In daily life, when sewing with a machine, there will always be some winding problems, especially the winding problem of the sewing machine rotary hook. I am very confused. Now I have summarized 6 common problems: 　　　　
1. If the machine is used for a long time, the second thread clamp and the wire hook will grind out small grooves or form burrs, which will make the upper thread unsmooth and cause blockage. Because the 781 type upper thread is of low tension, this little block is enough to have a great effect on the tension of the upper thread.　　
If the tension of the second thread clamp is too high at this time, the thread is more likely to break. Generally, the thread breakage will be here, and the remaining upper thread will be wound around the hook; if the elastic force of the thread take-up spring is too small , Then the excess upper thread cannot be collected, and the stitch formation is unstable, and this phenomenon will also occur. In addition, it is worth noting that the spring force of the thread take-up spring of this machine should be slightly larger than that of the lockstitch machine.　　
2. Because the bobbin case has been used for a long time, the mating part of the shuttle door and the hook frame shaft is severely worn, causing the bobbin case to be out of the way, causing the upper thread to hook onto the bobbin case or hook to the bobbin adjusting screw on the bobbin case.
3. The bottom thread pulling pressure spring is damaged and deformed during use, especially when the tip is too close to the hook and touches the upper thread.　　
4. The position of the fixed knife of the bottom scissors is incorrect. Sometimes, in order to make the bottom knife can cut the bottom line well, move the lower knife to increase the "bite" between it and the movable knife. Since the fixed knife moves to the eye of the needle plate, the upper thread in the right column will break when the needle is buttoned, and the broken thread will be entangled with the hook.
5. If the noodle thread is too loose, the equipment is easy to roll the thread, and it is easy to wind on the shaft behind the hook.　　
6. Regarding the adjustment of the positioning hook, attention should be paid to the outside opening and the inside opening of the contact part of the positioning hook and the hook of the hook frame.
These six problems are often seen in sewing machine rotary hooks. Sometimes it is this kind of small problem that leads to errors in the sewing, so it must be solved in this way when sewing problems are encountered.

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