28.
Conversion
to
Another
Subclass
To convert
the
machine to
another
subclass, remove presser foot, needle plate and feed dog,
tilt
the
machine
back
and
strip
the
vibrating presser.
Relieve
the
pressure
of
the
presser
bar
spring
by
turning
out
pressure
regulating
screw
19
(Fig.
19).
Before you install a new vibrating presser,
check
to
see
that
the mounting surfaces on
the
bracket
and
on
the
vibrating
presser
are
clean.
Loosen binding screw K (Fig. 40) on the driving lever and check to make sure the vibrating
presser
works
smoothly.
The
guide
should
have
a
vertical
clearance
of
.004",
or 0.1
mm,
maximum.
Worn
connections
should
be replaced by new ones. As you replace the feed dog
and
the
needle
plate, make
sure
the
former
moves
freely in
the
feed
slots.
After all the parts replaced have
been
adjusted
correctly, reset
the
presser foot pressure.
29.
Setting
the
Feed
Dog
at
Correct
Height
To facilitate this adjustment, it is recommended to use all-purpose gauge No. 91-129 604-01
which is pushed over the feed slot so that its
edges
are in line with the
edges
of the needle
plate. This
gauge
is held in place by the presser foot (Fig. 35). If
the
feed
dog
has
been
set
correctly, all its teeth should contact the bottom of the recess on the underside of the gauge
when
the
feed
dog
is at its
highest
point.
Prerequisite
for
setting
the
feed
dog
at
the
correct
height
is
that
its
motion
has
been
timed
correctly, as
instructed
in
Chapter
35.
To
set
the
feed
dog
at
the
correct
height,
proceed
as
follows:
Fig.
35
R
9534
38
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