I tried to think of a cute title, but I couldn’t do it.
Down to business. Differential feed. I said you really did need this little function, now I’ll show you one (or two) reasons why. I use this adjustment all the time. I didn’t have it on my first serger and wow, it makes a huge difference.
To explain it is kind of tricky. There are two sets of feed dogs under the foot of a serger. One in front, one in back. The differential feed changes the ratio of these feed dogs. Look for a dial or knob or lever on your machine. It should be set at “0″ or “N” for the standard. It should be able to go “up” several steps to a “2″ or “down” 1-2 steps to a “0.6″. Your markings may differ, check your manual.
When the differential feed is turned “up”, it pushes in more fabric than it pulls through. Make sense? No? Thats okay. Its confusing. If its turned all the way up to 2, and the stitch length is at the longest possible, it will gather fabric. (please see below, while I continue to prattle on about it) Now……some caveats….this does NOT mean that you can take the skirt pattern piece and the bodice pattern piece, say “gather” and voila, it will all be good. The gathering ratio is *approximately) 2:1. Meaning if you have a 10″ strip of fabric, it should be 5″ coming out the other end. BUT, I have found this differs based upon fabric weight, type, where you hold your hands, time of day, how you hold your tongue and the current alignment of the sun, moon and stars. There are better ways to gather, which I will cover soon. However, this is great if you want to add a quick ruffle someplace, like the bottom of a dress, etc. Someplace that you can cut a long strip and not have to be exact.
After you finish adding ruffles to everything. Or perhaps, if you are not a ruffly type of person, maybe no where. You might wonder if there is anything else this adjustment will do. You are in luck! There is a very real life, everyday use for this feature! Its called knits (or any other fabric).
Have you ever sewed a knit across the stretch and it ends up bigger and kind of like a lettuce leaf? All curly? And you may try to press or steam it out or hope that after washing it will look better, but it never really does. Thats because the feed dogs have stretched out the fabric and then that stretch is sewn into place. Just great. Its one of the things that definitely makes things look “homemade” and not “handmade”. (one is good, one is not so good)
Just turn up the differential feed a bit. If you look at the sample below, one side was stitched normally, the other side was on a 1.4. See the difference? Which would you rather have in your sewing?
Now, there is no magically formula, each knit is different. Personally, I take a scrap, run it through and put it on a tabletop. If its flat, we are good, if its ruffly, the differential feed needs to go up.