–
39
–
24. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Troubles
Causes
Corrective measures
1. Thread breakage
(Thread frays or
worn out.)
(Needle
thread
trails 2 to 3 cm
from the wrong
side of the fabric.)
1
Thread path, needle point, hook blade
point or bobbin case resting groove
on the throat plate has sharp edges or
burrs.
2
Needle thread tension is too high.
3
Bobbin case opening lever provides an
excessive clearance at the bobbin case.
4
Needle comes in contact with the blade
point of hook.
5
Amount of oil in the hook is too small.
6
Needle thread tension is too low.
7
Thread take-up spring works excessively
or the stroke of the spring is too small.
8
Timing between the needle and the hook
is excessively advanced or retarded.
™
Remove the sharp edges or burrs on the
blade point of hook using a
fi
ne emery paper.
Buff up the bobbin case resting groove on
the throat plate.
™
Decrease the needle thread tension.
™
Decrease the clearance provided between
the bobbin case opening lever and the bob-
bin. Refer to “21. ADJUSTING THE BOBBIN
CASE OPENING LEVER.”
™
Refer to “18. NEEDLE-TO-HOOK RELA-
TION.”
™
Apply oil to the surface of the lace of the
hook. (See “6. LUBRICATION.”)
™
Increase the needle thread tension.
™
Decrease the tension of the spring and in-
crease the stroke of the spring.
™
Refer to “18. NEEDLE-TO-HOOK RELA-
TION.”
2. Stitch skipping
1
Timing between the needle and the hook
is excessively advanced or retarded.
2
Pressure of the presser foot is too low.
3
The clearance provided between the top
end of the needle eyelet and the blade
point of hook is not correct.
4
Hook needle guard is not functional.
5
Improper type of needle is used.
™
Refer to “18. NEEDLE-TO-HOOK RELA-
TION.”
™
Tighten the presser spring regulator.
™
Refer to “18. NEEDLE-TO-HOOK RELA-
TION.”
™
Refer to “19. ADJUSTING THE HOOK
NEEDLE GUARD.”
™
Replace the needle with one which is thicker
than the current needle by one count.
3. Loose stitches
1
Bobbin thread does not pass through the
tension spring of the bobbin case.
2
Thread path has been poorly
fi
nished.
3
Bobbin fails to move smoothly.
4
Bobbin case opening lever provides too
much clearance at the bobbin.
5
Bobbin thread tension is too low.
6
Bobbin has been wound too tightly.
™
Thread the bobbin case correctly.
™
Remove rough parts with a
fi
ne emery paper
or buff it up.
™
Replace the bobbin or hook with a new one.
™
Refer to “21. ADJUSTING THE BOBBIN
CASE OPENING LEVER.”
™
Increase the bobbin thread tension.
™
Decrease the tension applied to the bobbin
winder.
Summary of Contents for PLC-1690
Page 2: ......
Page 3: ...i DEUTSCH 3 3 3 I II...
Page 4: ...ii 1 5 1 2 3 4 1 2 3 1 2 1 1 2 2 1 2 2 2 3 3 4 5...
Page 5: ...iii DEUTSCH 1 2 3 1 2 I 1 2 II 1 V 30mm 2 3 III 1 2 IV 1 2 V 1 2 3 1 2 3 4 5 V...
Page 6: ...iv 6 7 1 JUKI JUKI 2 3 1 2 3 4 5 6 7 8 9 1 2 10 3 4 5 35 35 85 5 6 7 8 85dB 90dB 90dB 9...
Page 7: ...v 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9...
Page 13: ...xi...
Page 34: ...xxxii...
Page 35: ...xxxiii...
Page 36: ...xxxiv 9 PP 9 9...
Page 37: ...xxxv 8 8 f...
Page 38: ...xxxvi 1 2 3 V 4 V 5 6 1 2 3 4 5 6 7 8 9...
Page 80: ...38 24 1 2 3 cm 1 2 3 4 5 6 7 8 21 18 6 18 2 1 2 3 4 5 18 18 19 1 3 1 2 3 4 5 6 21...
Page 86: ...44 24 KU 1 2 3 4 5 6 7 8 1 2 3 4 5 1 2 3 4 5 6...
Page 87: ......
