The basic structure of sewing machine is the same whether it is hand operated, treadle, and electric sewing machines. The basic parts of sewing machine are listed below:
BED: Bed of machine is the base of the machine on which all the attachments are fixed.
BALANCE WHEEL/ FLY WHEEL: Balance wheel of the sewing machine is very important. It controls the operation of the machine. Unless this wheel is moved, the machine will not work.
BOBBIN WINDER: This holds the bobbin in position while winding the thread onto the bobbin.
BOBBIN-WINDER TENSION ANGLE: This is provided at the right- hand corner on the bed of the sewing machine. Thread is passed through this for winding the bobbin under uniform tension.
BOBBIN CASE: It holds the bobbin and is fitted into the shuttle. This moves into position to catch the top thread and form the stitch as the needle is lowered into the bobbin chamber.
CLUTCH/ THUMB SCREW: Located in the centre of the fly wheel. It engages and disengages the stitching mechanism. It is disengaged by turning in anti-clockwise direction, especially while threading the bobbin.
DRIVE WHEEL: It is a large wheel located under the bed of the machine. It is connected to the balance wheel by a leather band, thus transmitting the power which operates the machine.
FEED DOG: It refers to a set of teeth below the needle plate that helps to move the fabric in a backward direction while stitching. A reverse direction of fabric feed occurs when the stitch regulator is set in a reverse direction.
FACE PLATE: A cover that encloses the oiling points of the needle bar, presser bar and the take up lever.
NEEDLE BAR: This is a steel rod that holds the needle at the lower end. Needle is fixed by means of a clamp. Its main function is to give the needle the required motion. A groove is provided in the bar for holding the needle in appropriate position.
NEEDLE CLAMP: This clamp holds the needle in position on the needle bar.
NEEDLE PLATE/THROAT PLATE: It is a round or semi- circular steel plate, located below the needle bar. It has a hole to allow the needle to pass through reaching the shuttle to pick up the bobbin thread. The shape of the plate varies with the model of the sewing machine. There are markings provided on the needle plate that helps in guiding the cloth for stitching at the required width from the edge of the cloth.
PRESSER FOOT: It is fixed to the presser bar to hold the cloth firmly in position while stitching. Presser foot has to be lowered before the commencement of stitching.
PRESSER FOOT LIFTER: A lever attached to the presser bar helps in raising and lowering of the presser foot.
PITMAN ROD: This rod connects the treadle to the drive wheel, so that when the treadle is pressed, the drive wheel revolves.
PRESSURE-REGULATING SCREW: This screw is provided on top of the needle bar, which can be tightened for stitching finer fabric and loosened for stitching of thick fabrics. Its main function is to regulate the pressure on the fabric. Pressure should be such that it should not leave an impression on the fabric.
SHUTTLE: It is present below the machine bed into which bobbin case along with bobbin is inserted.
SLIDE PLATE: It is a rectangular plate which slides out easily. This facilitates the loading and unloading of the bobbin case into the shuttle.
STITCH REGULATOR: This controls the length of the stitch. Higher the number longer the stitch length. The length of stitches varies according to the type of fabric. Some of the machines have provision for reverse stitching.
SPOOL PIN: It holds the spool of thread.
TAKE-UP LEVER: This lever feeds the thread to the needle and controls the movement and flow of the spool thread and in the formation of stitches. The upward motion tightens the thread and the downward motion loosens the thread during stitch formation.
TENSION DISC: It comprises of two concave discs put together that controls the tension of upper thread. By turning it to the right or left, the tension of upper thread is can be tightened or loosened. The spring in the tension disc regulates the pressure.
THREAD GUIDE: A small hole made of spring wire holds the upper thread before being threaded into the needle.
TREADLE: It is situated under the machine bed. The machine can be started by peddling the treadle. It is essential for the sewing machine operator to have good coordination between the treadle and the fly wheel for smooth stitch formation.