Troubleshoot - For knits (t-shirt, stretchy), use ballpoint needle. Will say "for knits" on pkg. Wrong needle for the wrong fabric (i.e. a woven needle while sewing knit fabric) = problems. If you can see two separate threads, you probably have a tension problem. If you can see bobbin thread on the top (needle side) of your fabric, lower the needle tension. If your needle thread (see photo below) is being pulled to the bobbin side of the fabric, increase the needle tension.