Darning width adjusting device for sewing machine

A darning width adjusting device for a sewing machine, wherein the sewing machine cuts an edge of a workpiece fed to a stitch point by an upper knife and an lower knife arranged at an upstream side of the stitch point in a cloth feeding direction, the darning width adjusting device for a sewing machine comprising:

• a lower knife holder which holds the lower knife and supported by a sewing machine frame such that a moving position of the lower knife holder is adjustable in a direction orthogonal to the cloth feeding direction;
• a thread-sliding piece which sets a darning width by picking up a thread on a tip of the thread-sliding piece in a vicinity of the stitch point;
• a thread-sliding piece holder which holds the thread-sliding piece and supported by the sewing machine frame such that a moving position of the thread-sliding piece is adjustable in the orthogonal direction to the cloth feeding direction from a first position providing the narrowest darning width to an outside marginal position providing the widest darning width;
• a thread-sliding piece adjusting means for moving the thread-sliding piece holder such that the moving position of the thread-sliding piece is adjusted from the first position to the outside marginal position;
• and
• a lower knife holder adjusting means for adjusting the moving position of the lower knife holder from a position corresponding to the first position of the thread-sliding piece to another position exceeding a position corresponding to the outside marginal position of the thread-sliding piece.