What Is Overcasting in Sewing?

Use an overcast stitches on the cut edges of fabric prone to raveling.

When sewing, protecting the cut edges of the fabric is important to keep it from fraying, even if the cut edges are on the inside of the garment. Using an overcast stitch will protect the cut edges of the garment and make it look less "homemade." An overcast stitch combines straight stitching and a zigzag stitch where one point of the zigzag goes just over the edge of the fabric.

Types of Overcasting Stitches and their Uses

There are two types of overcast stitches that are done by hand; they prevent edges from fraying or are used as decorative stitches. One type uses a single line of stitching that loops around the edge of the fabric. Another uses a line of back stitching near the edge of the fabric, and a stitch that loops around the edge of the fabric. The back stitching helps to stabilize the fabric edge, while the stitch that loops around the fabric edge protects the edge from fraying.

When done by machine, overcast stitches are known as overlocking stitches, and they protect the fabric edge from fraying but can serve as decorative stitches when done in contrasting thread. Sewing machines or sergers may use one or more lines of stitching to protect cut edges, combining straight stitches and stitches that loop over the fabric edge.

Overcasting by Hand

Overcasting stitches by hand can be done with or without a row of straight stitches to help stabilize the fabric edge. Straight stitching is done using a back stitch 1/4 inch from the cut edge. The back stitch is performed by making one straight stitch, stitching backward for half the length of the previous stitch then making another stitch of the same length as the original stitch. The stitch that loops over the edge of the fabric begins 1/8 inch from the fabric edge and loops diagonally over the edge, similar to a whip stitch. If you work the stitch in both directions, it resembles a zigzag stitch.

Overlock on a Sewing Machine

Sewing machines offer an option that allows straight stitches and overcasting stitches to be performed at the same time. When done by machine, this is known as overlocking. Most sewing machine models overlock by creating a triangle of stitches -- one straight and two or more that zigzag over the edge. Not all sewing machines have this function. You can make your overlocking more neat by using an overlock sewing machine foot, which helps keep the fabric edge in place so that the zigzag stitches go over the fabric edge.

Overlock on a Serger

A serger is a machine designed specifically for overlocking fabric edges. Sergers may use up to five threads to stitch near and over the edge of fabric while trimming excess fabric. The overlocking stitches on a serger are especially useful for knit fabrics, which require seaming and edge finishing that can stretch with the fabric. Overlocking with a serger creates a sturdy, professional-looking edge finish that can serve as a hem.

References

• University of Kentucky; Seams and Seam Finishes; Linda Heaton
• Sew 4 Home; Finishing Raw Seams: Part One -- Sewing Machine Finishes; October 2009
• Sew 4 Home; Hand Sewing: The Basics; Alicia Thommas; May 2009
• University of Nebraska-Lincoln; Seam Finishes for a Plain Seam; Rose Marie Tondl; 1999
• Creative Sewing Tips.com: Hand Sewing Stitches
• Sewing and Craft Alliance: Seam Finishes - Part 2