Synchronizing Needle And Looper Motions - JUKI UnionSpecial 35800DLU Adjusting Instructions / Illustrated Parts List

SYNCHRONIZING NEEDLE AND LOOPER MOTIONS

NOTE: Needle and looper mechanisms are carefully synchronized with pre-
cision gauges before leaving the factory to insure the best possible sewing
conditions.
Should it become necessary to disassemble the main shaft or replace compo-
nents of the needle or looper drive mechanisms, re-synchronization of the
machine will be required to facilitate proper sewing adjustments. This is accom-
plished by means of an adjustable split coupling located beneath the rear top
cover, connecting the crankshaft to the main shaft, which in turn drives the
looper mechanism.
To synchronize the machine, remove the needles, presser foot, throat plate,
feed dogs and upper feed roller mechanism. Rotate handwheel in the
operating direction until the needle bar is at the bottom of its stroke and just
begins its upward travel. Loosen screw (A, Fig. 2) and remove the looper for the
left hand needle from the looper holder. Insert a straight steel rod (B) 5/32"
(3.9mm) or 11/64" (4.3mm) diameter by 2-1/2" (63.5mm) long into looper holder
and retighten screw (A). Rotate the handwheel until the rod (B) is at the extreme
left and reinstall the throat plate. Loosen screw (F) in looper holder and move
the holder left or right until the right side of the rod is approximaately 5/32"
(4.0mm) from the left edge of the throat plate, tighten screw (F). Turn the
handwheel in the operating direction, with needle bar rising until rod (B) comes
in contact with the edge of the throat plate. At this point, clamp Union Special
timing gauge No. TT147 (C) around the needle bar (D), flush against the
underside of the machine casting (E). Rotate handwheel in the opposite
direction until either the gauge contacts the machine casting on the up stroke
of the needle bar or the rod contacts the edge of the throat plate. Maximum
allowable clearance between gauge and casting or rod and throat plate is
.005" (0.1mm)
FIG. 2
If machine is not synchronized the following applies:
Both ends of the adjustable split coupling are secured to the crankshaft and
C
main shaft by spot screws and set screws. On the main shaft end of the coupling
(A, Fig. 3) three screws (B) thread horizontally through the coupling. The holes
in the main shaft end of the coupling are larger than the diameter of the screws,
permitting several degrees of rotation in either direction to properly synchronize
the needle and looper. Loosen the three horizontal clamp screws (B, Fig. 3).
With rod (B, Fig. 2) at its farthest position to the left, snug the uppermost horizontal
clamp screw enough to hold coupling (A, Fig. 3) in position. If the handwheel
A
B
is turned in reverse of operating direction and gauge (C, Fig. 2) on needle bar
(D) contacts the machine casting (E) before rod (B) contacts the edge of the
throat plate, loosen horizontal clamp screw (B, Fig. 3) which was snug, while
holding the coupling in place with an Allen wrench in set screw (C). Rotate the
handwheel slightly in reverse of operating direction, snug the uppermost
horizontal clamp screw (B), recheck synchronization. If the handwheel is turned
in reverse of operating direction and the rod contacts the edge of the throat
plate before the clamp gauge contacts the machine casting, adjust as before,
except turn the handwheel slightly in the operating direction. Use shim stock to
FIG. 3
insure no more than .005" (0.1mm) exists between gauge and casting or
between rod and throat plate, in both the operating and reverse directions of
the handwheel. When this setting has been made, tighten the three horizontal
clamp screws (B, Fig. 3) securely, and recheck both clearance points with .005"
(0.1mm) shim gauge to assure no slippage occurred while tightening the
screws.
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