Interesting and timely topic. I was just at my repair shop for my Topaz 30 Viking on Saturday. My repair man said it is perfectly OK to use serger thread in the bobbin when doing embroidery. I was surprised to hear this as I thought I had to use bobbin thread in the bobbin. Does anyone use it in the bobbin when doing embroidery? I have bobbin thread to use up, so haven't tried it yet. Thanks.