Originally Posted by
deedum
They work great in my vintage machine when I was learning free motion! This days I don't need them, but yes I do like them! I will always keep some available if need them! They do have help with bird nesting or back lashing!
They are meant to eliminate back lashing......some machines at high speed will do that......if your machine works well without them or you can resolve the back problems by adjusting tension there is no need to use. Also, some bobbin threads which are thinner will backlash more frequently. jMHO