25.
Regulating
the
Check
Spring
Action
The check spring assists the take-up lever in takirig up the balance of the
needle
thread
after
the loop has
passed
around
the bobbin,
and
further
in setting the stitch to the desired tightness ond in controlling the slack of
the
needle
thread
from
the time the
descending
t|ake-up
lever has drawn
the
thread
from the spool until the needle
reaches
the
goods.
Photo
24
The check spring is checked in its downward motion by a stop on its bushing
which
can
be
adjusted
as required. To do this, loosen
set
screw
s (Photo 24),
insert
o
screw
driver
into
the
slot
of
tension
stud
t
and
turn
the
stud.
Since thread regulator R (Photo
20)
is mounted on the presser
bar
lifting
bracket,
it moves up
and
down with the presser
bar
as
the sewing
foot
passes
over
irregularities in thickness. With this motion it regulates the
amount
of
thread
which
varies
with the inequalities in thickness
of
the
material
and
complements the action of the check spring so that it
does
not
have
to
take
up
excess
slack
thread.
Vertical
adjustment
of the
thread
regulator is
made
possible
after
loosen
ing
screw
u (Photo 20). It
has
the
same
effect
on
the
thread
control
as
turning the check spring bushing. For
best
results, it is
recommended
to
coordinate
both
adjustments
so
that
the
check
spjring
will
not
only
take
up
the correct balance of the thread but also
draw
up the thread perpendi
cularly.
28
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