Methods and Considerations for Selecting Sewing Machine Needles for Industrial Sewing Machines

When purchasing sewing machine needles, it is common to mention needle sizes denoted by the letter "X", which represents the needle gauge specification. A needle gauge is used to distinguish different sewing machine needles by indicating their needle shaft diameter. Sewing machine needle gauge specifications are expressed in three different systems: Numbered, Metric, and Imperial.

The Numbered system, often referred to as the "Tex system," is based on the numbering system developed from the American Tex sewing machine component numbering. It is the most common method for indicating needle gauge, with larger numbers corresponding to thicker needles. In the Metric system, the needle shaft diameter is measured in hundredths of a millimeter. The Imperial system is similar to the Metric system but measures the needle shaft diameter in thousandths of an inch.

Needle specifications such as "needle shaft diameter," "needle shank diameter," "needle eye to point length," and "needle overall length" have tolerance ranges, which are typically +0.22" for the needle shaft diameter, +0.22" for the needle shank diameter, +0.2" for the needle eye to point length, and +0.2" for the needle overall length. Table 1 reflects the variation in needle thickness and needle gauge between high and low ranges. Historically, to improve needle strength and meet the demands of high-speed sewing, there have been variations in the thickness of needles in the high and low ranges. However, with advancements in needle materials, processing methods, and the need to sew challenging fabrics, needles with minimal variation between high and low ranges are becoming more common.

The representation of needle gauge varies in different regions. Typically, Japan uses the Numbered system to indicate needle gauge, Europe uses the Metric system, and the United States uses the Imperial system.

Manufacturers that use different systems for indicating needle gauge will provide information on the interchangeability of needles in their product catalogs. Users are advised to follow the manufacturer's product documentation for proper needle selection. For example, in the case of Organ needles from Japan, needle gauges are represented by odd numbers like 5, 7, and 9. A size 5 corresponds to Metric size 45, size 7 to Metric size 55, and a size 9 to a Metric size 65. While these sizes can often be used interchangeably, variations of 1-2 millimeters may exist within a certain size range (e.g., within 100 gauge units), but this does not affect normal use.

When selecting needles to pair with specific threads, users can refer to the compatibility between needle gauge and thread size. This correspondence is usually determined by each manufacturer, and users should match needles and threads correctly based on the manufacturer's product documentation. Below is an example illustrating the correspondence between needle gauge (Organ needle) and thread size for different types of sewing threads.

When pairing needles and threads, the general principle is to use thicker threads with thicker needles and thinner threads with thinner needles. Sewing machine needles and threads often experience issues related to needle and thread compatibility, so it's essential to consider thread characteristics. Currently, commonly used sewing threads in garment production include pure cotton, polyester-cotton blends, mixed fibers, polyester, and synthetic silk. These threads are typically composed of two, three, four, or six strands of single yarns twisted together, with twisting directions designated as S-twist and Z-twist. If the thread twist is too pronounced, it can cause thread looping, affecting stitch formation. To check the twist, take a one-meter length of thread and hold both ends together to see if the natural twists in the two strands are less than six twists. If it exceeds six twists, it is more likely to result in skipped stitches. When sewing thin and soft fabrics with fine needles, it is necessary to increase the needle lift amount. When friction is low and the lift interval is constant, a narrower thread loop width can affect normal loop formation and may lead to skipped stitches. Conversely, when sewing thick and stiff fabrics, the opposite adjustment may be needed, requiring a change in the relative positions of the hooking mechanism and the needle.