I own this exact machine. First, there is not a way to adjust the bobbin tension thread to my knowledge. There is not a typical screw and bobbin holder. The bobbin drops into the base. I have learned that if you run a stitch off of your material, the bobbin thread "jumps" but still looks like it is in place. It is necessary to pull the bobbin out and reinsert. I also know that it is better to take a scrap and start on that and then feed your actual quilting piece into the machine OR hold BOTH threads back when you first start sewing. I have also had problems with deco stitches....I am going a long fine then all of a sudden the stitches start messing up in the middle of a quilting project.*** Not a great machine.***