How a
Sewing
Mact.ine
Functions
Household sewing machines all make
the
conventional lockstitch.
This
type
of
stitch consists
of
on upper (needle)
and
a lower (bobbin) thread locked together ·
in
the material being stitched. The lock
of
threads
is
pulled to the middle
of
the fabric so
that
the seam has the same
appearance
top
and
bottom.
Every sewing machine designed to produce this type
of
stitch must hove
the
following component ports
and
assemblies:
1.
a needle
2.
a sewing hook, complete with bobbin
case
and
bobbin
(typical
of
any lockstitch sewing machine)
3.
a take-up lever
.
4.
an
upper
and
a lower tension mechanism
5.
a feed
dog
6.
Stitch forming
and
feeding mechanisms
7.
a bobbin winder.
The
Needle
In
contrast to
the
hand sewing needle, the machine sewing needle has
the
eye
near
its tip.
It
penetrates
the
material
at
every stitch, carrying the
thread
down through the hole it has mode
in
the
fabric.
As
it rises
after
reaching
the
lowest point
of
its stroke, the thread bulges
out
on the short-groove side
of
the needle to form a loop
above
its eye. This loop
is
entered
ot
the correct
time by the point
of
the shuttle
or
sewing hook (figs. 1 &
2).
l
1
Fig. 1
Fig. 2
Sewing machine needles
are
available
in
many different varieties
and
sizes,
and
are
classified into several groups,
or
systems.
7
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