you said you are using Superior Thread- but not what kind or weight...if it is 40-60 wt cotton thread a size 14 needle is too small. which could be fraying the thread. often the labels on superior threads tell you what size needle to use- if the thread you are using does not have that information on it visit their website & look it up- they have charts showing what needles to use with each thread they carry. my 100wt thread says to use a size 14 needle & loosen the top tension a slight bit. we can maybe give more help/ideas if we know what thread you are using- cotton? poly? rayon? silk? blend? and what size/wt. and --- when was the last time you changed needles? if your needle is dull, bent, has a burr, threads will break too. my *fix suggestions* would be---- change to a larger needle, loosen the top tension just a little, slow down the machine speed and see if that helps-