1. Sewing of synthetic fiber: Since synthetic fiber thread is more prone to skip stitches than cotton thread, the hook thread time position should be slightly delayed. The most suitable time position of the hook is 2.2-2.6 mm, and the most suitable position of the needle is that the tip of the hook is about 1 mm above the needle hole. In order to prevent the sewing material from wrinkling, it is necessary to lower the tension of the bottom thread and the upper thread as much as possible.
2. Sewing of thick materials: When sewing thick materials, thick needles and thick threads are generally used, and the rotary hook must also be suitable for these conditions. If the shuttle frame is made slightly higher than the ordinary one (0.5-0.6 mm), enlarge the needle groove and increase the hook thread. Therefore, when installing the rotary hook into the sewing machine, please bend the hook holder positioning hook slightly and install it at a slight offset.
3. Sewing of knitted fabrics: Due to the greater elasticity of the knitted material, the loops of the upper thread are more difficult to form, and the stitches are prone to skipping. In order to prevent stitch skipping, the position of the needle can be adjusted to a position slightly lower than the standard. Also, delay the synchronization of the needle and the hook (thread hooking time) appropriately, use a needle plate with a smaller needle hole and a presser foot with a slot to pass the thread, and use the thinner needle as much as possible. In this way, the resulting sewing effect is better.

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