Definition
A twin needle is two machine needles on one shank that sew two parallel rows of stitching on top with a zigzag underneath, mostly to hem knits.
A twin needle fits most sewing machines that can sew zigzag, since the needle plate opening must be wide enough for both needles. It uses two spools of upper thread and one bobbin: the bobbin thread zigzags between the two needle threads on the wrong side, which gives the stitch a little stretch.
Twin needles are labeled with two numbers, the distance between the needles and the needle size, such as 4.0/75 (4 mm apart, size 75). Common types are universal, stretch (for knits), jeans and embroidery, in spacings from about 1.6 to 6 mm.
Settings and tips:
- Use a straight stitch with the needle in the center position, lengthened to 3 to 3.5 mm.
- Put the two spools on separate pins and follow your manual for passing the threads through the tension discs.
- Sew from the right side. A strip of wash-away stabilizer or light fusible tape under the hem prevents tunneling, the ridge that forms between the rows.
- Loosen the upper tension slightly, or use woolly nylon in the bobbin, for more stretch.
- If you choose a zigzag, keep it narrow enough for both needles to clear the plate; many machines have a twin-needle setting that limits the width.
Beyond knit hems, twin needles make decorative topstitching and raised pintucks (see tuck). The machine-made alternative is a coverstitch; for allowances, see hem.