JUKI lbh-1790 series Engineer's Manual page 17

Adjustment Procedures
1. If needle thread trimmer 2 fails to provide consistent thread
grasping force, loosen setscrew 1 and remove needle thread
trimmer 2.
2. Slightly bend the top end of thread presser spring 3 by hand
so that it comes in contact with thread trimming blade of upper
knife 4 over the length with no clrarance and so that the needle
thread trimmer securely holds the thread regardless of the
position of the thread trimming blade at which the thread is
trimmed.
1. Loosen setscrew 1 in the needle thread trimmer and move
the trimmer up or down to adjust the height. Set the clearance
between the trimmer and the presser as low as possible,
provided that they do not come in contact with each other, in
order to minimize the length of remaining thread on the needle
after trimming.
2. Note that the presser tilts when sewing a multi-layered portion
of the material. Slightly raise the installing position of the trimmer
so that the presser does not come in contact with the trimmer.
Results of Improper Adjustment
™ When the thread grasping force
of needle thread trimmer 2 is
low, slip-off of needle thread at
the start of sewing or thread
grasping failure after thread
trimming occurs.
™ W h e n t h e t r i m m e r i s s e t
excessively high, trimmer open
lever 2 comes in contact with
needle thread trimmer lower
knife pin 3 when trimmer open
lever 2 is actuated, and
malfunction may occur. In this
case, loosen setscrew 4 and
raise upward the height of
trimmer open lever 2 to prevent
the contact.
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