Hi Macybaby, Thank you for all your comments...do you use pre wounds or do you wind your own bobbins?
I have the Sweet 16 sit down quilting machine which I have had for a few years and only now I am having time to properly play with it.
I also have tension issues and have only used pre wounds to date but your idea of getting the towa tension gauge might be the way to go even though it is expensive as I want to enjoy my quilting and not be constantly playing with the tension settings.
To be fair some of my issues are probably with getting the hands moving in time with the machine and not going too fast around curves but it all takes practice so hopefully i too will get there one day where quilting is enjoyable for me.
I am only using rasant thread on top at this stage while learning as don't want to introduce more issues by using too many different threads.
To hopefully help others with my limited experience if your tension suddenly goes out after stitching fine, check the tension disks and make sure your thread hasn't jumped out of there or that there isn't a bit of fluff in there. Also check your thread that it hasnt caught up on something or wrapped itself around the spool holder etc. If still having issues check your bobbin holder as that may have a bit off fluff caught up in the bit where the screw is to adjust the tension. Use a pin to slide under there and push out any fluff.
Also after each bobbin change put in a couple of drops of oil in the bobbin area and remove fluff.