Thread is one of those specs that gets skipped in a lot of tech packs — and then causes problems at production. The right thread for jersey overlock seams is corespun polyester at Tex 27 (also called Ticket 120). It's strong enough to hold under stress, elastic enough to move with the fabric, and resistant to the heat and chemicals involved in dyeing and finishing.
Specifying "polyester thread" without a Tex number leaves the factory to decide — and they'll use whatever is loaded on the machine. That might be the right choice. It might not. A Tex number takes 5 seconds to add to your BOM and removes all ambiguity.
Tex 27 for overlock seams. Tex 18 for coverseam hems. These are two different specs — both need to appear in your BOM if you're using both seam types.
Understanding thread sizing: Tex vs Ticket
Thread weight is expressed in two systems that often appear together. Tex is the direct system: the weight in grams of 1,000 meters of thread. Higher Tex = heavier thread. Ticket (or Nm) is an indirect system: higher ticket number = finer thread. They're inversely related.
Production specs for your tech pack BOM
| Spec | Value | Notes |
|---|---|---|
| Thread type | Corespun polyester | ISO 180/2 construction |
| Tex size | Tex 27 | Also listed as Ticket 120 |
| Color | Match to fabric | Specify Pantone reference or "self color" |
| Application | Overlock seams | Side, shoulder, sleeve seams |
| Properties | High tenacity, colorfast | Resistant to chemicals and abrasion |
In FlatLabs PRO, thread specs are automatically split in your BOM — Tex 27 for overlock seams, Tex 18 for coverseam hems — based on the seam types in your construction spec.
Why corespun polyester specifically
Corespun thread has a polyester filament core wrapped with a cotton or polyester staple fiber. The core provides tensile strength — it won't break under the stress of overlock sewing at high speed. The outer wrap provides the surface properties: how it runs through the needle, how it feels, how it takes dye.
For jersey, corespun polyester is the correct choice — not spun cotton, not textured polyester. Cotton thread has lower tenacity and can break under the stretch loads of a knit seam. Textured (bulked) polyester is too thick for standard overlock applications. Corespun hits the right balance of strength, elasticity, and runnability.