When I had my SInger 2010 and had constant problems with it jamming, and i was ony sewing clothes...the repair man told me to use only Dual Duty Cotton covered polyester thread as regular or cheap thread causes so much fluff to collect in the bobbin cage. I bought that and used only that for 25 years and never a problem! But I just got a Singer 9960 for quilting I just started back up with, and it kept jamming and all and I looked and there the bobbin cage was..filled with thread fluff from the cotton/poly thread! I was shocked as that didn't happen on the 2010 machine. SO in just recently starting back at quilting and reading from this forum...I bought some 100% cotton thread from Connecting Threads.com and I just got it had started working with it yesterday until the rain/snow storm knocked out power and I haven't been able to get back to it, But I hope that is will work well. I am going on the mention that different machines like different threads! I hope this 9960 likes this thread!