① There are burrs in the pinhole of the threading needle. If the thread is cut off, the threading needle can be replaced with a new one.

② There are burrs in the tooth shape of the front plate of the bookshelf or burrs in the lower part of the needle bearing plate. If the thread is cut off, the burrs should be polished and smooth.

③ The hook claw has burrs or the hook claw has friction with the front plate or the back plate of the bookshelf. If the line is cut off, the burrs of the hook claw should be smoothed or the position of the hook claw should be adjusted.

④ If the wire pressing disc is too tight or the wire pulling lever is too tight, the wire breaking shall be caused by loosening the gear ring to adjust the spring pressure and the time to start pressing.

③ The hook claw swings too late and the reset action is too slow, resulting in the disconnection caused by the hook claw of the hook thread needle not returning immediately or the hook claw returning too slowly to take off the thread. You can adjust the position of the control cam where the thread hook claw swings, turning it through an angle.

⑥ If the thread is broken due to the failure in the middle of the transmission line, the yarn tube should be laid flat, and some paraffin wax should be applied frequently to increase lubrication to reduce the thread breakage. If the quality of the yarn itself is not good and the fastness is poor, the yarn should be replaced with a new one.