Serger Thread

Definition and Overview

Serger thread is used for overlock sewing to form stitches by combining needle thread and looper thread. In addition to overedge stitching to prevent fraying at fabric edges, it is also used for applications such as sewing and edge finishing at the same time in knits and similar materials.

Whereas a standard lockstitch machine forms stitches with upper and lower threads, a serger uses multiple threads. For that reason, thread stretch, bulk, and thread tension stability affect the appearance and strength of the stitch.

Materials, Twist, and Structure

Serger thread includes polyester spun thread and nylon or polyester filament thread. Spun thread is made by twisting together short fibers, and it is widely used from general woven fabrics to knits.

When stretch and softness in the stitch are needed, textured thread or woolly thread with added bulk may be used in the looper. Woolly thread spreads out easily and covers the stitch, making it suitable for products that require a soft hand and good stretch recovery.

However, even for serger use, material, twist, and processing are not uniform. Needle threads are chosen for strength and smooth feeding, while looper threads are chosen for coverage and stretch, depending on their role.

How Thickness Is Expressed

Thread thickness is shown by count or nominal count. Count is one way to indicate thread thickness, but because there are different notation systems, numbers alone cannot be compared directly across different thread systems.

In sewing thread, nominal count is sometimes used as a manufacturer or distribution standard. Even with the same nominal count, thickness, stretch, and finished appearance vary depending on the material, whether it is single yarn or ply yarn, and whether it has been processed, so it is easier to confirm details when the specification lists the material, structure, and color together.

Main Applications

The main applications are seaming and edge finishing for knit products such as cut-and-sew garments, underwear, and sportswear. It is also used for preventing fraying at the cut edges of woven fabrics and for seam allowance finishing on the back side.

The number of threads used varies by stitching specification. The required properties of the needle thread and looper thread also differ depending on whether the main purpose is edge finishing, stretch retention, or increased stitch strength.

• Overlock finishing of woven seam allowance edges
• Seaming and edge finishing of knit fabrics
• Reinforcement of stitches in stretch materials
• Creating soft stitches for underwear and sports applications

Selection and Sewing Precautions

Select thread according to the fabric material, thickness, stretch, stitching specification, and the product’s use environment. If a low-stretch thread is used on a stretchy fabric, thread breakage or tight seams may occur during wear. Conversely, if a bulky thread is used on a thin fabric, the seam may appear thick.

On a serger, adjust the needle size, differential feed, presser foot pressure, and thread tension to match the thread and fabric. If the looper thread does not fully cover the seam allowance edge, or if the thread is pulled too tight, check not only thread tension but also thread thickness, compatibility with the needle, and sewing conditions.

Before mass production, sew test samples with the same number of layers as the actual fabric and check stitch stretch, puckering, thread breakage, and appearance after washing. When matching colors, it is important to confirm not only the fabric surface but also the appearance of thread at the seam allowance edge.

Differences from Similar Terms

Sewing thread is a broad term for all sewing threads, including those for home use and industrial use. Serger thread refers specifically to thread mainly used on a serger. However, because thread itself is not always limited by application, machine compatibility and sewing specifications must be checked.

Woolly thread is a thread given stretch and volume through texturizing. It may be used as a type of serger thread, but not all serger thread is woolly thread. Overlock refers not to the name of the thread, but to the stitching method used to edge-finish fabric or to the type of sewing machine.

Frequently Asked Questions

Can serger thread and regular sewing thread be used interchangeably?

In some cases they can, but it depends on the fabric and sewing specification. Regular sewing thread may be used for overedge finishing on woven fabrics. On the other hand, for knits and stretch materials, using textured thread or woolly thread in the looper makes it easier for the stitch to follow the fabric’s stretch.

Should the needle thread and looper thread on a serger be different?

They may be the same, but they are separated depending on the required performance. Needle thread is expected to provide strength and smooth passage through the needle eye, while looper thread is expected to provide coverage over the seam allowance edge and stretch. When changing thread, always check the stitch with test sewing.

What should be checked when thread breakage occurs on a serger?

Check whether the thread tension is too strong, whether the needle is worn or bent, and whether the needle size matches the thread thickness. In addition, the threading path, looper timing, differential feed, and presser foot pressure relative to the fabric can also cause thread breakage or skipped stitches.