Some types of machine needles can be adjusted when the needles are combined with the needles. For example,   three-needle five-line interlock sewing machine can adjust the angle of the needle cam relative to the front section of the upper shaft  to adjust the timing of the matching of the needle and the needle. The best timing for the fit is when the right needle enters the needle loop when the needle is lowered and the needle begins to move to the right.

The swinging amplitude of the needle must ensure that the needle thread can be hooked when the needle is swung to the rightmost limit position, and the distance between the needle tip and the left needle is 4.5-5.5 mm when the needle is swung to the leftmost position. 

The height of the needle should be mounted as high as possible, but the gap between the top of the needle and the underside of the needle should be such that the needle thread passes smoothly.

The height of the needle threading plate should be such that the needle thread slides smoothly under the right needle to the back of the right needle tip (away from the operator side) when the needle is raised to the highest point, so that the right needle is lowered. Pin the needle thread easily.

When the tip of the needle swings to the front of the left needle, the gap between the left needle and the tip of the needle should be 0.5-0.8 mm.