Definition
A coverstitch is a stretchy stitch with two or three parallel straight rows on top and a looped thread underneath, used to hem and topstitch knit fabrics.
Look at the hem of a store-bought T-shirt: two neat lines of stitching on the outside and a mesh of loops inside, covering the raw edge. That is a coverstitch. It stretches with the fabric without breaking and gives knits a professional finish.
It is made by a coverstitch machine, or by a combination machine that converts between serger and coverstitch. Unlike a serger, it has no knives: the hem is folded up and the raw edge is caught by the looper on the wrong side.
Typical setups:
- Two-needle narrow, about 3 mm (1/8 in) between rows, for light knits.
- Two-needle wide, about 6 mm (1/4 in), the classic T-shirt hem.
- Three-needle, for activewear and sweatshirt hems.
- Chain stitch, one needle and the looper, for a stretchy single row.
Coverstitch is also used to topstitch neckbands, attach elastic and, with a binder attachment, bind edges in one pass.
On a regular sewing machine, the closest equivalent is a twin needle, which makes two rows on top and a zigzag underneath. It stretches less and can form a ridge on thin knits, but works well with a little practice. For hem allowances and other techniques, see hem.