Singer class 251 - Arm Shaft Replacement

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46
CAUTION:
The
feed
timing
bevel
gears
at
S3
have
been
lapped
to-
gether
at
the
factory
and
should
be kept
in
mesh,
as
instructed
in
Fig.
67,
throughout
the
removal
and
replacement
of
the
arm
shaft.
14.
While
maintaining
position
of
needle
bar
crank,
as
described
in Step 13
on
page
45,
hold
the
blade
of
a
large
screw-
driver
between
the
arm
cast-
ing
and
the
feed
eccentric
U4,
as
shown
in
Fig.
67,
to
keep
the
bevel
gears
in
mesh
and
push
the
end
of
the
arm
shaft
X4,
Fig.
67
into
the
bushing
Z4, Fig.
67.
i~
f7
S3
Fig.
66.
Position
of
Needle
Bar
Crank,
During
Removal
of
Shaft
HOLD
THESE
GEARS
IN
MESH
Fig.
67.
Removing
the
Arm
Shaft
15.
Using
another
shaft,
of
the
same
diameter
as
the
arm
shaft
on
these
machines,
push
the
arm
shaft
X4
further
through
the
ma-
chine
(still
keeping
the
gears
at
S3
in
mesh).
This
temporary
shaft
must
be
pushed
sufficiently
far
into
the
machine
to
hold the entire
gear
and feed eccentric mechanism
in
position
upon
it until
the
arm
shaft
is
replaced.
16.
Finally
grasp
the
needle-bar-crank-end
of
the
arm
shaft
firmly
and
pull
the
arm
shaft
straight
out
of
the
machine.
..
47
TO
REPLACE
THE
ARM
SHAFT
CAUTION: -
Make
certain
that
the
OIL-REMOVING
WICK
ASSEMBLY
is
out
of
the
machine.
1.
Insert
the
machine-pulley-end
of
the
arm
shaft
into
the
arm
shaft
bushing
at
the
head
of
the
machine
arm.
2.
Make
certain
that
the
needle
bar
crank
is
turned
to
the
relative
position
shown
in
Fig.
66
to
clear
the
three
wick
loops
in
holder
W4.
3.
While
still
holding
the
bevel
gears
at
S3
in
mesh,
with
a
screw-
driver,
as
shown
in
Fig.
68,
push
the
arm
shaft
X4
straight
through
the
machine
arm,
the
feed
eccentric
U4
and
the
feed-eccentric-
and-bevel-gear,
X3,
Fig. 68.
(A
light
tapping
with
the
palm
of
the
hand,
against
the
needle
bar
crank
end,
may
be
required.)
<2
A2
y
X3
u\11
\,L _
J,
l
~
f
-:,:1/~
o
s,3
HOLD
THESE
GEARS
IN
MESH
~
~
X4
V4
T4
~
\
R4
Fig.
68.
Replacing
th&
Arm
Shaft
4.
Replace
machine
pulley
so
that
the
two
set
screws
T4
will
lorn!,.
over
the
two
grooves
V4,
Fig.
68
on
the
shaft
and
securely
tighten
set
screw
T4.
5.
Replace
and
tighten
the
arm
shaft
screw
R4
sufficiently
to
remove
all
end
play
of
the
shaft
without binding.
Test
the
arm
shaft
for
freedom
in
rotation.
6.
Move
bevel
gear
X3
toward
machine pulley
and
securely
tighten
feed
timing
screw
Y.
7.
Place
the
first
finger
of
one
hand
on
one
side
of
the
arm
shaft
and
the
first
finger
of
the
other
hand
on
the
other
side
of
the
arm
shaft
so
that
both
fingers
contact
the
bevel
gear
(on
vertical
shaft)
that
mates
with
the
gear
X3.
Feel
for
slight
backlash.
If
there
is
no
backlash,
loosen
timing
screw
Y
and
set
screw
0.
Lightly
tap
gear
X3
away
from
mating
gear
until
there
is
just
a
slight
amount
of
backlash.
Then
<;ecurely
tighten
timing
screw
Y
and
the
set
screws
in
gear
X3.
Recheck
the
backlash.
8.
Using
a
screwdriver,
as
shown
in
Fig. 68,
move
feed
eccentric
U4
as
close
as
possible
to
the
connecting
rod
A2,
Fig.
68
and
tighten
the
timing
screw
and
two
set
screws
in
eccentric
U4.