You might be wondering what on earth it means when a serger is labelled ‘differential’. Let me explain. This is truly an awesome thing. Being a differential machine, this allows you control of the stitching stability on all types of fabric. When serging a cotton fabric, you will keep the machines differential setting in ‘neutral’.
The two extremes of the differential settings shown on cotton fabric.
Too tight and it pulls in the fabric, too loose and it becomes really wavy.
However, if you were to sew a knit fabric on the same setting, you will notice it become stretched and wavy, not sitting nicely at all. By changing the setting you have control over the tension of the sewing in this way also. As there are so many different variables, I simply suggest keeping a decent amount of scrap fabric from your sewing project, and running this through the machine prior to serging the actual garment. That was you know you have the tension right AND your differential feed right.
On a side note – did you know you can change your stitch length the same way you can on your regular sewing machine? Be sure to refer to your manual and search ‘stitch length’ to discover how to do this on your machine.
Disclaimer: Always refer to your own serger/overlocker manual for definitive advice on how to set up, thread and sew with your machine. I do not claim to be an expert on every model and thus am only sharing my personal experiences using two ‘lower end’ models (Toyota3400d and Janome1110dx).