First, open the needle board, press down the needle bar and hang it into the driving block, manually rotate the shaft to 196 degrees (it must be accurate), loosen the screw of the lower dead center, adjust the height of the needle bar, make the upper end of the needle hole within the range of 0.5- 1MM from the lower end of the hook tip, lock the lower dead center (be careful not to rotate the needle bar), and rotate the shaft to1mm. If it is too loose, the needle won't come out), and then check whether the front and rear plane positions of the needle are correct. Over.