The Garment Sewing Machine

Parts of the Sewing Machine: The principal parts of an average sewing machine are illustrated below. Although the sewing machines may differ slightly, there are many similar features.

Domestic slot type sewing machine

Industrial dial type sewing machine

1.      Balance Wheel/ Hand Wheel/ Fly Wheel – This is said to be free wheel. This wheel balances the movement of sewing machines. It balances the stitching; the movement starts from the shuttle driving rod, the needle bar, connecting rod. This is a very important part of the sewing machine. The balance wheel should always turn towards the operator, if not, the upper thread breaks immediately. There are two types of balance wheels – light weight or thing balance wheel and heavy weight of thick balance wheel.

The heavy weight balance wheel is fixed on low speed sewing machine and the thin balance wheel is fixed on high speed sewing machine. The main purpose of this wheel is to cause the movement for both the needle driving rod and the shuttle driving rod, this wheel is connected to the crank wheel by the means of a belt.

2.      Bobbin winder assembly – It is fixed by the side of the balance wheel, it is meant for winding the bobbin by means of the thread. This part contains a small rubber wheel and a small steel rod. As soon as the rubber wheel is pressed it touches the balance wheel and begins movement for winding of the bobbin.

3.      Stitch regulator assembly – It gives number of stitched per inch. Mainly there are two types – dial type and marked (slot) type. The dial type is mostly fixed on a high speed sewing machine. It is controlled by pin or a clutch. It is operated with clockwise directional movement according to the length of the stitch required. The marked type is fixed in a stitch regulator slot to regulate the stitch length. The thumb nut and the regulator should be adjusted, greater the distance between ‘0’ point and the thumb nut, larger the stitches that is number of stitches per inch.

4.      Needle bar assembly – This is richly polished rod made of special steel. This holds the needle at the bottom with the help of needle screw and clamp. The needle bar is placed near the presser bar and this bar is fixed to the needle bar driving shaft by means of a clamp. The balance wheel which takes the movement from the crank wheel passes the movement to the needle bar driving shaft, thus causes the upper thread to move the upper material.

5.      Presser foot bar – this is fixed at the side of needle bar. This bar has links at the bottom or top. The presser foot is linked at the bottom and the presser string linked at the top by means of a thumb nut called pressure regulating screw. The presser bar is controlled by a lifter called presser bar lifter; through this part pressure is applied to the material which is placed for sewing.

6.      Needle clamp – Needle clamp is fixed at the bottom of the needle bar by means of a clamp nut. The machine needle is fixed in this needle clamp. It has a thumb nut, by loosening which the needle can be removed and in the same manner the needle can be fixed in position by tightening the screw. There are two types of needle clamps – circular (in industrial sewing machines) and flat (in domestic sewing machines).

7.      Presser foot – This foot is a shoe shaped component which is fixed to the bar by means of a screw. It applies pressure to the stitching material directly and makes the material move backward and forward. The presser foot is controlled by means of a thumb nut.

8.      Presser foot lifter – This is a lever attached to the presser foot bar to control the up and down movement of the presser foot. It is attached to the bar at the centre position by means of a spring and screw. To remove the material from the sewing machine the presser foot must be lifted by means of presser foot lifter.

9.      Face plate – It is a highly polished plate fixed at the left side of the head of the sewing machine. The face plate envelopes the pressuring bar, needle bar, thread take-up lever and protects them from dust and lint. The tension disc is fixed on the face plate which controls the upper thread tension.

10.  Thread take-up lever – This is an important working part of the sewing machine. This is fixed to the needle bar driving shaft. At the outside end of the lever there is small hole through which the thread passes. The take up lever feeds the upper thread to the machine needle by taking the thread via the tension disc. If the upper thread does not pass through the lever, seams are not formed. There are two functions of this lever; to feed the thread to the needle and to tighten the thread through the loop formed by the bobbin

11.  Needle thread tension disc – To control the needle thread there are 3 units fixed on the face plate of the sewing machine; the tension spring, the tension disc and the thumb nut. The tension of the upper thread can be increased or decreased by loosening or tightening the thumb nut. This controls the movement of the upper thread which has to pass through the tension disc before entering the eye of the needle. The tension has to be adjusted well according to the lower thread tension. The tension disc is a simple mechanism where two concave discs are put together by facing the convex ends to each other.

12.  Thread guide – This is a small hook fixed on the face plate through which the upper thread runs up to the needle in the vertical direction. It holds the thread in position from the spool to the needle.

13.  Throat plate or needle plate or lock plate – It is a semi-circular plate with polished surface and a hole to allow the needle to pass through. It has slots through which the feed-dog works. The main purpose of this plate is to provide surface level for the cloth and to prevent the cloth from entering directly into the shuttle slot.

14.  Spool pin – It is located on the machine arm to hold the spool of thread in domestic machines and on separate rods behind the machine to hold the thread cones in case of industrial machines.

15.  Bobbin winder – It facilitates the winding of the thread to the bobbin. Some bobbin wonders have a stop motion when the bobbin is full.

16.  Slide plate – This is a rectangular plate which can be opened to insert the bobbin in the shuttle.

17.  Feed dog- The purpose of the feed dog is to move the fabric forward to a pre-determined distance between successive needle penetrations, thus forming a seam. The amount of movement of the material after the completion of each stitch also aids in setting the stitch and in drawing in the required amount of bobbin thread from the bobbin. The shape of the feed dog and the arrangement and size of the teeth are important both in relation to the fabric and to the operations. Generally large teeth are required for thick fabrics and smaller teeth for fine fabrics.

18.  Bobbin case – This moves to catch the top thread to form a loop or stitch with the bobbin thread. It is placed below the needle plate.

19. Needle – Is the main sewing element in stitching garments. The basic function of the needle is to penetrate the material without damaging it and to provide a hole through which the needle thread may pass, to carry the upper thread down through the material and form a loop in this thread through which stitch forming element can enter at appropriate time.

Sewing machine shapes

In fashion manufacture the machines are still predominantly used in their basic forms but, for more specialised garments and those made in higher volume, variations in machine shape are available which enable easier movement of the materials around the machine. These variations primarily affect the shape of the bed of the machine, i.e. the part on which the materials rest. The best known versions are as below:

1.Flat bed machine – The large working area allows a wide range of applications; the material can easily be guided around the needle and the presser foot. This basic type is used for all kinds of sewing, lockstitch and chain stitch.

2.       Raised bed machine – The bed plate is in the form of a plinth. It facilitates the assembly of pre-sewn parts and is especially suitable for the fitting of accessories and special attachments. This is the basic form for various specialised machines such as buttonholers, T-shirt hemming etc.

3.       Post bed machine – This type has an increased working height, with working area of 2”X2”. Special applications are found in the working of three dimensional (3D) products e.g. shoes, bags, caps etc. the post makes it easier to work on tight curves and corners, to sew in sleeves and to complete large half-assembled products.

4.       Cylindrical (horizontal) bed machine – This type has an increased working height and a bed in the shape of a horizontal arm. It is especially suitable for working on tubular parts such as cuffs, sleeves and trouser legs.

5.       Feed-off-the-arm machine – Is used where a lapped seam has to be closed in such a way that the garment part becomes a tube. They are common in jeans production where the outside leg-seam is normally the type known as lap-felled and it is joined after the inside leg seam in the sequence of construction. The operator wraps the part to be sewn around the machine bed and it is fed away from him, off the end of the bed, as he sews.

6.       Side-bed machine (over edge) – machines which are specialised for sewing at edges need only a small working area. These have a blade attached next to the needle bar for neatening the fabric edge. Used to give chain stitch and Over lock stitches.