When I bought my 930 Bernina many years ago we had a different tension from the top tension when we did embroidery and put the thread in the little hole in the bobbin thingy that sticks out, My new 830 has basically the same procedure, If you have a book with your sewing machine it may tell you about what you need to do about it, for the different kinds of sewing . I was also told to buy prewound bobbins or use serger thread in the bobbin because it is finer or use the same embroidery thread, Also sew a sample and look at the threads , Looking at the sewn threads can tell you if you need to change the bobbin tension or the top tension, the new 830 Bernina has a larger , flatter bobbins so prewound will not work, I also clean my machine after every bobbin fill. Keeps the machine clean and no little fuzzies, I sew just about every day, :XD: