Buttonhole darning sewing machine

摘要

A cloth cutting knife 16 is structured such that the length of the cutting edge thereof is set shorter than the length of the side sewing portions of a buttonhole to be formed, and a buttonhole having a length corresponding to the length of the right and left side sewing portions can be formed by moving up and down the cloth cutting knife 16 two or more times. The cloth cutting knife 16 is moved up and down at least once during formation of the stitches of the right and left side sewing portions. Also, the cloth cutting knife 16 is moved up and down once each time a given number of stitches of the right and left side sewing portions are formed. The given number of stitches is set in accordance with both of the length of the cutting edge of the cloth cutting knife 16 and the length of the buttonhole to be formed.