Feed dogs move fabric beneath the presser foot. Their toothed bars rise through slots in the stitch plate, grip the lower layer during part of the stitch cycle, and advance it by a controlled step.
Feed movement and stitch length
The presser foot holds the layers against the feed dogs with suitable pressure. The selected stitch length affects the distance travelled at each stitch: a short stitch uses a small feed step even when the machine is running quickly.
Fabric should normally be guided without force. Pulling, pushing, or holding it back can make stitch length uneven and may bend the needle or damage the plate.
Lowering the feed dogs
Many sewing machines allow the feed dogs to be dropped so the operator can move the work freely, as in free-motion quilting or darning. On some models, the teeth do not re-engage immediately after the control is reset; turning the handwheel or starting a stitch completes the mechanism’s cycle.
Solving uneven feeding
Because ordinary feed dogs act on the bottom layer, long seams, slippery surfaces, thick stacks, or pattern matching can cause the upper and lower layers to creep apart. Presser-foot pressure, an even-feed or walking foot, and built-in dual feed can improve control. At a bulky seam crossing, a height-compensation tool keeps the foot level so the teeth can retain their grip.
An overlocker normally has front and rear feed-dog groups. Differential feed changes their relative travel to counteract stretching or puckering, or to create intentional gathers.