It is very important that you have the correct tension when you sew in order to ensure the seams will not come apart. An incorrect tension can result in a puckered seam that can ruin the entire look of the finished garment.
Different fabrics will require different settings, so always test the machine tension on a scrap piece of fabric before sewing the garment. When setting the correct tension, it may be helpful to thread the machine with different color threads to better be able to see where the top and bottom stitches link together. That way you can see at a glance which tension needs adjusting.
To adjust the tension, simply move the tension dial to a lower or higher number. The tension dial determines how much thread is released into the stitch as it is made; too much tension results in not enough thread, and not enough tension results in too much thread being released. If you’re not sure where the tension dial is, consult your owner’s manual.
When you have the correct tension, your stitch links, the area where the top and bottom threads are joined together, will appear evenly between the fabric layers. The stitches will be even on both sides of the fabric resulting in a professional look.
When you have too much tension, a result of not enough thread released in each stitch, the fabric will pucker and the stitches may be uneven. Also, the stitch links will appear near the top layer of the fabric. To fix the problem, turn the tension dial down until the stitches come out even.
When you have too little tension, a result of too much thread released per stitch, the stitches will be loose, thus creating a weak seam. The stitch links will appear toward the bottom layer of fabric. To fix the problem, turn the tension dial up until the stitches come out even.
Setting the right tension can be frustrating if you new to sewing. The key is to make small changes in the tension until you are more familiar with it.