Originally Posted by
leggz48
I'm using Superior threads so I know it is quality;
The manufacturer of the thread is no assurance that there isn't a problem with the thread. Superior brand Rainbows and Highlights are both known problematic threads, prone to shredding and breaking. So much so that Superior has discontinued Highlights. These threads need a lower than normal upper tension setting. They like almost no tension.
Additionally I have know superior threads to have a defective cone now and then. Even the best manufacturers can have a mishap.
Try changing needles and threads, test the machine, if the problem goes away, then go back to the problem thread. If you continue to have shredding and breakage you may have a defective spool/cone of thread. If the problem persists with other threads, time to take out your bobbin case and carefully inspect as well as turning your hook assembly manually and feel for rough spots. A burr on the bobbin case or hook can also cause your upper thread to shred and break but it will do it after only a few stitches. You can smooth them out with an emory board type fingernail file.