- 3-thread overlock machine: Straight stitch - Thread 1 (counting from left to right); Upper overlock thread - Thread 2; Lower overlock thread - Thread 3. Thread 2 interlocks with Thread 3 to form the edge of the fabric. When adjusting the thread tension, start with Thread 1 first.
- 4-thread overlock machine: Outer straight stitch - Thread 1 (counting from left to right); Middle horizontal stitch - Thread 2; Upper overlock thread - Thread 3; Lower overlock thread - Thread 4. Thread 3 interlocks with Thread 4 to form the edge of the fabric. Thread 1 is related to Thread 4. Adjust Thread 1 first, followed by Thread 2, then Threads 3 and 4.
- Overlocking without the cutting knife results in an uneven stitch. If the fabric is not fed straight (fed at an angle), the cutting knife will not cut evenly, causing an irregular stitch. A neat stitch requires both even fabric feeding and proper thread tension adjustment. If the fabric is not fed evenly or the thread tension is not set correctly, adjusting the thread repeatedly will not produce a correct stitch.
- Regularly use a small brush to clean fabric dust and oil the moving parts of the machine to ensure smooth operation and prevent rust. Every 6 months to 1 year, take the machine to a store for maintenance (cleaning, dust removal, rust treatment if needed). The maintenance cost outside the warranty period is usually a few tens of thousands of VND.

- When storing the machine, lower the presser foot lever to prevent loosening of the tension, which can cause uneven stitches.
- If the handwheel becomes stiff or the thread gets tangled, stop using the machine immediately; otherwise, the needle or the take-up lever may break.
- The upper thread may unwind and get caught on the thread stand, causing thread breakage.
- When starting the machine, run it from slow to fast speed.
- If the presser foot is not raised before threading, the thread will not properly enter the tension discs, leading to tangled or broken thread, and improper stitch formation.
- Loose tension (lower number) causes thread tangling and may break the needle. Tight tension (higher number) causes thread breakage.
- Thread tension: A higher number means tighter tension, while a lower number means looser tension. Turning to the right tightens the tension, while turning to the left loosens it.
- Types of needles: Needle size 11 - for stretchy fabric and dress pants; Needle size 9 - for thin fabrics; Needle size 14 - for denim and thick household fabrics.