The needle plate and the feeding teeth of the medium speed machine are double rows, and the force on the second half is larger. When the operator uses the sewing machine with an inverted feeding wrench to do the inverted feeding operation, it is easy to inject. If the phenomenon of injection occurs, the needle plate will collapse. If the needle plate with good quality is not easy to appear this phenomenon.
Inspection method: Place the screwdriver in the feeding alveolar of the needle insertion board, and shake it left and right, carefully observe whether the force is deformed, such as deformation is inferior.