Tex 18 is the finer, softer counterpart to the Tex 27 overlock thread. Where Tex 27 is built for strength at the seams, Tex 18 is built for finish quality at the hems. The lower Tex number means less mass per meter — a finer thread that creates a flatter, less visible stitch line on the outside of the garment and a softer profile against the skin on the inside.
It's used in coverseam machines for hemming the bottom of the garment, finishing sleeve openings, and topstitching the neckband. Anywhere the thread will be visible or felt by the wearer, Tex 18 is the right choice.
Always spec two thread weights in your BOM for a jersey t-shirt: Tex 27 for overlock seams, Tex 18 for coverseam hems. One spec without the other is incomplete.
Why finer thread matters at the hem
The hem of a t-shirt is one of the first things you touch when putting it on. A heavy thread at the hem creates a raised ridge that's both visible from the outside and felt against the skin. On a quality garment, the hem should be barely noticeable — clean parallel stitch lines on the outside, flat and soft on the inside.
Tex 18 achieves this. The finer thread sits lower in the fabric, creates less surface bulk, and produces a more elegant stitch line. At the same time, it maintains enough strength for the coverseam structure — hems don't take the same stress as side seams, so you don't need the tensile strength of Tex 27.
Production specs for your tech pack BOM
| Spec | Value | Notes |
|---|---|---|
| Thread type | Corespun polyester | Same construction as Tex 27, finer weight |
| Tex size | Tex 18 | Also listed as Ticket 180 |
| Color | Match to fabric | Specify Pantone reference or "self color" |
| Application | Coverseam hems, topstitch | Bottom hem, sleeve opening, neckband topstitch |
| Machine | Coverseam machine | Not used in overlock machine |
In FlatLabs PRO, Tex 18 appears as a separate BOM line item from Tex 27 — clearly labeled by application so your factory knows exactly which thread goes on which machine.
A common spec mistake
Many first-time tech packs list "polyester thread" as a single BOM line item without specifying weight or application. The factory then uses one thread for everything — usually whatever is loaded. If that's Tex 27 on the coverseam machine, your hems will have a heavier finish than intended.
The fix is simple: list thread twice in your BOM — once for overlock (Tex 27, side and shoulder seams) and once for coverseam (Tex 18, hems and topstitch). Two lines, zero ambiguity, better quality control.