What is the problem when after sewing a straight line, I can pull the bobbin thread and it comes right out like I had done a gathering stitch, but I hadn't. It happens whether I do a long stitch or a short stitch. I have had this same thing happen on 2 other machines.

It sounds like your top tension is way to loose. It is not pulling the bobbin thread into the middle. Here is a link to a great graphic from superior threads to help you. http://www.superiorthreads.com/educa...bottom-tension

Have you tried tightening your upper tension?

Gee I'm having same problem! I've tightened tension also!!

Ty for the help. The info helped me!!

Check to make sure your thread is in the tension disks correctly. Or maybe the tension disks need to be cleaned. a piece of lint can keep the disks apart so it is loose. You can run a thread with several knots through the disks and that should take out anything in there.

Rethread the machine. It sounds like you have NO tension at all.

Is your presser foot lever down/engaged?

I take a piece of dental floss to clean the disks out in the machine...Just thread the machine with the floss and gently pull back and forth a couple of times.

Good idea!