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2. trouBLE SHootING
Phenomenon
. Thread
1 The thread path, tp of needle, blade pont
breakage
of hook, or bobbin case positioning finger
has scratches.
2 The needle thread tenson s too hgh.
3 The needle comes n contact wth the
blade pont of hook.
4 Lubrcatng ol n the hook s too small.
5 The needle thread tenson s too low.
6 The thread take-up sprng pressdre s too
hgh, and stroke of the thread take-up le-
ver s too small.
7 The tmng between needle and hook s
too early or too late.
8 Idlng amount of the bobbn s too large.
2. Sttch skp-
1 The clearance between the needle and
png
the hook pont s too large.
2 The tmng between the neede and the
hook s too early or too late.
3 The holder pressure s too low.
4 The clearance between the top edge of
the needle eyelet and the hook pont s
not correct.
5 The needle thread gude s not properly
threaded.
e Refer to
dle thread"
3. Loose
1 The thread has not been passed through
sttches
the forked secton of the bobbn case ten-
son sprng.
2 The thread path has been poorly finished.
3 The bobbn does not rotate smoothly.
4 The bobbn thread tenson s too low.
5 The bobbn thread tenson s too hgh.
6 The presser sponge s located too close
to the needle entry. As a result, the thread
comes n contact wth the sponge. e Cut
the secton of sponge whch comes n
contact wth the thread.
cause
"!-4-2. threading the nee-
p.14.
6
－
－
corrective measure
○ Re-sharpen the blade pont of hook wth
a fine emery paper to remove scratches.
Buff the bobbin case positioning finger.
○ Adjust the needle thread tenson.
○ Refer to
"#-1-2. Needle and hook ad-
justment"
p.109.
○ Adjust the ol amount properly. Refer to
"#-1-7. Hook oil amount (track of oil)
adjustment" p.112
and
ing the oil amount in the face plate"
p.113.
○ Adjust the needle thread tenson prop-
erly.
○ Decrease the pressure of the thread
take-up sprng, and ncrease the stroke
of thread take-up lever.
"#-1-2. Needle and hook ad-
○ Refer to
justment"
p.109.
○ Increase the sprng pressure.
"#-1-2. Needle and hook ad-
○ Refer to
justment"
p.109.
"#-1-2. Needle and hook ad-
○ Refer to
justment"
p.109.
○ Tghten the holder sprng regulator.
"#-1-2. Needle and hook ad-
○ Refer to
justment"
p.109.
○ Properly thread the bobbn case.
○ Grind the thread path with a fine emery
paper, or buff t up.
○ Replace the bobbn or the hook.
○ Adjust the bobbn thread tenson prop-
erly.
○ Decrease the bobbn thread tenson.
"#-1-8. adjust-
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