Singer has been making sewing machines since 1851, and over the years their machines have become easier to use. So, it's frustrating to sit down with a sewing project and find lumpy and loose stitches staring you in the face. Your Singer should run smoothly; if the thread isn't running through the fabric at an even pace there is something wrong with the tension on your machine. Whether you are working on a new or an old model, fixing the tension on those stitches needs only a few simple adjustments.
Check that your Singer is properly threaded. The instructions for each model are different. If you are not familiar with the Singer you are using, check the manual. If your machine is incorrectly threaded it might appear to be working, but will throw the tension off completely.
Make sure your bobbin was properly spun. The thread should lay flat and never overlap in a diagonal fashion when spun by a machine. Hand spun bobbins almost never distribute the thread evenly and will more often than not result in lumpy stitches.
Check that the bobbin was inserted into the latch lever correctly. The thread should be facing toward you, over the top of the bobbin, when inserted into the latch lever. If the bobbin was inserted upside down the tension will be too tight on one side and will eventually snap the thread.
Lower the lever or dial on your Singer to a lower number in order to loosen the tension and space out the stitching. It is advisable to use a lower tension setting for thick fabrics.
Increase the lever or dial on your Singer to a higher number in order to tighten the tension and decrease the space between the stitches. Thinner and more delicate fabrics, such as lace, should use a tighter tension.