Have you ever hemmed a t-shirt or finished an overlock edge on high-stretch lycra leggings, only to find the seam rippling into a wavy, stretched lettuce edge? Or conversely, seen lightweight fabric curl into unintended puckers?
The solution lies in mastering your overlock machine's differential feed system.
How Differential Feed Works
Unlike lockstitch machines which feature a single unified feed dog, an overlock machine has two independent sets of feed dogs:
- Front (Differential) Feed Dog: Grabs the fabric first as it enters the needle zone.
- Rear (Main) Feed Dog: Carries the fabric past the needle and out the back.
The differential feed ratio lever adjusts the stroke speed of the front feed dog relative to the rear feed dog.
Setting the Differential Ratio Lever
- Neutral (1.0 Ratio): Both front and rear feed dogs move at the exact same stroke length. Used for standard non-stretch woven cottons and linens.
- Gathering / Anti-Stretch (1.5 to 2.0 Ratio): The front feed dog moves faster and feeds MORE fabric into the needle area than the rear dog takes away.
- Use Case: Eliminates wavy rippled edges on stretchy jersey, rib knit, rayon, and lycra fabrics by pre-compressing fabric fibers before the needle penetrates.
- Stretching / Anti-Pucker (0.7 to 0.8 Ratio): The front feed dog moves slower, gently holding back lightweight slippery fabrics.
- Use Case: Prevents puckered seams on lightweight nylon, micro-polyester, and silk linings.
