2. Move the needle bar up or down as
required; and then tighten the screw.
Figure 9-6.Timing needle with shuttle.
be in proper time for the machine to function
properly. See figure 9-6.
Timing the Needle with the Shuttle
If a class 31 sewing machine does not form
the lockstitch, if it skips stitches, or if it frays or
breaks thread, the needle is not moving in the
proper relationship with the shuttles motion. First
make sure you have the right needle. Check the
needle for the correct class, variety 16 x 87, and
size. Insert the needle in the needle bar (long
groove to the left) as far as it will go (fig. 9-6).
Next compare the needle stroke to the shuttle
stroke. To do this, remove the throat plate. Turn
the balance wheel toward you until the point of
the shuttle on its forward stroke reaches the center
of the needle while the needle is on the upstroke.
At this time, the needle bar should have risen 1/10
inch and the point of the shuttle should be 1/16
inch above the eye of the needle, as shown in A
o f figure 9-6.
NOTE: Prior to making adjustments to the
sewing machine, always follow the
troubleshooting chart in Table 9-1.
If the needle eye is not in this position, the
following steps should be taken:
1. Loosen the needle bar connecting stud
screw, as shown in B of figure 9-6.
3. Rotate the balance wheel through the full
cycle to check the timing.
4. Replace the throat plate.
Timing the Feed Dog with the Needle
The feed driving eccentric is an adjustable
connection between the arm shaft (the shaft in the
head) and the feed rock shaft (first shaft beneath
the bed of the machine). If the feed mechanism
is properly timed, the feed dog should be on its
downstroke and level with the throat plate when
the point of the needle reaches the material. If
there is a twisted knot every 1 to 2 inches on the
bottom of your material, check the timing of the
needle before adjusting the feed mechanism.
To adjust the feed eccentric, first lower the
stitch regulator to the lowest position so the
machine forms its longest stitch. Turn the balance
wheel until the feed dog is on its downstroke and
is flush with the throat plate. Move to the rear
of the machine and take off the arm side cover.
Turn the balance wheel away from you until the
feed eccentric collar setscrew is visible (fig. 9-7).
Hold the collar with your left thumb. Loosen the
screw and rotate the balance wheel away from you
until the needle, on its downstroke, reaches the
material. Tighten the setscrew. Rotate the balance
wheel to check the timing. Recheck the timing of
the shuttle point with the needle. When you time
the feeding mechanism, you may throw the needle
out of time with the shuttle.
Figure 9-7.Feed eccentric.