JUKI lbh-1790 series Engineer's Manual page 27

Adjustment Procedures
Loosen setscrews 2 in bobbin thread trimming origin detecting
sensor installing plate 1, align the edges of the arrrow mark in
the figure with each other, and tighten setscrews 2.
After assembling the sensor installing plate, check and adjust the
motion referring to "(9) - 1) Bobbin thread trimmer adjustment
mode".
1. Start up 1) Bobbin thread trimmer adjustment mode and set
the trimmer to the waiting position.
2. When bobbin thread trimmer origin is detected, loosen hexagon
screw 1, turn eccentric pin 2, and adjust so that the clearance
between the top end of bobbin thread trimmer 3 and the knife
groove of throat plate is 0 to 1 mm. Then tighten hexagon
screw 1.
3. When the position of eccentric pin 2 is changed, check the
motion and perform the adjustment referring to 1) Bobbin thread
trimmer adjustment mode.
Results of Improper Adjustment
™ When the distance from bobbin
thread trimmer 3 to the knife
groove is large, the trimmer may
not be fully closed.
™ When the distance from bobbin
thread trimmer 3 to the knife
groove is small, the trimmer
comes in contact with the cloth
cutting knife and may be broken
at the time of knife dropping.
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