2. Difference in hooking time when the thickness of the sewing material changes

One of the key elements of adjusting the sewing machine is to adjust the so-called hook line time. The usual adjustment standard is: when the needle is lowered to the lowest position, when the needle is lifted up by 2.2 mm, the tip of the needle reaches the center line of the needle, 2 mm from the upper edge of the needle hole. Of course, this is not static. Because the purpose of adjusting the hooking time is to make the hook tip hook the upper thread when forming a perfect and stable optimal loop, thereby avoiding the jumping phenomenon. Since the thin material is generally used as a thin thread, the stitch itself is soft and the friction with the sewing material is small, and when the thick material is thick, the thick thread is generally used, the stitch itself is relatively stiff, and the friction with the sewing material is relatively strong. The force is large. Therefore, when the thickness of the sewing material is different, the time for the stitch to form the optimal loop is different. This requires that the hook thread be flexibly adjusted according to the specific conditions to obtain the desired sewing effect.

Experienced sewing machine repairers and operators know that when sewing thin materials, the tip of the shuttle should be adjusted "fast"; when sewing thick materials, the tip of the shuttle should be "slow". The reason is not difficult to understand.

When the thin material is sewn, the suture is fine and soft, and the needle is slightly raised from the lower limit position, and the loose suture is swollen to both sides of the needle to form a loop. Moreover, since the friction between the sewing material and the suture is small, when the needle continues to lift upward, the relative positional relationship between the sewing material and the suture is relatively random, and the stitch is soft and the loop is easily deflected, making it difficult to maintain stability. Therefore, a slight advance adjustment of the tip of the shuttle with respect to the needle helps to improve the reliability of the hook line.

On the contrary, when the thick material is sewed, the sewing material is thick and stiff, and the needle can be raised from the lower limit position to form a full wire loop. Moreover, the friction between the sewing material and the suture is large, and the sewing material is relatively thick, and even if the needle is lifted higher, the sutures are more abundant, and the loop is not deflected, and the stability can be maintained. Therefore, it is