The inability of a sewing machine to automatically cut threads is usually caused by loose mechanical connections, inaccurate thread cutting timing, or electrical control system failures. It is necessary to sequentially inspect the mechanical components, adjust the cam position, and check the circuit.

The correct repair method for skipped stitches of the stretch sewing machine is to follow the principle of "check before adjustment", and systematically check and adjust the key links such as threading, machine needle, crochet (looping needle) synchronization, needle protection, and suture tension one by one. ‌‌

The size of the needle code (needle pitch) for overlock sewing machine adjustment mainly depends on the machine type, and is divided into two adjustment methods: mechanical and computerized. Before operation, it is necessary to ensure that the machine is in a stopped state.

Flat sewing machine is a specific type of sewing machine, mainly used for straight stitching. Sewing machines are a broader category that refers to all machines used for sewing materials.