fitting an ironing board cover_cutwork tablecloth

Heavy duty machines typically have higher maximum sewing speeds, around 1500 stitches per minute, versus 1000-1200 stitches per minute for standard machines. Again, this allows them to work through heavy fabrics more efficiently. However, heavy duty machines also tend to sew better at slower speeds, in the 500-800 stitch per minute range, for optimal control through thick seams. So they provide a wider speed range to suit the fabric.