JUKI MB-373 Manual page 3

Adjustment Procedures
™ Turn the hand wheel by hand and loosen
screw 1 in the Fig. A in the thread take-
up lever to adjust so that the upper
engraved line of the two engraved lines
on the needle bar aligns with the bottom
of lower bushing 3 when the needle bar
is at its lowest position.
For the old type sewing machine, in
addition, adjust the position so that
needle clamp screw 4 enters the slot of
lower bushing 3 as illustrated in Fig. B
when the needle bar is at its highest
position.
Following needles are equipped at the
time of delivery.
MB-373 : Standard needle TQ x 7 #16
MB-377 : Standard needle TQ x 1 #16
MB-377 / Z201 : TQ x 7 #20
MB-377 / Z202 : TQ x 7 #18
1) Adjusting the looper timing
7
™ Loosen two screws 5 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.
2) Clearance between the needle and looper
Loosen two screws 7 in the looper suppot 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.
3) Clearance between the needle guide and needle
Loosen screw 8 in the needle guide and adjust in the
longitudinal position of the needle guide so that the clearance
between needle guide 6 and needle should become 0 to
0.1 mm when the needle bar is at its lowest position.
1
2
3
Fig. B
3
5
3
−
Results of Improper Adjustment
™ If needle bar 2 is too high, skipped
Fig. A
stitches will be produced.
If the needle bar is too low, the
needle will come in contact with the
looper.
4
4
™ 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.
−