Thread, needle and stitch type are one setting. Too coarse a thread (and the needle it needs) cuts light cloth. Too fine a thread opens a stress seam. Elastane wants a stitch that can extend; a lockstitch wants a thread that will not dump elongation into puckers. TrimGem University teaches the match as garment engineering, the same way zipper gauge follows opening load. The Guangzhou sampling desk already sees thread next to needles and tapes; that set only grows with the catalogue.
The weight bands
Machine-maker tables (Brother and others) and mill practice agree on the direction:
| Cloth | Thread (indicative) | Needle | Stitch length |
|---|---|---|---|
| Light (chiffon, georgette, voile, some linings) | polyester Tkt 60–90; cotton/silk 50–80 | 65/9–75/11 | 1.8–2.5 mm |
| Medium (poplin, gabardine, light twill, linen) | polyester 60–90; cotton/silk 50–60 | 75/11–90/14 | 2.0–3.0 mm |
| Heavy (12 oz+ denim, canvas) | polyester or cotton ~30 | 100/16 | 2.5–4.0 mm |
| Knit / jersey | fine polyester, ballpoint needle | 75/11–90/14 | stretch stitch |
Needle NM rises as the needle thickens. Do not put a 20-ticket (very coarse) thread through a domestic-class machine; the eye and the groove are wrong.
Cotton-count shorthand used on Chinese lines: chiffon often 60s/2 or 80s/2 with a fine needle; shirting 40s/2 or 50s/2; 14 oz denim 20s/2 with NM 110/18-class needles on industrial heads. 402 polyester (40s/2) is the generic lockstitch default — generic, not universal.
Tension is fibre-specific
On a lockstitch, polyester often sits around a mid tension; cotton needs a little more or the stitch looks loose; high-stretch thread needs less or it sews in stretched and then snaps back into puckers. The check is visual: balanced stitch, no bobbin on the face, no needle thread in loops on the back. If bobbin shows on the face, ease needle tension half a number — after you confirm the ticket actually matches the needle eye.
Z-twist needle thread on lockstitch; mixing S-twist into that needle path snarls. Overlock loopers are a different twist conversation — put the construction the machine was cammed for.
Stitch type changes the thread
- Lockstitch (seams, topstitch): mid elongation, high abrasion on the surface stitch. Cotton or spun polyester tickets as the table.
- Zigzag / stretch lockstitch: finer or more extensible thread; shorter and wider bites on knits.
- Chainstitch and cover: loopers like textured polyester; they need extension. A stiff bonded nylon in a cover looper is skipped stitches.
- Buttonhole: abrasion first — a finer, denser thread or a dedicated gimp, not the cheapest spun.
- Crotch, shoulder, bartack: the strongest ticket that the cloth will still accept.
Match fibre family to the shell when shrink, heat and chemistry must travel together. Stretch garments want stretch thread and a stretch stitch. FR garments want FR thread. Colour and moisture regain should not fight the cloth.
Spec line
Fabric weight + needle NM/point + thread fibre/construction/ticket + stitch type + tension note. A tech pack that only says “match colour, polyester” is how a factory sews 20s/2 through georgette because that cone was on the machine.