Stitch Types, Seams and Finishing
This domain tests stitch classification, seam classification, seam allowance practice and finishing operations - the vocabulary the exam uses when it asks which stitch or seam suits a given fabric and load.
Stitch classes (ISO 4915)
- Class 100: single-thread chain. Class 300: lockstitch, e.g. 301 single-needle lockstitch.
- Class 400: multi-thread chain, e.g. 401 two-thread chain for strong, stretchy seams.
- Class 500: overedge - 504 three-thread overlock, 514 four-thread overlock with two needles.
- Class 600: cover stitch, used on hems and binding. Blind hem 103 and buttonhole 304 are also common.
Seam classes and types (ISO 4916)
- Class 1 superimposed (plain seam), Class 2 lapped (lap-fell), Class 3 bound, Class 4 flat (flat-fell), Class 6 edge neatening.
- French seam for lightweight and sheer fabrics; run-and-fell and flat-fell for shirts, jeans and workwear.
Allowances and finishing
- Standard side seam allowance about 1 cm, overlock edge about 6 mm, hem 1.5–2.5 cm as per spec.
- Backtack 3–4 stitches at the start and end, finishing just inside the seam edge, not beyond it.
- Trim thread tails to about 3 mm; check for puckering and pleating before the piece moves on.
- Lock overlock chain ends or run them back into the seam.
Worked example
A denim inseam is specified as flat-fell. Reasoning: the seam is lapped so raw edges are enclosed, and two rows of stitching spread the load - necessary because the inseam takes high stress and is visible when the cuff is turned.
Traps
- Mixing up 504 (three threads, one needle) and 514 (four threads, two needles).
- Backtacking past the seam edge, which puckers and shows on the face.
- Leaving overlock chain ends unlocked so the seam opens after washing.