Rolled Hem Operation Guide for Overlock Machine
Introduction
Rolled hem (micro hem / lettuce hem, namely the dense narrow serging in garment production) is a core finishing function of 3-thread overlock machines, widely applied to chiffon, silk, knitted jersey, swimwear and lingerie to form compact, curled, fray-proof fabric edges. Compared with standard overlock, rolled hem shrinks stitching width, shortens stitch density and adjusts thread tension to wrap raw fabric margin inward automatically for exquisite decorative edge finishing, which greatly improves garment grade and wear durability. Most industrial and household 3/4-thread sergers can switch to rolled hem mode via stitch finger retraction and parameter calibration.
1. Preparations Before Sewing
1.1 Thread & Needle Matching
Thread option: Use woolly nylon textured thread for upper looper to fill rolled edge plumply; ordinary high-strength polyester thread for needle and lower looper is the standard collocation. Woolly thread enhances fluffy decorative effect for elastic fabrics like lace and knit.
Needle specification: 75/11 fine needle for lightweight silk, chiffon; ballpoint needle for stretch knit; 90/14 needle for thin denim and thick woven fabric; replace blunt or damaged needles regularly to avoid skipped stitches and fabric pinholes.
Test cloth: Prepare leftover scraps same as production fabric to debug all machine parameters before formal sewing.
1.2 Basic Machine Pre-set
Shift rolled hem conversion lever to pull back the stitch finger completely; the stitch tongue under needle plate retracts to cancel edge support, enabling fabric edge inward rolling during feeding.
Retract movable trimming knife appropriately to narrow cutting width down to 2–3mm for ultra-narrow dense hemming.
2. Core Parameter Adjustment for Rolled Hem
2.1 Thread Tension Setting (Key Calibration)
Needle thread tension: 3.0–4.5 (slightly loose to prevent fabric longitudinal puckering)
Upper looper tension: 3.5–5.0 (moderate relaxation)
Lower looper tension: 6.0–8.0 (tighten obviously to pull upper looper thread wrapping to fabric bottom, forming curled edge)
Adjust gradually in 0.5 scale increment; if edge fails to roll tightly, increase lower looper tension properly.
2.2 Stitch Length & Width
Stitch length: 0.5–1.2mm for dense compact hem; shorter length for thick filled edge, 1.2–1.8mm for soft loose lettuce edge.
Stitch width: Minimize overlock width to 2–3mm after knife adjustment for micro rolled effect.
2.3 Differential Feed Ratio
Set differential feed between 1.3–2.0: higher ratio gathers fabric moderately to assist natural edge rolling; 1.3–1.5 for thin silk, 1.6–2.0 for stretch knit to avoid wavy over-puckering or flat non-rolling edge.
3. Step-by-Step Sewing Operation
Align fabric raw edge against machine edge guide, keep fabric flat without pulling or pressing forcibly by hand; excessive pulling causes uneven hem width and stretching deformation.
Start slow-speed stitching, keep uniform feeding speed; hold fabric lightly front and rear of presser foot to prevent shrinkage.
For curved edges (neckline, armhole), reduce sewing speed and swing fabric gently following radian to keep consistent narrow hem width.
Finish stitching, cut thread with trimmer and inspect finished edge: neat rolled curl without loose thread loops or exposed raw fabric.
4. Common Fault Troubleshooting
表格
| Fault Phenomenon | Root Cause | Correction |
|---|---|---|
| Fabric edge cannot roll flat | Lower looper tension too loose / differential feed too low | Tighten lower looper tension, raise differential ratio |
| Hem over-wavy & over-gathered | Differential feed excessive high | Reduce differential feed below 1.5 |
| Needle thread puckers fabric | Needle tension over-tight | Loosen needle tension dial |
| Loose thread loop on fabric bottom | Upper looper tension too high | Decrease upper looper tension value |
5. Application Scope & Maintenance Tips
Application Scenarios
Rolled hem is the preferred finishing for underwear hem, scarf edge, blouse cuff, swimwear trim, lace edging and fashion apparel decorative border; unavailable for heavy thick canvas and hard fabric with poor flexibility.
Daily Maintenance
Clean lint and thread waste inside looper and knife slot daily; add specified sewing machine oil to moving parts every 8 working hours to guarantee stable stitching and extend service life.