are you using the correct size needle for your thread? also, like other's have mentioned- there is (sew-able) and (non-sew-able) heat N bond- heat n bond lite is the one you want- i would switch needles to a sharp or universal and make sure it is the correct size needle for the thread you are using- personally (and i've been sewing since the mid 60's) i've never had much luck with top-stitch needles- i use sharps or universals 99% of the time.