We are fortunate to have so many different types and weights of thread from which to choose. Selecting the best thread for the project will provide a visible improvement in the finished product. Remember that the needle and thread work together as a team and they must be compatible with each other as well as with your fabric choice. Do not assume that thread companies maintain the same standards year after year. There are a number of brands whose quality assurance has fallen by the wayside and their products are no longer as dependable as they once were.
Tension is the balance of pull between the upper or needle thread and the lower or bobbin thread.
The stitches should meet exactly in the middle of the fabric layers for perfect tension. If you do not have a perfect straight stitch, odds are no other type of decorative stitches or buttonholes will be properly formed. Hold your hands at each end of the stitching and give a quick, firm snap to the fabric. Occasionally, the bobbin tension will have to be adjusted slightly. You may want to know how to make this adjustment if you are planning to use decorative threads in your bobbin.