When I bought my Viking a few years ago I remember being told NOT to use Coats & Clarks thread, EVER. It is simply not made the way it used to be. I now use 40 or 60 wt. polyester embroidery thread. Isacord is my favorite for piecing and you can get the king spools online for about $7.00 for 5000 yds. It is strong and thin and makes for more accurate piecing and fewer bobbin changes.