Serger setting
A serger control that changes the relative speed of the front and rear feed dogs.
Increase the ratio so the front dogs deliver more fabric than the rear set removes.
Move toward neutral or slightly below it, while also checking pressure, stitch length, and cutting width.
High ratios can gather; low ratios can intentionally stretch an edge for lettuce finishes.
Useful distinction
Differential feed changes fabric movement. Thread tension controls how loops form, so treat the controls separately.
Practical guide
Numbers are ratios, not universal recipes. The useful setting is the one that lets the actual fabric leave the presser foot flat, unstretched, and without unintended gathering.
The front feed dogs collect fabric before it reaches the needles, while the rear feed dogs carry the stitched fabric away. Above neutral, the front section moves more fabric forward and counters stretching. Below neutral, the rear section removes fabric faster and deliberately stretches the edge.
Cut two scraps on the same grain as the project and serge one at neutral without pulling. If the edge waves, raise the ratio one step and repeat with the same stitch length, cutting width, and pressure. Compare cooled samples on a flat surface rather than judging them while stretched behind the machine.
A high ratio can compress a fabric that did not need help. Return toward neutral before changing thread tension. Also check whether a short stitch length, tight needle threads, or excessive presser-foot pressure is drawing the seam together.
A high ratio and longer stitch can gather a light woven edge for ruffles or easing. It is controlled fullness, not a substitute for gathering threads when an exact finished length is required. Test how much the sample shortens and divide longer pieces into matching sections.
Avoidable mistakes
Common questions
It is commonly marked 1.0, N, or a center line, but scales vary.
Pressure, stitch length, fabric handling, or extreme stretch may still be contributing.
Yes, especially on light fabric with longer stitches and a high ratio.
Most do not; it is mainly a serger or overlocker feature.
