Manufacturer · Fashion & Home Accessories
Core-spun thread is a sewing thread with a continuous polyester filament core wrapped in staple fibres of cotton or polyester. The core provides strength and stable length, while the wrap gives a matt look, good grip and protection from needle heat. That is why core-spun thread is the standard for jeans, workwear and all kinds of load-bearing seams in industrial sewing.
What core-spun thread is and how it is made
During production a continuous polyester filament is fed into the centre of the spinning machine and short fibres are wrapped around it. The result is a single yarn with a "skeleton" inside and a "sheath" outside. Two or three such yarns are then twisted together into a finished thread. The result differs significantly from the two most common types of sewing thread:
- Spun polyester – spun only from short polyester fibres. It is soft and cheap to produce, but less strong at the same thickness.
- Filament polyester – from continuous filaments, very strong and smooth, but shiny and more slippery in the seam.
- Core-spun – combines the two: the strength of filament and the surface of a staple thread.
Cotton or polyester wrap
The wrap determines how the thread behaves. Polyester/cotton (often labelled PC or poly/cotton) has a natural, matt look and tolerates high ironing temperatures, because cotton does not melt. It is the classic choice for jeans and garments that go through stone or enzyme washing. Polyester/polyester (PP) is more colourfast and resistant to moisture and chemicals, and is preferred for workwear, sportswear and technical textiles.
Advantages of core-spun thread in the factory
The reason factories pay a little more for core-spun is not just strength. In real work it solves several practical problems at once.
- High strength at a smaller thickness. You can choose a finer ticket number without losing seam strength, which gives a cleaner look and less puckering.
- Resistance to needle heat. At very high sewing speeds the needle heats up. The staple wrap protects the core and reduces breakage.
- Consistent loop formation. The thread behaves stably in the mechanism and skipped stitches are rarer.
- Low shrinkage. The polyester core limits length change in washing, so the seam does not pucker.
- Abrasion resistance. Suitable for seams that rub during wear – inside leg, waistband, pockets.
When to choose core-spun thread
Not every product needs it. Ordinary spun polyester from our sewing threads section is perfectly adequate for shirts, dresses, blouses and most lightweight garments. Core-spun justifies its price in the following cases:
| Product | Why core-spun | Recommended wrap |
|---|---|---|
| Jeans and denim | Load-bearing seams, stone washing, visible topstitching | Cotton |
| Workwear, uniforms | Wear, frequent industrial laundering | Polyester |
| Jackets and coats | Dense layers, thick spots | Polyester or cotton |
| Bags, backpacks, canvas | High seam tension | Polyester |
| Garment-dyed items | The thread must take the dye | Cotton (with a test before the series) |
Thickness and needle for core-spun thread
Core-spun is offered in the same ticket numbers as other sewing threads. For construction seams on trousers and jackets, ticket 120 and 100 are most often used for lighter fabrics and ticket 80–75 for denser ones. Ticket 50, 40 and heavier are used for visible decorative stitching. The needle must match the thickness: approximately Nm 80–90 for ticket 120, Nm 90–100 for ticket 80 and Nm 100–120 for ticket 40. If the needle is too fine, the thread rubs in its eye and the wrap frays.
Needle and bobbin thread
Both threads do not have to be core-spun. A common practice is to use core-spun in the needle and a finer spun polyester in the same colour in the bobbin. This saves cost, but seam strength is determined mainly by the weaker of the two threads, so for heavily loaded seams it is safer to use core-spun underneath as well.
How to recognise core-spun thread
On the cone label look for designations such as "core spun", "corespun", PC, PP or "poly/cotton". If there is no label, cut a piece of thread and untwist its end: you will see smooth, shiny continuous filaments in the middle and fluffy short fibres around them. When pulled, core-spun thread stretches slightly and breaks sharply, while spun polyester breaks more easily with a frayed end.
Common mistakes
- Choosing too thick a core-spun "just in case" – the seam becomes coarse and puckers thin fabrics.
- A polyester wrap on jeans that will be stone washed – the thread colour and the denim "wear" differently.
- Changing supplier in the middle of a series without testing – strength and thread glide differ between manufacturers.
- Incorrect tension setting – core-spun is stronger but does not forgive excessive tension, which puckers the fabric.
For natural products where an all-cotton composition matters, see also our cotton threads, and for the full range the threads category.
Core-spun and sewing threads from Polkom
Polkom is a Bulgarian manufacturer and supplier of garment accessories with over 30 years of experience. We supply sewing threads, including polyester-core threads, wholesale to garment factories and brands throughout the EU. Send us the fabric, seam type and machines you use, and we will propose the right thickness and colour as well as a sample for testing. The price depends on the wrap type, thickness, put-up and quantity – write to us via our contact page to request a quote.
