Manufacturer · Fashion & Home Accessories
Why does the thread break? The most common causes are incorrect threading, upper tension that is too high, an unsuitable or blunt needle, and thread that is too thick for the needle or has aged. In most cases the problem is solved in minutes: rethread, change the needle and reduce the tension. If the thread keeps breaking, check its quality and its path through the machine for burrs.
Why the thread breaks – check these five things first
- Threading – raise the presser foot (this opens the tension discs) and rethread the whole path from the spool to the needle.
- Needle – fit a new needle of the right size and point, pushed all the way up and with the flat side facing the correct way.
- Upper tension – reduce it by one or two settings and sew a test.
- Thread versus needle – check that the thread number matches the needle size.
- Spool or cone – the thread must unwind freely, without catching in the notch of the spool or on the stand.
Needle-related causes
Blunt or bent needle
A worn point pierces the fabric with effort, and a bent needle hits the needle plate or the hook. Both create burrs that cut the thread. The needle is a consumable – change it regularly, not only when there is already a problem.
Needle too small for the thread
The thread must lie in the long groove of the needle. If it is thicker, it rubs against the fabric with every penetration, heats up and frays. See the table in our article on choosing thread and needle for the fabric.
Unsuitable point
Leather needs a needle with a cutting point, jersey a ball point and denim a reinforced needle. The wrong point leads to skipped stitches and breakage, especially on multi-layer seams.
Tension and threading causes
- Threading with the foot lowered – the thread does not go between the tension discs and the machine forms a "bird's nest" of thread under the fabric, then breaks it.
- A missed thread guide – the thread travels at an angle and rubs against edges.
- Upper tension too strong – especially with thin threads and stretch fabrics.
- Incorrectly inserted bobbin – the bobbin thread unwinds in the wrong direction or the bobbin is wound unevenly.
- Lint between the tension discs – the tension becomes uneven and the thread breaks intermittently.
Thread-related causes
Low-quality thread
Thread of uneven thickness has thin sections that break under load and thick slubs that get stuck in the eye of the needle. Cheap spun threads also shed more lint, which clogs the machine. If the thread keeps breaking after changing the needle and tension, replace it with a proven sewing thread.
Old or dried-out thread
Thread stored for years in a bright, dry place loses strength – especially cotton and viscose. Do a quick test: pull 30 cm between your hands. If it breaks easily with a "snap", the thread should be thrown away. Read more about proper thread storage.
Unsuitable thread type
- cotton thread on jersey – it cannot withstand the stretching;
- viscose embroidery thread in a construction seam;
- thread that is too thin for dense fabric or a multi-layer seam;
- filament thread on a cross-wound spool placed on a horizontal pin – it slips and tangles.
Heat at high speed
On industrial machines, the needle heats up from friction with the fabric. Ordinary synthetic thread can soften and break. The solutions are core-spun thread, needles with a special coating, thread with a suitable lubricant or a lower speed on heavy operations.
Machine-related causes
- scratches or burrs on the needle plate, hook or presser foot – often after the needle has struck them;
- incorrect hook timing after an impact or jam;
- lint build-up in the hook area;
- dry moving parts without lubrication.
If, after all these checks, the thread keeps breaking at the same point in the cycle, call a technician. Timing and polishing the hook are not operator tasks.
Is the needle thread or the bobbin thread breaking?
| Symptom | Probable cause |
|---|---|
| Needle thread breaks close to the needle | needle, tension, burr in the eye |
| Needle thread breaks high up | spool, stand, thread guides |
| Bobbin thread breaks | bobbin, bobbin case, bobbin tension |
| Bird's nest of thread under the fabric | threading with the foot lowered |
| Breaks only on thick sections | needle or thread too thin |
Prevention in the garment factory
- a schedule for changing needles based on working hours;
- daily cleaning of lint from the hook and loopers;
- a standardised thread–needle list for each fabric in the tech pack;
- proper storage of cones – closed, in the shade, away from heating;
- a test seam with every new batch of fabric or thread.
Differences between machine types
Domestic sewing machines
On domestic machines, the most common causes are threading and the bobbin. Use bobbins designed for the specific model – other bobbins with a slightly different height create uneven bobbin tension. Place the spool so that the thread unwinds without catching in the notch.
Industrial machines
On industrial machines, speed and heat matter as well as the needle and tension. On heavy operations reduce the speed, check the thread guides for wear and make sure the cone stands steadily on the stand and the guide above it is exactly in line.
Overlock and coverstitch
There the problem is often the threading order: on most machines the loopers are threaded first, then the needles. If the needle thread breaks, check that it has not passed on the wrong side of a thread guide.
Reliable thread from Polkom
Polkom is a Bulgarian manufacturer and wholesaler of garment accessories with over 30 years of experience. In our threads category you will find sewing, cotton and technical threads in many colours. If your thread keeps breaking despite correct settings, send us details of your fabric, machine and needle via our contact page – we will suggest a suitable thread and a sample for testing.
