o TROUBLES
AND
CORRECTIVE MEASURES
Trouble
Cause
Corrective measures
A.
Thread breakage.
1.
Thread
is
ravelling
{1)
There are scratches
on
the o
Make
those surfaces smooth by
or worn
out
surface
of
thread paths,
on
the
making use
of
a fine sand-paper
pointed end
of
the needle, on the for the hook
point
or a buff for
hook point or on the rear groove the throat plate groove.
of
the throat plate
to
positioning
the bobbin case holder.
(2) Needle thread tension
is
too
o Refer
to
111-7.
high.
"Adjusting the thread tension".
(3) Bobbin case opening mecha-
o Loosen the set screw on the
nism actuates too much. bobbin case opening mechanism
and bring it closer
to
the sewing
hook. (see IV-2).
(4) Needle contacts with the o Tap the hook driving shaft
sewing hook.
saddle gently to adjust the clear-
ance between the needle and the
blade point
of
sewing hook.
(see IV-4)
(5) Lubricating oil fed
to
the
o Adjust the amount
of
oil fed to
sewing hook
is
too short.
the sewing hook. (see III-2).
2.
Needle thread
is
{1)
Needle thread tension
is
too
o Synthetic fiber thread
is
affected
snapped remain-
low.
significantly. Suitable needle
ing a length
of
2
thread tension is
20g. and bobbin
to
3cm (about
thread tension
is
15g. in the case
1") on the bot-
of Synthetic fiber thread.
tom
surface
of
(see III-7).
sewing material.
(2) Thread take-up spring has
o Decrease the tension and increase
high tension and small stroke.
the stroke
of
thread take-up
spring. (see
111-7-(3)).
(3)
Needles are attached incor- o The cross-section view of 2
rectly.
needle eyes
as
viewed from their
(especially synthetic fiber thread top.
is
used.)
a.
Not good for synthetic fiber
thread.
~
~
b.
Standard.
~
§
c.
In some cases good for synthe-
tic fiber thread.
@
@
-
19-
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