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24. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Troubles
1, Thread breakage
(Thread frays or is worn
out.)
(Needle thread trails 2 to
3 cm from the wrong
side of the fabric.)
2, Stitch skipping
3, Loose stitches
Causes
(\) Thread path, needle point, hook blade
point or bobbin case resting groove on
the throat plate has sharp edges or burrs.
Needle thread tension is too high.
Needle comes in contact with the blade
point of hook,
@:; Amount of oil in the hook is too small.
Needle thread tension is too low.
@ Thread take·up spring works excessively
or the stroke of the spring is too small.
iJ) Timing between the needle and the hook
is excessively advanced or retarded,
Q) Timing between the needle and the hook
is excessively advanced or retarded.
(2) Pressure of the presser foot is too low.
Q) The clearance provided between the top
end o! the needle eyelet and the blade
point of hook is not correct
@ Improper type of needle is used.
Bobbin thread does not pass through the
tension spring of the bobbin case.
(J) Thread path has been poorly finished.
CT) Bobbin fails to move smoothly.
@) Bobbin thread tension is loo low.
®
Bobbin has been wound loo tightly,
@ Needle tip is worn out
i
Corrective measures
I
o Remove the sharp edges or burrs on the
blade point of hook using a fine emery
paper. Buff up the bobbin case resting
groove on the throat plate.
o Decrease the needle thread tension.
o Refer to "17. NEEDLE,TO•HOOK
RELATION."
o Adjust the amount of oil in the hook
properly.
Refer to "5. LUBRICATION",
o Increase the needle thread tension.
o Decrease !he tension of the spring and
increase the stroke of !he spring,
o Refer to "17.
NEEDLE-TO·HOOK
RELATION."
o Refer to "17, NEEDLE•TO•HOOK
RELATION."
o Tighten the presser spring regulator,
o Reier to "17,
NEEDLE·TO·HOOK
RELATION."
o Replace the needle with one which is
thicker than the current needle by one
count
o Reier to "7. THREADING THE BOBBIN
THREAD",
o Remove rough parts with a line emery
paper or buff ii up.
o Replace !he bobbin or hook with a new
one.
o Increase the bobbin thread tension.
o Decrease the tension applied to the
bobbin winder.
o Replace the needle.
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