How to adjust the needle protector of the overlock sewing machine?

Taking a brand of the overlock sewing machine as an example, the author introduces the standard adjustment of the needle guard height and clearance of the machine. If there is anything wrong, please correct it.

01 During single needle and double needle sewing of overlock sewing machine 

① When the lower bending needle hooks, the needle guard A slightly contacts the needle to make the needle bend 0~0.05 mm (Fig. 1).

② When the needle is at the bottom dead center, the clearance between the needle guard B and the needle is 0.1mm.

③ The height of needle guard B is 1mm below the needle plate.

Adjustment method:

① When the lower bent needle tip reaches the center of the needle crown, unscrew the needle guard plate screw 1 for adjustment, so that the needle guard plate A slightly contacts the needle, and the needle bends 0~0.05 mm.

② When the needle bar is at the bottom dead center, unscrew the needle guard screw 2, and turn the needle guard B to make the clearance between it and the needle 0.1 mm.

③ Unscrew the needle guard B screw 3 so that the clearance between the needle guard B and the needle plate is 1mm.

Change of adjustment value:

① Strong contact between needle guard A and the needle will make the needle bend and jump.

② There is a gap between the needle and the needle guard plate A, and the needle and the bent needle collide, which may cause a broken needle or damaged bent needle.

③ If the needle guard B is too high, the bent needle and double link chain will jump.

④ The needle guard plate is too low, and the cooling and needle guard are affected because the needle cooling oil consumption is reduced.

⑤ The gap between the needle guard board B and the needle is large, which will cause needle skipping due to excessive needle swing. The gap is small, which will clamp the needle, causing wear on the needle guard board and damage to the needle.

02 During safety sewing of the overlock sewing machine 

During safety sewing, there are 4 needle guard boards A, B, C, and D. A and B are the same as the overlock sewing. The height of the needle guard is 5mm below the needle guard (Fig. 2).

Adjustment method:

① Unscrew the needle guard plate screw 4 for adjustment and let the needle guard plate C slightly contact the needle so that the needle is bent by 0~0.05 mm.

② The installation height of needle guard C is adjusted to 5mm by unscrewing screw 3.

③ Unscrew screw 5 for adjustment so that the clearance between the needle guard B and the needle machine is 0.1mm.

Note: Confirm the height of needle guard C, and then confirm the clearance between the needle guard B and the needle.

Change of adjustment value:

① If the height of the needle guard plate C is too high, it will collide with the bent needle and cause needle skipping; The needle guard C is too low and will damage the needle tip.

② The clearance between the needle guard plate C and the machine needle is too large, and the double loop chain sewing curved needle collides with the machine needle, causing the broken needle or the broken curved needle. If the clearance is too small, the needle guard plate will be strongly contacted, causing wear and breakage of the needle.

③ The clearance between the needle guard plate D and the needle is too large, and the needle swing is prone to needle skipping. If the clearance is too small, the needle guard plate will be worn and the needle will be broken.