Older machines could wind bobboins without unthreading the machine, even wind while you were stitching. Newer machines have to be unthreaded to wind bobbins. The sidewinder is great for saving time. Have you seen the new ones, not $30, $100. Simplicity bought them and upgraded. Wish I could come up with an invention somebody would buy me out, then I could stitch all day instead of going to work!!!!