How to Sew Buttons onto Knitted Fabric
Cardigan instructions simply tell you to sew on your buttons opposite the buttonholes. But a couple of refinements can help your buttons stay snuggly in their holes and keep your bands lined up neatly:
For a vertical buttonhole: Center both the button and the buttonhole along the center lines of the front bands. Then plot your button/buttonhole pair so that the center of the button lines up with the top corner of the buttonhole. This placement will discourage the button from sneaking free.
For a horizontal buttonhole: Don’t center both the buttons and buttonholes in the center of their respective bands. When you button your sweater, the button won’t stay centered in the hole; instead, the bands will pull apart until the button catches in the corner of the buttonhole.
Avoid this sliding problem by positioning the button away from the center, toward the outer edge of the band. When you button up, your bands will remain aligned one on top of the other.
For a stable button: When you sew your buttons on to a knitted piece, don’t be afraid to go into the yarn strands. If you try to secure a button by going around the strands and only in and out of the holes between stitches, your button will be unstable and will pull the stitch out of shape.
If you used a plied yarn for your sweater or project, you can unply a single strand and use it to sew on your buttons. You get a perfect color match. You also can use embroidery thread or simple sewing thread.
Most knitted fabric is dense enough to require a button with a shank — a small metal or plastic loop on the back of the button to sew through.