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o Excessive return of the lower
looper tends to cause stitch
skipping when filament thread is
used.
o Insufficient return of the lower
lopper tends to cause needle
thread stitch skipping when spun
thread is used.
o Excessive clearance will often
cause needle thread stitch
skipping.
o Insufficient clearance will cause
needle breakage due to the con-
tact of the looper with the needle,
or produce scratches on the
blade point of the looper, lead-
ing to needle thread breakage or
other troubles.
1) Returning amount of the lower looper
1
Loosen setscrew of lower looper support arm and adjust lower
looper to make adjustment of the returning amount.
(Referential information)
1. Radius
K
of lower looper will be 66.9 mm when the lower
looper is inserted into lower looper support arm until it con-
tacts with stopper pin and then is fixed.
2. The rocking angle of the lower looper will be 26°.
2) Clearance between the lower looper and the needle
1
Loosen setscrew of lower looper support arm to the extent that
it is temporarily tightened. Then finely adjust the longitudinal position
of the looper using fine adjustment screw .
2
Turn fine adjustment screw clockwise to move lower looper away
from the needle.
Turn the screw counterclockwise to move lower looper closer to it.
Adjustment Procedure Results of Improper Adjustment
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