NOTE: Rotate the eccentric no more than
about 1/16 inch, then tighten its setscrews
and check for results.
Timing the Movement of
the Needle Bar Frame
Set the zigzag knob for straight stitch. Turn
the handwheel and observe the travel of the needle
into and out of the needle slot in the throat
(needle) plate. If the needle is not centered in the
slot, make the adjustments that have been
described.
Now adjust the needle to produce the widest
zigzag stitch. Turn the handwheel toward you and
observe vibration (sidewise movement) of the
needle bar. The needle bar, on its upward
movement, should begin to vibrate when the point
of the needle is no less than about 3/32 inch above
the throat plate, and should stop vibrating when
the needle has reached approximately the same
position on its downward movement. To adjust
the vibration of the needle bar on model 99R,
loosen the setscrews (H of figure 9-51) in the
vibrator cam and slightly turn this cam on its
shaft. Tighten the setscrews and check for results.
On model 99R-3, the vibration of the needle
bar is produced by a plate cam located at R on
figure 9-51. Loosen its setscrews and slightly turn
the cam on its shaft, following the same procedure
as outlined in the preceding paragraph. Be sure
to retighten the setscrews.
To Raise or Lower the Feed Dog
When at its highest position, the feed dog
should usually rise above the throat (needle) plate
the full depth of the teeth.
To adjust the position of the feed dog, loosen
screw (J of fig. 9-50) and raise or lower the feed
dog; then tighten the screw. When raising or
lowering the feed dog, be careful that its underside
does not drop so low that it strikes the hook.
239.461
Figure 9-52.—Adjusting thread take-up spring.
Adjustment of the Thread Take-up Spring
The thread take-up spring (K of fig. 9-52)
should be set so that when the eye of the needle
reaches the material on the downward stroke, the
spring has completed its action and rests against
the top of the thread take-up spring regulator.
If the thread take-up spring is not correct,
loosen setscrew (L of fig. 9-52) and turn the
tension stud (M) to the left for reduced movement
of the spring, or to the right for more movement.
After the take-up spring is set correctly, tighten
setscrew (L).
Regulation of the tension of the thread take-
up spring (K) is done by turning the tension stud
(M) to the right to increase tension or to the left
to decrease it. Tension of the spring should just
be enough to take up the slack of the needle thread
until the eye of the needle reaches the material
on its downward movement.
9-39
