Under normal circumstances, the common market tacking machine does not appear the sets long tacking offthe bottom line.

　　This case, it is recommended to loosen the bottom line, check the bobbin skew, the bottom line at whether there are glitches, oscillating shuttle axis wrap thread bobbins are wired paramount debris of these reasons may hinderthe bobbin rotation, affects the thread tension.

　　We might as well be placed shuttle remove cleaned or with oscillating shuttle machine operating normally puttry.