The Sidewinder has a tension adjustment for tight or loose bobbin winds. You turn the round knob. It's in the instructions. My DGD used mine to fill a shoebox full of bobbins. She had a great time helping me in my sewing room. I took bobbins to guild for many months of all colors for handsewing/applique/bindings. I think I bought every package of bobbins Walmart had during the summer of "let me help you". Worth every penny!