Sewing Machine Thread

Definition and Overview

Sewing machine thread is thread used for sewing apparel and fashion accessories together. In general, it is used in lockstitch machines for both the needle thread and bobbin thread, and it affects seam strength, appearance, and sewing stability. Topstitch thread is a name for sewing machine thread used mainly to join fabric within the seam allowance.

Even with the same sewing machine thread, suitability differs depending on the material and thickness of the fabric to be sewn, whether the stitches will be visible, and the type of sewing machine used. Thick stitching thread that shows the seam as decoration and thread for serger machines have different applications and required properties from general sewing machine thread for joining seams.

Materials and Twist / Structure

Materials include polyester, cotton, nylon, and silk. Polyester is widely used because it offers a good balance of strength, abrasion resistance, and ease of handling. Cotton thread blends well with cotton fabrics, and silk thread is chosen when gloss and texture are to be emphasized. Materials are also selected with consideration for the fabric's appearance, dyeability, and resistance to washing and friction.

Thread is made as spun yarn, which is produced by twisting short fibers together, or as filament yarn made from continuous long fibers. There is also core-spun thread, which has filament at the core and short fibers covering the outside. Twist is the process of combining fibers to give strength and dimensional stability, and the direction of twist may affect machine rotation and seam condition.

• Check gloss, fuzz, and texture to match the surface feel of the fabric.
• For stretch materials, combine thread and stitching methods that can provide the stretch needed for the seam.
• When product washing, dyeing, or heat treatment is performed, also check color difference and shrinkage after processing.

How Thickness Is Expressed

The thickness of sewing machine thread is indicated by thread count or nominal thread count. Thread count is a unit that expresses thread thickness, but because the meaning differs depending on the notation system, the number alone cannot be simply compared with thread in another system. For sewing machine thread, the nominal thread count used by each maker or standard may also be used as a practical selection code.

In general, within the same notation system, a larger thread-count number indicates a finer thread. However, the apparent thickness and strength vary depending on the number of plies, material, and processing. In specifications, adding the material, color, usage location, and, if necessary, the sewing machine needle and stitching method to the thread count or nominal thread count helps prevent misunderstandings.

Main Applications

For topstitching, it is used for joining body panels, sleeves, collars, seam allowance finishing, and attaching facings and accessories. For thin fabrics, a finer thread that is less likely to damage the delicacy of the fabric is often selected; for medium-weight fabrics, thread that balances seam strength and workability; and for heavy fabrics, thread that can more easily secure the necessary strength.

For stitches where the seam is shown on the surface, thicker thread than for joining seams or decorative thread may be used. On the other hand, overlock sewing uses serger thread that forms the seam with multiple threads, and embroidery uses embroidery thread that emphasizes color development and gloss. These are threads for specific applications and are selected separately from topstitch thread.

How to Choose and Sewing Precautions

As a basic rule, choose thread that matches the fabric color, but check not only the outer fabric but also the lining, interfacing, and overlapping seam allowances. On dark or highly saturated fabrics, even a slight color difference may stand out. Before mass production, carry out test sewing with the actual fabric, needle, machine, and sewing conditions to confirm the appearance and strength of the seam.

If the thread tension is not correct, seam puckering, tight seams, loops, and thread breakage can occur. Rather than trying to solve the problem with thread alone, adjust the needle thickness and tip shape, upper and lower thread tension, feed amount, sewing speed, and stitch type together. Test sewing is especially important for knit fabrics, thin fabrics, and coated fabrics.

• If the thread is too thick for the fabric, it may lead to puckering or prominent seams.
• If the thread is too thin, it may be difficult to obtain the strength and durability needed for the seam.
• For specifications where the seam must stretch, check not only the thread's elongation but also the seam structure.
• If there are needle damage, skipped stitches, or thread breakage, check the needle-thread combination, needle damage, and machine settings.

Frequently Asked Questions

Does sewing machine thread need to be made from the same material as the fabric?

It does not always have to be the same material. Select it based on the fabric's appearance, the required seam strength, stretchability, and downstream processes such as washing and dyeing. For example, even with cotton fabric, polyester thread may be used to improve sewing stability. For areas visible from the surface, confirm color, gloss, and how well it blends with the fabric through test sewing.

Is sewing machine thread with a larger thread-count number thicker?

If the thread count uses the same notation system, a larger number generally means a finer thread. However, sewing machine thread includes multiple notations, including nominal thread count, and the material and thread structure also differ. Do not compare thickness or strength with thread from other systems based only on the thread-count number; confirm through specifications, sample cards, and test sewing.

How are topstitch thread and stitching thread different?

Topstitch thread is thread used mainly for seams that join fabric. Stitching thread is intended to emphasize or decorate seams that are visible on the surface, and thicker thread or thread with decorative qualities is used. If stitching thread is used for topstitching, needle holes, puckering, and stiffness may stand out depending on the fabric, so use them according to the application.