JUKI MB-1800 Engineer's Manual page 10

Adjustment Procedures
1) Slightly loosen knob 1 and turn cover 2 in the direction
of the arrow and you will find hand pulley 3.
2) Turn the hand pulley by hand, loosen setscrew 4 in the
needle bar thread-take up lever and adjust so that the
upper engraved line of the two engraved lines on the
needle bar aligns with the bottom of the lower bushing
when the needle bar is at its lowest position.
1) Adjusting the looper timing
™ Loosen the two screws 3 in the looper and cam sleeve
and adjust in the rotating direction of the looper and
cam sleeve so that the looper's blade point aligns with
the center of the needle when the lower engraved line
of the needle bar is aligned with the bottom of the lower
bushing. Then tighten the screws 3.
2) Clearance between the needle and looper
Loosen two screws 4 in the looper support ring and adjust
in the longitudinal position of the looper when the looper's
blade point is aligned with the center of the needle. Then
tighten the screws 4.
3) Clearance between the needle guide and needle
Loosen the screw 2 in the needle guide 1 and adjust in
the longitudinal position of the needle guide 1 so that the
clearance between the needle guide 1 and needle should
become 0.05 to 0.1 mm when the needle bar is at its lowest
position. Then tighten the screw 2.
Results of Improper Adjustment
™ If the needle bar is too high, skipped
stitches will be produced.
If the needle bar is too low, the needle
will come in contact with the looper.
™ If the clearance between the needle
and looper is too excessive, it is likely
to produce skipped stitches. If the
clearance is too small, in accordance
with the material used, the needle will
come in contact with the looper
resulting in needle breakage and
looper's blade point breakage.
™ For thick materials and overlapped
sections, adjust the clearance between
the needle guide and needle so that
the needle guide touches the needle
by 0.1 to 0.2 mm.
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