Singer 1640 - Page 18

Section
4
CHECKING
TENSION
OF
LOWER
THREAD
If
you
are unable
to
balance
the
stitch
by
adjusting
tension
on
the
upper
thread,
you
may
have
to
make
a
slight
adjustment
in
the
bobbin
tension.
Take
out bobbin
case,
remove
bobbin
and
clean
out
any
dust
or
lint
which
has
collected
around
the
case.
Turn
screw
on
bobbin
case slightly
in
either
direction
using
the
small
screw-driver
(Fig.
24):
To increase
tension
—
turn
screw
slightly
to
the
right
(clockwise).
To
decrease
tension
—
turn
screw
slightly
to
the left
(counter
clockwise)
If
stitch
is
satisfactory
but the
seam
is
puckered,
it
may be
necessary
to
loosen
tension
on
both
top
and
bottom
threads.
An
easy
test
for
checking
tension
balance:
Fold
fabric on
the
bias
and
stitch
(12
stitches/inch)
4”
in
from
fold.
Grasp
stitching
and
pull
with
a
snap
(Fig.
25)
•
if
both
threads
break
(even
though
not
at
tensions
are
balanced.
•
if
upper
thread
breaks
—
loosen
top
tension.
•
if
lower
thread
breaks
—
tighten
top tension.
*
E
Fg
25
CHECKING
TENSIONS
to
make
threads
break.
the
same
place)
—
—16—