The principle of adjusting the front and rear needles is: the front and rear needles should be aligned with the needle tip from the operator's direction. In order to prevent the needle from being shaken on the needle, the needle is close to the needle side. Should be properly chamfered. The front needle (near the operator) needs to act as a needle guard and at the same time block the sewing thread from forming a loop in front of the needle eye (close to the operator), so that the loop behind the needle eye can be smoothly formed. The rear needle should not only play the role of the needle but also prevent the smooth formation of the loop.

Due to the difference between the manufacturer and the machine model, the shape of the front and rear guard pins and the allowable adjustment range are somewhat different from the ideal state, requiring the maintenance personnel to move as close as possible to the principle to be followed.

When the needle moves down, the front and rear needles move away from the needle. When the needle is raised from the lowest position, the front and rear needles are moved toward the needle.

When the needle is lowered to the needle position, the needle should be removed from the needle to avoid scratching the needle.

When the curved needle tip moves to the left to the right needle position, the front and rear needles start to function. The gap between the needle and the needle in front (close to the operator side) is 0.1-0.3 mm, and the rear needle and the needle are The gap between them is 0-0.1 mm.