Problem
The lower thread
breaks.
Skipped stitches
occur.
Skipped stitches
occur at the sewing
start.
The upper thread
does not tighten.
The
lower thread
does not tighten.
The seam is
puckered.
1--
~--------P_o_s_s_ib_l_e_c_a_u_se
________
~ll
~
____________
R_e_m_e_d_v
____________
~I_P_as_e~~
r-
y
The lower thread tension is too strong.
The bobbin is not turning
smoothly.
Too much thread is wound around the bob-
bin.
The
needle is installed incorrectly.
The
needle is bent,
or
the needle tip is
broken.
The
needle
size
is incorrect
The presser foot pressure is too weak.
The bobbin is spinning and the
length
of
the lower thread coming
out
of
the bobbin
case
is too short to
be
pulled up during
thread trimming.
The amount
of
upper thread remaining at
the
needle is too short.
• The upper thread tension
is
too weak.
• The lower thread tension is too strong.
• The upper thread tension is too strong.
• The lower thread tension is too weak.
The upper
and
lower thread tensions are
too
s~rong.
The presser foot pressure
is
too strong.
The
needle tip is broken.
The
needle
is
too thick.
-45-
-
Decrease the thread tension.
Replace the bobbin or the bobbin
case.
Do
not wind 6n more than
80%
of
the bob-
bin capacity.
Install the needle correctly.
Replace the needle.
Use a needle that is suitable for the thread.
Increase the presser foot pressure.
Replace
the
bobbin winding prevention
spring.
Adjust the pretension.
Adjust the thread tension.
Adjust the thread tension.
Loosen the upper and
lower thread ten-
sions.
Decrease the presser foot pressure.
Replace the needle.
Use
as
thin a needle
as
possible.
~
27
B737MKm (English)
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