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WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
Cause (1)
Cause (2)
Checking order and adjusting procedure
9. Triangle double chain looper
thread stitches are skipped.
The needle fails to catch the
double chain looper thread.
One stitch is
skipped.
Viewed from
the wrong
side
9-1)
The needle point is
crushed.
1-A)
The needle point has been crushed and
got thicker and shorter.
Refer to the clause relating to the needle point
crush.
9-2)
Double chain looper
2-A)
The thread hole in the tip has worn, and
the looper thread does not reach the
needle as shown at right.
Replace the double chain looper.
9-3)
Adjustment of looper
3-A)
Excessive returning amount or longitu-
dinal motion will often cause this stitch
skipping.
Refer to the pertinent Standard Adjustment.
9-4)
Thread cam timing
4-A)
The thread cam timing is too early,
causing the looper thread to slack be-
fore the needle enters a thread triangle.
Refer to the pertinent Standard Adjustment.
9-5)
Thread tension
5-A)
The lower thread tension is very low,
and the thread is not stretched.
Increase the thread tension a little.
9-6)
Threading
6-A)
The area around the thread cam has
threaded erroneously.
Correct the threading.
10. Triangle double chain needle
thread stitches are skipped.
The needle fails to catch the
needle thread loop on the
double chain looper, resulting
in the stitch skipping shown
below.
Defectively
interlaced loop
The needle thread
extends to the
adjacent stitch.
10-1) Double chain looper
1-A)
The chain looper is too high and too
close to the throat plate, or has bad
shape.
Correct the height of the chain looper by pushing
it down until it cones into contact with the stopper.
Replace the chain looper having a bad shape.
10-2) Adjustment of looper
2-A)
The returning amount is not enough,
causing the needle to miss the loop.
Refer to the pertinent Standard Adjustment.
10-3) Thread tension
3-A)
The needle thread tension is too low.
Slightly increase the needle thread tension.
10-4) Stitch length
4-A)
The stitch length is as small as 1.5 mm
or less.
Slightly increase the stitch length.
Check whether the position of the thread cam is
too late.
10-5) Needle guard
5-A)
A needle guard is too high, and catches
needle thread loops.
Refer to the pertinent Standard Adjustment.
10-6) Double chainstitch
needle thread guide
6-A)
The needle thread guide is installed too
high, and it fails to tense the thread.
Refer to the pertinent Standard Adjustment.
