The major components of a basic sewing machine include;
Stitch forming systems
The speed at which a machine can operate depends on the engineering of
1- The Casting
The machine casting is the metal form that provides the exterior shape to the
machine. Shapes of machine can vary according to the type of bed and the
sewing function that is to be performed and how piece goods are to be
prepared. The casting houses the internal workings that operate the sewing
and feeding mechanism.
The casting determines the bed type and location of the cloth plate.
Long Arm Flat Bed
Flatbed/ Fully Submerged Bed Types ideal for small parts and
where positioning parts to the needle is a "slide" from the tabletop.
Semi-Submerged Bed Machine for assembly of medium to large
Raised Bed Machines where the entire machine is mounted on the
top of the table. Used where you need the garment to drape away
from the needle for better handling.
Post bed machine where the needle plate and foot are mounted on a
tall post that facilitates sewing in tight spaces like inside sleeve
cap, or shoes.
Off-the-Arm Bed types facilitate sewing sleeve seams,
inseam or out seams on Pant Legs, or other long seams
in tight places.
Cylinder Bed Machines for sewing around the end of
Tubular Shapes such as Cuffs, Armholes and Round
Long Arm Flat Bed
Long Arm Flat Bed for sewing large objects (Quilts,
Upholstery, Flags, Sails, etc.)
Lubrication factors are the prime factors in
maintenance, downtime, efficient operations and long life time of various
parts of the machine. The mechanical parts of sewing machine like any
other mechanical parts are need to be lubricated (oiled) to reduce friction
and keep mechanical parts moving freely.
High speed and temperature increase the need for lubrication because of
There are two types of lubrication systems available.
In the former case oiling is done manually. In these machines no special
mechanism for oiling is present. These machines are also called as dry head
machines. The conventional sewing machine at homes is also an example in
which manually oiling is done.
In automatic oiling systems different parts work in combination with
each other to ensure the effective supply of oil to the required parts
Oil Gauge and oil sight window
Oil distribution network (oil pipes)
3-Stitch Forming System
Stitch forming system are the mechanical parts that when correctly
synchronized forms stitches, seams and then stitching.
Various stitch forming mechanism are:
Thread control devices ( thread guides and thread tensions).
Bobbin case, bobbin and hooks
Thread Control Devices
Thread control devices include thread guides, thread tensions and take-ups
which are necessary to provide uniform thread flow.
Thread guides control the position and movement of thread. Damaged or
faulty thread guides can damage sewing thread and cause thread breakage.
Tension devices controls the flow and tension in the thread going to form a
Tension in the thread determines the balance and tightness of a stitch.
Tensioning devices consist of a pair of tension disks, a spring and a thumb nut
that can be adjusted to control the ease with which thread passes between the
Thread take up control the supply of thread required to form each stitch. It
gives extra thread to the needle to form the stitch but takes it away to set the
Needles carry the thread through the fabric so a stitch can be sewn.
A hook is a rotating device encompassing the bobbin case that picks up the
needle thread loop to form a lock stitch.
Loopers are available in different shapes respective of their machines.
Looper may or may not carry the lower thread in the formation of stitch.
As in case of flat lock lopper holds the lower thread but in case of single
needle chain stitch it holds the needle thread.
Spreader work in conjunction with a looper to assist in the loop formation.
They in fact move the thread but did not carry the thread.
The material handling components of machine are also called as the feeding
system. For a precise line of stitches to be formed fabric must be moved
through the stitch forming area of the machine with accuracy and precision.
The feeding system usually consists of the following parts:
The presser foot
The throat plate
The presser foot
The presser foot is the upper part of the feeding mechanism. It is mainly
responsible for applying pressure and proper holding of the fabric.
The presser foot also controls the amount of pressure as if light fabric is being
sewed than more pressure will be implemented however if heavy fabric is
being sewed than pressure in the presser foot is lowered to some extent.
The throat plate
Throat plate is a metal plate that is present directly under the needle. Throat
plate has openings for needle and feed dogs.
Feed mechanism control the direction of fabric movement and the amount of
fabric movement for each stitch. Feed mechanism affect stitch length and the
rate of travel.
Lock Stitch Machine
A lock stitch is the most common mechanical stitch made by a sewing
A stitch made on a sewing machine by the interlocking of the upper
thread (Needle) and the bobbin thread.
Ideally, the lock stitch is formed in the center of the thickness of the
material—that is to say: ideally the upper thread catches the lower
thread in the middle of the material. The thread tension
mechanisms, one for the upper thread and one for the lower
thread, prevent either thread from pulling the catching point from out
of the middle of the material.
Over Lock Machine
An overlock stitch sews over the edge of one or two pieces of cloth
for edging, hemming or seaming.
Overlocking is also referred to as “overedging”, “merrowing” or
An overlock sewing machine differs from a lockstitch sewing
machine in that it uses loopers fed by multiple thread cones rather
than a bobbin.
Loopers serve to create thread loops that pass from the needle
thread to the edges of the fabric so that the edges of the fabric are
contained within the seam.
Stitch Formation Of Over Lock Machine
The upper looper is in its
rightmost position. The needle
begins its move from its lowest
position and as it rises, the
needle thread loop starts to be
In order to pick up the needle
thread loop, the lower looper
starts to move to the right from
its leftmost position.
The needle continues to rise
and the lower looper which
has picked up the needle
thread loop continues its
motion to the right.
The upper looper starts
The lower looper continues to
move to the right, the upper
looper picks up the lower looper
thread while crossing the lower
looper and continues to rise.
The needle is approaching its
The upper looper is at its
The needle has already started
to descend and enter the
triangle formed by upper
looper thread. The lower
looper has already started to
move to the left.
The needle is at its lowest
position, the lower looper is at
its leftmost position. The upper
looper continues to descend
Repeating this sequence of
actions form the seam.
Cloth is fed and only righthand needle is positioned in
the outside of decorative
thread. Two left-hand
needles come down and
scoop upper decorative
Needle further come down
and scoop lower looper
thread. And Two right-hand
needles enter in between the
respective needle threads.
Needle thread comes off
lower looper and needle
comes down in its lowest
position. Lower looper and
upper decorative looper are
in the most retracted
Feeding mechanisms are of 8 types
Adjustable Top Feed
Walking Foot Feed
(A manual feed is used primarily in freehand
embroidery, quilting, and shoe repair.)
When the needle is withdrawn from the material being sewn, a set of “Feed
Dogs" is pushed up through slots in the machine surface, then dragged
horizontally past the needle. The dogs are serrated to grip the material, and
a "presser foot" is used to keep the material in contact with the dogs. At the
end of their horizontal motion, the dogs are lowered again and returned to
their original position while the needle makes its next pass through the
material. While the needle is in the material, there is no feed action.
Differential feed is a variation of drop feed with two independent sets of
dogs, one before and one after the needle. By changing their relative
motions, these sets of dogs can be used to stretch or compress the material
in the vicinity of the needle. This is extremely useful when sewing stretchy
material, and overlock machines (heavily used for such materials)
frequently have differential feed.
A needle feed, used only in industrial machines, moves the material while the
needle is in the material. In fact, the needle may be the primary feeding
force. Some implementations of needle feed rock the axis of needle motion
back and forth, while other implementations keep the axis vertical while
moving it forward and back. In both cases, there is no feed action while the
needle is out of the material. Needle feed is often used in conjunction with a
modified drop feed, and is very common on industrial two needle machines.
Used mainly for Quilting purposes.
Adjustable Top Feed
The general arrangements of such feeding systems is that the presser foot is
in two sections, one holding the fabric in the position while the needle forms
the stitch and other having teeth on lower side and moving in such a way
that the top ply is taken along the positively while the needle is out of the
It can be used on the machines for light weight fabrics with no inter ply
Unison feed is a combination of feeding mechanisms which provide needle
feed in addition to positive top and bottom feeding.
It is used for operations on materials that have very low friction coefficients
and for operations that are very thick and heavy.
Usually accomplished by feed rollers. Material passes between rolls, between
upper roll and bed, or between lower roll and presser foot.
Commonly used in association with any other feed system. Generally suitable
for straight run or large radius curves.
A walking foot replaces the stationary presser foot with one that moves
along with whatever other feed mechanisms the machine already has. As the
walking foot moves, it shifts the work piece along with it. It is most useful for
sewing heavy materials where needle feed is mechanically inadequate, for
spongy or cushioned materials where lifting the foot out of contact with the
material helps in the feeding action, and for sewing many layers together
where a drop feed will cause the lower layers to shift out of position with the