Safety-edge overlock 504
Also known as: 504 overlock, 3-thread overedge 504, safety edge stitch
Classic three-thread overlock per ISO 4915 stitch class 504 — secures the cut edge, stretches with the seam and is standard in almost every knit and activewear garment.
Description
Stitch type 504 belongs to ISO 4915 stitch class 500 (overlock stitches) and is a three-thread overedge stitch: one needle carries the needle thread, two loopers (upper and lower) interlace its loops around the fabric edge. The result is a very elastic, tidy edge finish that also prevents the cut edge from fraying.
504 is the most common seam construction in cut-and-sew garments: it joins side and shoulder seams on T-shirts, sweatshirts, hoodies, jerseys and sportswear, as well as sleeve and hem edges. Combined with a 401 double-lock chainstitch (on the same machine), it forms the "true" safety-stitch seam ISO 516, familiar for example from denim inseams.
- 3 threads: 1 needle + 2 loopers
- Highly extensible (ideal for jersey, fleece, activewear)
- Secures the cut edge against fraying
- Combined with 401 → ISO 516 safety-stitch seam
Properties
| Stitch class | ISO 4915 class 500 — stitch type 504 |
|---|---|
| Threads | 3 (1 needle + 2 loopers) |
| Extensibility | Very high — ideal for knits/jersey |
| Application | Side/shoulder/sleeve seams, edge finishing |
| Combination | With 401 → ISO 516 safety-stitch |
Related product categories
Sources & references
2- Wikipedia: Overlock Wikipedia — Freie Enzyklopädie https://en.wikipedia.org/wiki/Overlock
- American & Efird: Stitch-Type Matrix (PDF) amefird.com https://www.amefird.com/wp-content/uploads/2009/10/Stitch-Type-Matrix.pdf
