My singer quantum stylist 9960 bobbin case squeaks while sewing the stitches are fine its just sounds terrible

the small flat spring on the bobbin holder under which you pull the thread is the tension setting for bobbin thread
it extremely delicate and just a partial turn of the screw that holds that spring in place has a large influence on the tension
mostly problems here are that the needle tension is insufficient and causes the problems

Here is a link to the instruction manual, if you can do a reset it will be in the manual, if not then it is not an option http://www.singerco.com/uploads/download/1242_9960_esf.pdf

the movement is set in reverse
change the setting to forward

Do NOT oil!!

You need to have the bobbin case replaced. I had mine replaced under warranty.

Customer Support ,,,,

http://www.manualowl.com/m/Singer/9960-Quantum-Stylist/Manual/321682

Classic burr on the hook problem would be my first guess. If the thread remains on the hook when it makes the next revolution all sorts of ugly things happen such as you described. I made a video that might help.

I'm looking for a solution to why the thread cutter isn't working. It just pulls the thread into a knot and jams the bobbin case. I was hoping for an answer here but the answer had nothing to do with the question!