’t the villain at all, it’s the needle. A worn or mismatched needle can wreck your stitches no matter how perfect your threading is. Here’s what to check before you blame anything else.
Replace Dull or Bent Needles
A dull or bent needle is often the real culprit behind skipped stitches and thread snags. Needle friction increases, fabric gets stressed, and breaks follow.
Solution: run a fingernail over the tip, feeling for burrs, then replace the needle. Fresh needles restore stitch consistency instantly, no guesswork, no more mystery needle problems.
Match Needle to Fabric
Grab your fabric and ask: is it silk, cotton, or denim? That answer decides your needle gauge.
Fine 60/8-70/10 needles suit silk and chiffon. Cotton poplin likes universal 70/11-90/12. Denim demands 90/14-100/16.
Match point type to weave: ballpoint for knits, sharp universal for wovens, wedge for denim.
Solution: test scraps first—wrong sizing causes puckering and skipped stitches.
Match Needle to Thread
Ever thread a needle and feel it fighting you the whole way? That’s usually a thread weight mismatch, not bad luck.
Match eye size to thread diameter: 40 weight likes 80/12, decorative 30 weight needs 90/14-100/16. Metallic or textured threads want larger, elongated eyes for friction reduction.
Wrong needle for the thread means fraying and skipped stitches—so replace the needle before blaming your machine.
Install Flat Side Back
Here’s the part nobody warns you about: pop that needle in backward, and you’ve built a breakage machine before you’ve even sewn a stitch.
Install a needle backward, and you’ve built a breakage machine before you’ve even sewn a stitch
Flat side back installation needs the needle pushed fully into the clamp, flat facing the machine’s rear. This component alignment precision keeps the hook timing correct.
Skip it, and thread breakage prevention goes out the window—your sewing machine thread keeps breaking no matter how perfect your tension adjustment is.
Inspect Needle Eye Damage
That tiny hole can wreck your whole seam. Grab a magnifier and check the eye for burrs or rounded edges catching your thread. A misaligned eye looks off-center against light, and corrosion causes staining or snagging. Fine fabrics show fraying fast.
A bent or dull needle with eye damage is a leading cause of hidden sewing machine problems—swap it before real thread breakage prevention fails you.
Check Bobbins and Thread Quality
Sometimes the needle and tension are fine, and the real troublemaker is hiding down in the bobbin. A wrong-size bobbin, bad wind, or old thread can undo all your other fixes without you even knowing it. Here’s what to check down below before you blame anything else.
Use Correct Bobbin Size
5.1. Use Correct Bobbin Size
That rattling, uneven stitch might just be a size mismatch. Class 15, L style, and M style bobbins aren’t interchangeable—measure diameter and height before buying.
- Bent case latches
- Skipped stitches
- Snapped thread
- Jammed hooks
- Wasted fabric
Check rotation direction and stick with OEM over generic knockoffs. Color coding helps confirm compatibility fast.
Avoid Overfilled Bobbins
5.2. Avoid Overfilled Bobbins
Getting the size right won’t help if you’ve packed that bobbin too full. Stop winding at the outer edge, not beyond it, to prevent bulging edges that create bobbin rotation friction. An improperly wound bobbin fights the case instead of spinning smooth. Use your automatic winder settings if your machine has them, and leave a hair of clearance—prewound bobbins get this balance right every time.
Insert Bobbin Correctly
5.3. Insert Bobbin Correctly
Winding it right means nothing if you drop it in backward. Thread path alignment matters—thread should unwind so the bobbin spins clockwise into the case, not against it.
Check bobbin seating stability before closing the cover:
- Presser foot up
- Bobbin drops in flat
- Thread follows the notch
- Pull tail—it feeds free
- Cover clicks shut
Avoid Old Brittle Thread
5.4. Avoid Old Brittle Thread
That bobbin sitting flat means nothing if the thread itself is shot. Run it through your fingers—rough or stiff feel means it’s done. Check for cracking along the fiber, faded color, or dull patches.
Old thread snaps mid-seam, jams needles, and leaves lint everywhere. Test on scrap first. When in doubt, toss it—cheap insurance against a ruined project.
Store Thread Properly
5.5. Store Thread Properly
Funny how thread damage often starts on the shelf, not the machine. Keep spools cool, dry, and shaded—UV damage prevention matters more than folks think.
Ideal humidity levels sit around 40-60%. Cooler temps preserve thread strength and durability, slowing fiber degradation before it ever hits your needle.
- Use clear, labeled bins
- Keep away from windows
- Separate by thread weight
Clean and Inspect Machine Parts
Sometimes the problem isn’t your thread or your needle at all, it’s the machine itself. Dust, lint, and tiny scratches build up in places you can’t see, quietly wrecking your stitches. Here’s what to check, part by part.
Clean Bobbin Case Lint
Lint buildup under the bobbin case is sneakier than it looks, and it’s often the real reason your thread keeps snapping.
A soft brush or narrow vacuum nozzle clears the bobbin area and tension springs safely. Skip canned air, since moisture can cause rust.
Check hotspots weekly: hook area, take-up lever base, and bobbin notch. Note the case orientation before removing it.
Check Throat Plate Burrs
Grab a flashlight and check your throat plate for tiny burrs, those raised edges form where the needle strikes repeatedly.
- Detecting micro-nicks near the needle hole
- Evaluating plate flatness with a straight edge
- Polishing plate surfaces with crocus cloth
- Inspecting needle holes for rough edges
Needle strike causes worsen with misalignment, chewing up stitch quality fast. This is basic sewing machine maintenance you can’t skip.
Inspect Hook Area Scratches
That shiny hook zipping around your bobbin case can wreck your thread if it’s scratched. Run a fingernail over the surface, deep gouges near the throat or nose mean reduced load capacity and thread-shredding trouble. Light, uniform scratches? Usually fine.
But if you spot bare metal or coating damage, that’s a corrosion risk worth flagging before your next project.
Remove Adhesive Buildup
Ever notice a gummy patch near the needle plate after using fusible interfacing? That’s adhesive residue, and it grabs thread like flypaper.
Test a small area first, then try a hair dryer to soften it, wiping with a plastic scraper. Isopropyl alcohol or vegetable oil works too. Stubborn spots respond to a baking soda paste—rinse and dry thoroughly afterward.
Stop Pulling The Fabric
That toothed mechanism under the presser foot is built to pull fabric through evenly, no help needed. Tugging fights the machine’s own feed dog mechanics, bending the needle and snapping thread instantly.
- Keep hands near the foot, guiding only
- Let stabilizers support stretchy fabric
- Watch for puckering (over-tight tension)
- Preserve fabric grain alignment
- Stop and adjust if fabric feels stuck
Top 6 Helpful Sewing Items
Fixing thread breaks is one thing, but having the right gear on hand makes it a lot less likely to happen again. Some tools just make your sewing life easier, cutting down on guesswork and frustration. Here are six items worth keeping in your sewing kit.
1. Schmetz Universal Sewing Machine Needles
Fifty needles, five cards, one job: fixing that mystery thread break. Schmetz’s 130/705 H system fits Singer, Brother, and Bernina alike, with a slightly rounded point that works through wovens and knits without complaint.
I keep these on my bench for exactly this reason. When a customer swears they’ve tried everything, a fresh universal 80/12 often solves it in one swap, no fancy diagnostics required.
| Best For | Home sewists and small-shop owners who want a reliable, all-purpose needle for everyday machine repairs and general sewing on woven or knit fabrics. |
|---|---|
| Material | Metal |
| Quantity | 50 needles |
| Compatible Machine Type | Household |
| Primary Function | Needle Replacement |
| Brand Compatibility | Singer, Brother, Bernina |
| Use Case Scope | General Sewing |
| Additional Features |
|
- Fits a wide range of household machines, including Singer, Brother, and Bernina
- Handles both woven and knit fabrics with consistent stitch quality
- Comes in a generous 50-needle pack, so you’re stocked up for a while
- Not designed for industrial sewing machines
- May not be ideal for delicate or highly specialized fabrics
- Universal design means it’s a jack-of-all-trades rather than a specialist for tricky materials
2. Organ home sewing machine needles assortment
Organ needles bring size range to the table where Schmetz gave you variety of point styles. This assortment spans sizes 9 to 18, so you’re covered from silky voile to stubborn denim without a single trip back to the store.
The chrome plating resists corrosion, and individually wrapped envelopes keep each size sharp and separated. If you sew a wide mix of fabrics, this is your backup insurance drawer for those "wait, I need an 18" moments.
| Best For | home sewers who work with a variety of fabric weights and want a ready-to-go stock of common needle sizes for their 15×1 sewing machine. |
|---|---|
| Material | Metal |
| Quantity | 50 pieces |
| Compatible Machine Type | Household (15×1) |
| Primary Function | Needle Replacement |
| Brand Compatibility | 15×1 Machines |
| Use Case Scope | General Sewing |
| Additional Features |
|
- Covers five essential sizes (9, 11, 14, 16, and 18), so you’re set for everything from lightweight voile to heavy denim
- Individually wrapped envelopes keep needles sharp and organized by size
- Chrome plating helps resist corrosion for longer-lasting use
- Only compatible with 15×1 flat shank machines, so it won’t work for other machine types
- Limited to just the five included sizes, with no room for specialty needles
- Not ideal for sewists who need a wider variety of point styles rather than just sizes
3. Doublelin APW-60S2 Prewound Bobbins Size A White
Needles get all the glory, but bobbins cause just as many headaches. These Size A prewound bobbins fit Class 15/SA156 cases and skip the winding hassle entirely.
The 60S/2 polyester center minimizes puckering on delicate fabrics like batiste or silk. Plastic sides feed smoothly and cut down on lint buildup.
At 144 per box, you won’t run out mid-monogram. Just don’t try forcing them into a Size L slot.
| Best For | Machine embroiderers and monogrammers working with lightweight fabrics like silk, batiste, and cotton lawn who want smooth feeding and minimal puckering without winding their own bobbins. |
|---|---|
| Material | Polyester/Plastic |
| Quantity | 144 bobbins |
| Compatible Machine Type | Embroidery Machines |
| Primary Function | Bobbin Thread |
| Brand Compatibility | Class 15, SA156 |
| Use Case Scope | Fine Embroidery |
| Additional Features |
|
- 144 prewound bobbins mean less downtime rewinding thread mid-project
- Low-stretch 60S/2 polyester core keeps delicate fabrics from puckering when the hoop comes off
- Compatible with Class 15, SA156, and Size A bobbin cases, including machines with thread-remaining sensors
- Not designed for quilting, free-motion quilting, or general apparel construction
- Size A bobbins won’t fit Size L or Size M slots, so machine compatibility must be checked first
- Too lightweight (60S/2) for heavier sewing tasks that call for 40S/2 thread instead
4. Assorted Color Bobbin Thread Clips
Once your bobbins are sorted, keeping them matched to the right spool is the next battle. These clips pair bobbins with spools using color coding, so you’re not guessing which blue is which mid-project.
The 20-piece set covers blue, purple, and pink, snapping onto standard spools without tools. One catch: the storage tin sells separately, so grab a small container to keep them corralled and off your workbench floor.
| Best For | Sewists juggling multiple thread colors who want a fast, foolproof way to keep bobbins matched to their spools. |
|---|---|
| Material | Assorted Plastic |
| Quantity | 20 pieces |
| Compatible Machine Type | Standard Sewing |
| Primary Function | Thread Organization |
| Brand Compatibility | Standard Spools |
| Use Case Scope | Thread Organizing |
| Additional Features |
|
- Squeeze-to-slide design makes clipping bobbins to spools quick and tool-free
- Color-coded set helps you spot the right bobbin at a glance, cutting down mid-project guesswork
- Fits most standard spools and Type A, A/15, and L bobbins, so it works with gear you likely already own
- Storage tin isn’t included, so you’ll need to buy a separate container to keep clips organized
- Color options are limited to blue, purple, and pink, which may not cover every thread shade you use
- With only 20 clips per set, larger stashes of bobbins may require buying more than one pack
5. Silicone bobbin holders for thread spools
Ever unwind a spool only to have loose thread snake off and tangle in your bag? These flexible silicone holders wrap around spool tops, gripping with a gentle, non-slip fit that stops unraveling cold.
They stretch to fit openings between 6mm and 13mm, so one holder works for most spools you own. The color-coded pack (60 pieces, four colors) makes matching bobbins to spools quick work, and the silicone won’t fray or damage your thread over time.
| Best For | These bobbin holders are best for sewists, quilters, and embroiderers who want a tidy, tangle-free workspace and an easy way to keep bobbins matched to their spools. |
|---|---|
| Material | Silicone |
| Quantity | 60 pieces |
| Compatible Machine Type | Embroidery/Quilting |
| Primary Function | Thread Organization |
| Brand Compatibility | Universal Spools |
| Use Case Scope | Multi-Craft Use |
| Additional Features |
|
- Flexible silicone design fits a variety of thread spool diameters securely
- Color-coded system with four colors makes organizing and matching bobbins fast and simple
- Smooth, non-slip surface protects thread from damage while preventing unraveling
- Manual measurements mean slight size variations are possible between pieces
- Colors may look slightly different in person than they appear on a screen
- Only compatible with Type A, L, and M bobbins, so it may not suit every setup
6. Sewing Machine Thread Tension Springs
Watch for a stitch that suddenly tightens up, breaks, or nests, since a worn-out spring is often the hidden culprit. These coil or beehive-style springs sit in your tension assembly and add pressure as thread moves through the discs. Once they lose their spring-back, tension gets inconsistent no matter how you adjust the dial.
Replacing one is cheap and simple, and it often fixes problems you’d swear were needle or thread issues instead.
| Best For | Repair techs and sewing machine owners who use Brother, JUKI, or Singer industrial machines (Class 96, 195K, or 20U) and need a reliable fix for inconsistent tension, breaking thread, or nesting stitches. |
|---|---|
| Material | Metal |
| Quantity | 10 pieces |
| Compatible Machine Type | Industrial |
| Primary Function | Tension Part Replacement |
| Brand Compatibility | Brother, JUKI, Singer |
| Use Case Scope | Industrial Repair |
| Additional Features |
|
- Durable metal build that holds up over time
- Lightweight design makes installation and handling easy
- Straightforward replacement process, even for smaller repairs
- Only fits specific industrial models, so it won’t work as a universal part
- Requires careful measurement before installing to ensure proper fit
- Not intended for household or non-industrial sewing machines
Frequently Asked Questions (FAQs)
What happens if bobbin tension is too high?
Funny how tightening things is supposed to help, yet cranking bobbin tension too tight backfires completely. It causes puckered seams, loose top loops, needle strain, and messy bird’s nesting underneath—turning a simple fix into a bigger headache fast.
How to stop thread from snapping?
Rethread from scratch, keep tension around 3–5, and swap in a fresh needle matching your fabric. Clean lint from the bobbin case, then test on scrap fabric first—snapping usually stops once these basics line up correctly.
Why does my string keep breaking when I’m sewing?
Nine times out of ten, it’s bad threading or a dull needle. Old thread, tight tension, or the wrong needle for your fabric all pile stress on that string until it snaps.
What tension should my sewing machine be on?
Somewhere between "loose enough to floss a whale" and "tight enough to snap a guitar string" sits your sweet spot: tension 3–5 for most fabrics, adjusting up for heavy denim, down for delicate silks.
Why does my sewing machine thread keep breaking?
Usually it’s tension too tight, lint clogging the bobbin area, bad threading through the guides, a burred or bent needle, or mismatched thread weights fighting each other. Any one throws off the balance and snaps your thread mid-stitch.
What should I do if my thread keeps breaking?
Start with the basics: raise the presser foot, rethread from scratch following every guide, and check your needle for burrs.
Then test tension on scrap fabric before sewing your actual project—it saves headaches later.
What can cause a sewing machine to break?
The gentlest machines cause the biggest headaches. A sewing machine "breaks" thread through tension mismatches, dull needles, wrong needle-fabric pairing, lint buildup in the bobbin case, burrs on the throat plate, or thread that’s simply too old and brittle to survive the needle’s punishment.
What does it mean if a thread keeps breaking?
Repeated breaks point to a root mechanical issue, not bad luck. Your machine’s telling you something’s mismatched: needle, thread, tension, or threading path. Ignore it, and you’ll keep patching symptoms instead of the actual cause underneath.
How do you fix a thread break on a sewing machine?
Like Theseus following his thread through the labyrinth, you need a clear path back to basics: rethread properly, balance tension between 3–5, swap dull needles, check bobbin quality, and clean lint from tension discs regularly.
Why does my bobbin thread keep breaking?
Nine times out of ten, it’s the upper thread pulling too tight, dragging the bobbin thread through with it. Add a nicked bobbin case or old, brittle thread, and snapping becomes almost guaranteed.
Conclusion
Picture that snapped thread as a frayed rope, not a broken machine. Every fix you just learned, from tension dials to needle swaps, pulls that rope taut again. When thread keeps breaking on sewing machine sessions, it’s rarely bad luck; it’s one small detail asking for attention. Slow down, check your path, and trust your hands. Master these basics once, and smooth seams stop feeling like luck. They become your new normal.
- https://www.superiorthreads.com/education/troubleshooting-broken-thread
- https://www.maggieframes.com/blogs/embroidery-blogs/how-to-fix-bobbin-thread-breaking-comprehensive-troubleshooting-guide
- https://www.singermachines.co.uk/faq/upper-thread-snaping-on-sewing-machine.html
- https://www.thesewingdirectory.co.uk/thread-tension
- http://www.melco-service.com/source1/Troubleshooting_Bobbin_Thread.htm
