JUKI LH-4128-7, Engineer'S Manual

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1. Remove the throat plate bobbin case opening lever, feed dog and
needle.
2. Loosen three screws which are used to secure the hook driving shaft
gear.
3. For the sewing machine equipped with a thread trimmer, remove the
counter knife.
4. Draw out the hook upwards.
5. Replace the thrust plate and spacer of the hook driving shaft upper
bushing with appropriate ones.
* Thrust plate and spacer of the hook driving shaft upper bushing are
prepared respectively the sewing machine with/without a thread
trimmer.
(Caution) 1. For this type of sewing machine, the bottom section of
the hook shaft is sealed with gaskets. Therefore, if any
air pressure is exerted, loosen the bottom screws (4
pcs.) used to fix the hook shaft base from the bottom.
Then, tighten the setscrews (3 pcs.) of the hook shaft
screw gear under the condition of no air pressure.
If the clearance provided between
the throat plate and the bobbin case
stopper is larger than the specified
value:
o The bobbin case may come off
the throat plate.
If the clearance provided between
the throat plate and the bobbin case
stopper is smaller than the specified
value:
o Isolated idling loops will result.
o Moving knife will come in contact
with the hook at the time of
thread trimming.
Adjustment Procedure
Results of Improper Adjustment