I use Coats and Clarks Quilting thread its, the STAR Machine Quiling & Craft thread in the big spools 100% cotton and have never had a problem. You might also want to change your machine needle and see if that doesn't help your problem. I do not like the polyester or some of the Gutterman polyester threads as I've had them fruzz up and break often when quilting. Stick to 100% cotton thread as I think you'll be much happier in the results.