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48
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Troubles
Cause (1)
Cause (2)
Checking orders and corrective measures
6
.
Needle thread is not trimmed. (Bobbin
thread is trimmed.)
7
.
Bobbin thread is not trimmed. (Needle
thread is trimmed.)
8.
Wiper comes in contact with needle.
9.
Moving knife breaks.
Stitch skipping at the last stitch
Sharpness of a part of blade of knife is
defective.
Amount of recession of moving knife is
short.
Position of bobbin thread when trimming
thread is not stable.
Height of installation of wiper is improper.
Defective timing of the respective sections
Needle thread is tensed when trimming
thread.
Attaching of needle is improper.
Stroke of thread take-up spring is too large.
Hook adjusting is improper.
Blade sections of moving knife and counter
knife do not engage closely with each other
when trimming thread.
(Installing angle, position, and tilt of blade
top face of the counter knife are not
adjusted to the blade section of the moving
knife.)
Adjustment of amount of recession of the
moving knife is improper.(Lateral position
of knife actuating shaft and lateral position
of thread trimmer cam are improper.)
Hook other than specified is used.
Thread trimming timing is improper.
Upper stop position is improper.
Thread tension disk does not rise when
trimming thread.
Hangnail of thread
Properly attach the needle. Check whether the needle is bent.
Decrease the stroke of thread take-up spring.
Check stitch skipping by operating the machine at low speed.
Readjust the hook.
(Advance the hook timing.)
Remove throat plate, move the knife by hand, and cut
approximately three pieces of cotton thread #50.
The knife is good if the three threads can be cut equally. If not,
sharpen the blade of counter knife, correct tilting angle at the top
end, or readjust the installing position of counter knife.
Check the amount of recession of moving knife, and adjust the
lateral position of thread trimmer cam so that the amount of
recession of moving knife is 2.5 to 3 mm.
Check whether there is the bobbin thread guide groove on the
hook. If not, replace the hook with one for thread trimmer.
Readjust the installation of wiper.
Adjust the timing referring to the item (3-5).
Adjust the position referring to the item (3-1).
Adjust the timing of disk rising with the thread tension setscrew.
Loosen thread tension release wire presser (lower) and readjust
the position of wire.
Check whether the top end of needle is blunt. Replace the needle,
or use the ball-point needle.
Check hook timing or the clearance.
Check scratches on hook blade point or other thread paths, and
correct them with buff or the like.
Use optimum gauges or needle for the thread thickness.
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