i have used double needles lots on stained glass applique and have not had any problem breaking needles??? when would they break? was it hitting the foot (incorrect foot being used) or hitting the foot plate? or breaking going into the fabric?. they are expensive, i would be figuring out just what is breaking them, they should hold up even with fairly heavy fabrics. my mom uses her double needles all the time to hem denim jeans and she uses a universal, not a jeans needle. my thought is you are hitting something...a different foot with a larger opening may fix the problem.