Knits and activewear stretch, and the machines have to stretch with them or the seams pop. Two machine types carry this work: an overlock to seam and finish stretch fabric edges, and a coverstitch for the flat, elastic hems and topstitching you see on T-shirts, leggings, and performance wear. The key feature on both is feed control. An overlock's differential feed gathers or stretches the fabric as it sews so knits don't wave, and a coverstitch keeps the hem flat and elastic so it flexes without breaking. JACK's E4S and C7 overlocks cover 3- to 6-thread finishing, with the C7 AI line auto-adjusting to the material; the K5 cylinder-bed and W4 flatbed coverstitch machines handle tubular and flat hems with thread-trimmer options. For activewear with elastic at the waist and cuffs, the coverstitch does the visible work. The overlock and coverstitch machines that build activewear are below, with full specs.
What to look for
Differential feed
On the overlock, two feed dogs move at different rates to gather or stretch the fabric so knit seams stay flat instead of waving.
Coverstitch for hems
The flat, parallel rows on a T-shirt hem come from a coverstitch — stretchy and clean on the face, covering the raw edge underneath.
Cylinder vs flat bed
A cylinder-bed coverstitch handles tubular cuffs and sleeves; a flatbed suits open hems and general topstitching.
Elastic attachments
Activewear waistbands and cuffs often need elastic attached under tension; confirm the machine supports the elastic and binding setup you run.
