Perhaps the quilted cover that's coming apart is not so much a victim of bad thread as it is of the novice sewist that made it. It was the first thing I made and the first thing I made on my #1 treadle machine. I had trouble running the machine, I had trouble with the the tension, and I needed both feet and four hands to do what I needed to do. So in retrospect it's probably my lousy work that is causing the thread to break.
To the problem that instigated this thread. I like to use heavy thread such as the C&C Dual Duty XP HEAVY for heavy things such as a denim quilt. Those things are very heavy and I just don't want my seams to give way.
Like others I guess I believe in over kill.
So I've been using the C&C HEAVY thread and having troubles with it. Tension problems and birds nests.
I "think" I might have it figured out. I was using a size 14 needle. C&C says to use a 16 to 18 needle with that thread.
So, next time I set up to do some piecing I'll stick a 16 in it and go from there.
Joe