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4-9-3. Checking of the knife unit
WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the
sewing machine.
❶
Standby state of the knife
A
5 to 6 mm
❶
❶
Aligning state of salient portion of loop spreading
knife and thread trimming knife
Far end of the hole in
loop spreading knife
❶ aligns with the tip of
thread trimming knife
❷
❶
2 to 2.5 mm
(H type : 2.5 to 3 mm)
State of engagement of knife
❷
❷
❷
❶
❷
A
❷
A
– 22 –
1) Check to make sure that the power switch is in
the OFF state. Remove the gauge (presser foot,
throat plate and feed dog) from around the nee-
dle.
2) In the standby state of loop spreading knife ❶ ,
the distance from center of needle A to the tip of
loop spreading knife ❶ is 5 to 6 mm.
Be aware that, if the distance between
loop spreading knife ❶ and center of
needle A is reduced, thread loop is likely
to interfere with loop spreading knife ❶ .
* Refer to
"4-9-4. Adjustment of the knife unit" p.
23
for how to adjust it.
3) The purpose of adjustment of the aligning position
of loop spreading knife ❶ and thread trimming
knife ❷ (far end of the hole in loop spreading
knife ❶ and the tip of thread trimming knife ❷ ) is
to align the aforementioned aligning position with
center of needle A.
Be aware that, if the aligning position of
the loop spreading knife and the thread
trimming knife does not align with
center of needle A, the length of thread
remaining on the material after thread
trimming will be longer.
4) The amount of engagement between loop spread-
ing knife ❶ and thread trimming knife ❷ is 2 to
2.5 mm (H type : 2.5 to 3 mm) as measured from
center of needle A.
Be aware that, if the amount of
engagement between them is
insufficient, faulty thread trimming can
occur.
"4-9-4. Adjustment of the knife unit" p.
* Refer to
23
for how to adjust it.
In the case of using a thread that is
likely to cause unstable thread loop
formation, the needle thread may be
trimmed extremely short when thread
trimming is carried out at a position
where no material is present.
In this case, correct the aforementioned
problem by increasing the thread take-
up spring stroke to a value that is larger
than the standard value.
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