What is the main function of the 4needle flatlock sewing machine?

Sep 01, 2025

A 4-needle flatlock sewing machine is known as flat seamer is widely used in the knitting wear, sports wear, socks, thermal underears etc, it is a type of covering stitch machine. Understanding its function is crucial to understanding its structure:

· 4-needle: This machine has four needles that work simultaneously, creating four parallel front seams.

· 6-thread: This machine uses six sewing threads. These six threads are:

· 4 needle threads (one thread per needle)

· 1 covering thread (looper thread)

· 1 lower looper thread

These four needles and six threads interweave and loop together, ultimately creating four parallel straight lines on the front of the fabric and two parallel, web-like cover seams on the back.

Main Functions and Features

Due to its unique stitch structure, a 4-needle, 6-thread sewing machine has the following main functions:

1. Efficient Joining and Sewing (Core Function): It is most commonly used to join two or more pieces of fabric together, completing seaming, hemming, and decoration in one operation. A single process completes what would require multiple steps (such as sewing, then hemming and curling) with conventional flat-bed sewing machines, significantly improving production efficiency.

2. Excellent elasticity and stretchability: The seam it creates is as resilient as a rubber band. When the fabric is stretched, the seam can extend with it without breaking. This is crucial for garments that require frequent stretching.

3. Smooth and comfortable seams: The mesh seams on the reverse side perfectly contain the rough edges of the fabric, creating a remarkably smooth and even seam. This seam is frictionless and feels like nothing, significantly enhancing wearer comfort.

4. Strong decorative effect: The four parallel lines on the front are neat and aesthetically pleasing, creating a strong visual decorative effect and often serving as a striking design element.

5. High strength and durability: Because multiple threads are interwoven and twisted, the seam is exceptionally strong, durable, and resistant to unraveling.

Main Application Areas

Due to these characteristics, 4-needle, 6-thread flatlock sewing machines are indispensable equipment for the following industries and products:

· Knitwear: The side seams and crotch seams of underwear, panties, bras, and shapewear are typically used for this purpose.

· Sportswear: The seams of sports bras, fitness wear, yoga pants, and swimwear must withstand significant stretch.

· T-shirts and sweatshirts: Commonly used for joining cuffs and hem ribbing to the body, as well as for sewing shoulder seams.

· Children's and infant clothing: Its smooth, boneless seams prevent chafing on delicate baby skin.

· Loungewear and pajamas: Similarly, they demand ultimate comfort.

Differences from Common Three-Thread Overlock Machines

Many people confuse this with an overlock machine, but there are essential differences:

Features 4-needle 6-thread sewing machine 3-thread overlock machine

Main Function: Joining, hemming, and decoration, all done in one go. Primarily performs hemming (to prevent unraveling) and sewing, but the joint strength is generally not as strong as a 4-needle 6-thread machine.

Seam Appearance: Four straight lines on the front, two mesh lines on the back.

One straight line on the front, one overlock line on the back.

Stretch: Excellent, designed for highly stretchy fabrics.

Good, but generally not as good as a 4-needle 6-thread machine.

Comfort: Completely flat and boneless on the back, extremely comfortable. Raised seams on the back may cause friction.

Application: Primarily used for functional stitching and high-end products. Widely used for overlocking and simple stitching of ordinary garments.

Summary

In summary, a 4-needle 6-thread sewing machine is a specialized machine for producing high-quality, highly stretchy knitwear. Its core function is to join fabrics efficiently, firmly and beautifully, and to create extremely smooth, comfortable and elastic seams. It is one of the "trump card" technologies in modern underwear, sportswear and other fields. If you want to buy a 4 needle 6thread flatlock sewing machines, please check and contact us freely.