This is part of the Back to Basics Series of tutorials sponsored by Coats Crafts.   

Sew a Zig-Zag Hem for Jersey Fabrics

Preparation

 Iron your jersey fabric flat because it always has a tendency to curl.  Iron up your desired hem before stitching.  You need to iron jersey very gently to avoid stretching it.  

Sewing
 

Select zig-zag stitch on your machine.  Ideally you want to use a ball point needle when sewing jersey.  It prevents the jersey from laddering and stops the machine from skipping stitches.

Position your needle so one side of the zig-zag is just off the hem and the other side is on the hem.  You might want to practice on a scrap first.  Start stitching, being careful not to stretch the fabric as you sew. It always looks a little stretched when you finish sewing but a light press will improve the look.

I used thin jersey in this example so selected a number 9/70 needle and a wider stitch. You may want to experiment on a scrap first to find the right stitch width and needle for your fabric.  

 
Uses

This technique is useful for sewing any weight of jersey fabric or knit fabrics - t-shirt material, sweat shirt fabric - basically anything stretchy.