Modern sewing machine come in a variety of styles and offer many options besides simply sewing. Some double as serger or embroidery machines. Some have hundreds of different stitches, while others have just a few. Regardless, the major parts that allow a sewing machine to sew are the same.
The foot control is the pedal that sits on the floor and controls the sewing machine motor. The motor does not move the needle until the foot control is pressed, although electricity to the machine is turned on with a switch on the side. This allows you to control the machine with your foot while guiding material through the machine with your hands, starting and stopping as often as you need.
The pressure foot holds the material for sewing and guides it through the machine. The needle stitches through (or next to) the foot and into the fabric. Pressure feet come in different shapes to accommodate different stitches or functions. The straight stitch pressure foot has a single vertical opening up the middle to allow the needle through, but the zigzag foot had a wide, horizontal opening that allows the needle to move from side to side. With the zipper foot, the needle stitches on the outside, allowing you to sew the close seams zippers require. A clear plastic pressure foot allows you to see more of the material beneath the foot as it's stitched. This can be useful when applying top stitching or decorative touches to a garment. It's important to use the right foot for the stitch you want to make--the needle will break if it hits the foot. Switching to a different foot is as simple as pressing the release button at the back of the arm the foot attaches to and clipping a new foot in its place.
Thread Tension Control
The thread tension control balances the tension of the thread coming from the spool on top with the tension of the thread coming from the bobbin underneath. Numbers on the dial between 0 and 9 serve as a gauge, with 5 as the median. Uneven tension can cause your seams to pucker or become loose. A quick examination of the seam will show if the tension is off and adjusting the tension control dial will compensate. If tension is too low, the stitches on the underside of the fabric will look and feel bumpy. If it is too high, the top stitches will look or feel bumpy. High tension can also cause the thread to snap in the machine.
Modern sewing machines come with dozens of programmed stitches. Even models without computerised components offer a large number of stitches. Dials or buttons on the front of the machine allow you to choose the type of stitch that matches your project. Most of the "extra" stitches are decorative stitches you can use to add accents to the fronts of garments. Some, like the stretch stitch, smocking stitch or button hole stitch, serve a specific purpose in constructing a garment.
Stitch Length and Width Controls
Sewing machine stitches can vary in length and width. The straight stitch has no width, but does have length, and the dial on the front of the sewing machine allows you to control it. The standard length for a stitch is 2, but some materials require smaller stitches to prevent fraying, so lengths vary between 0 and 4 or 5. The highest length is used for basting fitted seams together with long (temporary) stitches that will later be resewn with a shorter length stitch. The stitch width control is used for stitches such as the zigzag that move from side to side. This setting also varies between 0 and 5 on most models. Many of the decorative stitches a machine can do rely on both the length and width controls to create the specific stitch.