When industrial sewing machines are sold, the upper thread and the lower thread will be threaded first. Remember the position of the manufacturer’s thread installation, and generally do not change it. The thread threaded by the manufacturer must be the best when it is sold. If it is changed later, it may affect sewing. When threading the upper thread, we first put two reverse twisted threads and one positive twisted thread on the upper thread in order. Seen from the position of the operator, the leftmost needle is a reverse shuttle, which uses positive twisting, and the other two needles in the middle and the right are positive shuttles, which use reverse twisting.
The thread guide, thread take-up, and thread tensioner can all adjust the tension of the upper thread.
When changing the bobbin, run the needle to the position where it can pierce the cloth. At this time, pay attention to the hook tip of the hook thread to be at the bottom, then twist the lower shuttle stopper, and take out the bobbin case. Replace the bobbin with a full thread, return the lower shuttle stop to the original position, and finally check whether the bobbin cover and the position of the shuttle stop are installed correctly..