Singer Centurion 121D User manual

SINGER
121D,121C

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
Form 21624 (Rev 977)
I UAL
I *
Sewing l\llachine
121D CLASS
121C CLASS
Copyright ' 1976 The Singer Company
All Rights Reserved Throughout the World
•A Trademark of THE SINGER COMPANY
Printed in U.S.A.

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
LUBRICATION
Moving
parts
have
either
permanently
sealed
pre-lubricated
ball
or
needle bearings
or
oil
impregnated
bushings
which
require
no manual
lubrication.
The
following
exceptions
are:
HOOK
An oil
reservoir
supplies
oil to the
sewing
hook race and is
filled
through the oil
cup
as
shown,
with
Singer
Type
"C"
oil,
until
the word
"MAX"
is seen in the
indicator
window.
Check
oil level at
indicator
window
daily
before
starting
machine. As oil level decreases,
red
arrow
will
appear
(Fig. A).
-------------------------------
0
FIG. A
1

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,.
TO TEST HOOK LUBRICATION
Thread
machine
and
sew
3
yards
of
scrap
material.
Pay
no
attention
to
stitch
quality
or
amount
of
oil
at
this
time.
Remove
material
and
bed
slide.
Run
machine
approximately
one
minute
to
establish
a
uniform
oil
flow.
Without
stopping
machine,
hold
a
piece
of
paper
in
place
under
hook
for
10
seconds.
Remove
paper
and
compare
oil
pattern
with
Fig. B
for
proper
oil
flow.
•,
..
·,'
....
...
. .
..
.
.
. . .
.
•
•-I,
FIG. B
If
there
is
no
trace
of
oil
or
an
excess,
adjustment
should
be
made
with
the oil
metering
screw.
In
order
to
gain
access
to oil
metering
screw,
the
hook
should
be
in
position
as
shown
in Fig.
C.
Turn
oil
metering
screw
clockwise
for
more
oil
and
counterclockwise
for
less
(Fig. D).
Normal
setting
is
made
by
turning
the
metering
screw
all
the
way
in
and
then
backing
the
screw
3
or
4
turns
out.
More
or
less
turns
may
be
required
depending
on
the
operation
being
performed.
Oil
Metering
Screw
Oil
Metering
Screw
More
Oil Less Oil
FIG. C FIG. D
2

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If oil flow is not satisfactory, remove hook
assembly
and oil filter.
Check
filter. Oil
wick
should
be replaced
whenever
it has
become
clogged with
lint
or dirt.
An
excess
of oil
sometimes
indicates
that the
filter
wick
has become
detached
from the
screw
or the
screw
is not
securely
tightened.
Inspect
all oil passages to see they have not become
clogged.
011
Filter~
...
:·/•/•'
---
Wick
Hook Assembly
3

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l .
'
MACHINE
THREADING
1.
Move
take-up
eyelet
to
its
highest
point.
2.
Lead
thread
from
thread
stand
through
thread
post
atop
machine
arm
3.
Through
3
eyelets
of
thread
guard
4.
Units
with
U.T.T.,
through
pretensioner
5.
Down
through
thread
retainer
6.
Into
and
around
tension
assembly
7.
Over
check
spring
and
under
slack
thread
regulator
8.
Up
to
and
through
thread
retainer
and
take-up
eyelet
9.
Down
through
thread
retainers
(2)
10.
Through
needle
bar
thread
guide
11.
Through
needle
eye
from
left
to
right
ioner
,,
For
Units
with
I!
Underbed
Thread
Trimmer
,,
I'
1:
i,
I
4

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STITCH
LENGTH
The
stitch
length
can
be
regulated
while
the
machine
is in
operation
To
obtain
the
desired
stitch
length
in
forward
feed,
turn
regulating
thumb
screw
on oil
pan
"in"
(coun-
terclockwise)
for
less
stitches
per
inch,
and
"out''
(clockwise)
for
more (Fig.
A)
To
adjust
the
stitch
length
for
reverse
feed, it is
necessary
that
the
reverse
stopping
block
be
properly
positioned
This
is
done
by
loosening
the
lock
screw
in the
stopping
block
and
sliding
the
slide
block
up
or
down
to the
desired
stitch
length
The
locking
screw
must
then
be
retightened
(Fig.
B)
Regulating
Thumb
Screw
--~'.
More
Less
FIG. A
Stitch
Length/
,,~'
0
1
~'t.-~
Regulating
Screw
IRB,,
i!tit•J
•I
FIG. B
FIG. C
PREVENTING
UNAUTHORIZED
CHANGES
IN
STITCH
LENGTH
To
prevent
unauthorized
changes
in
stitch
length
remove
the
retainer
plate
screw
and
take
out
the
retainer
plate
spacer.
Replace
and
tighten
the
retainer
plate
screw
(without
spacer)
which
will
lock
the
retainer
plate
against
the
stitch
regulating
gears
(Fig. C)
ADJUSTABLE
STITCH
LENGTH
STOP
An
adjustable
stitch
length
stop
is
provided
to
prevent
the
machine
from
making
stitches
longer
than
pre-determined
maximum.
To
adjust
the
stop,
set
the
machine
to
desired
stitch
length
as
previously
instructed
and
turn
stop
screw
until
it
bottoms
against
the
stitch
length
regulating
screw
Lock
stop
screw
in
place
with
stop
screw
nut
(Fig.
C)
Stitch
length
setting
should
NEVER
EXCEED
capacity
of
fittings
in use.
5

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PRESSER
FOOT
PRESSURE
The
pressure
on
the
material
should
be
as
light
as
possible
while
still
sufficient
to.ensure
correct
feeding
There
are
two
regulating
screws
that
control
the
presser
foot
pressure
One
atop
the
arm
and
one
at
the
rear
of
the
machine
The
one
atop
the
arm
is
the
major
control,
normally
adjusted
prior
to
long
production
runs
or
new
applications
For
day-by-
day
casual
adjustments,
the
regulating
screw
al
the
rear
is
used.
screwing
in
for
less
pressure
and
unscrewing
for
more
pressure
When
this
rear
screw
1s
unscrewed
all
the
way
out,
it
disengages,
only
then
can
the top
screw
be
applied.
and
it
serves
as
the
sole
control
until
the
rear
screw
1s
again
turned
inward
(Fig
A)
Regulating
Screw
B when
c.---c
Screw
A
is
Disengaged -
:::=::
Regulating
Screw
A
0 0
0
FIG. A
6

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HOOK TIMING
Proper clearance between needle and hook point, re-
quires that the point of the hook should pass the nee-
dle as closely as possible without striking or deflect-
ing it. There should be .003" - .005" clearance bet-
ween the two (Fig. A).
To
adjust clearance, loosen bushing set screw (Fig.
B).
With screwdriver placed as shown move entire
hook and bushing (Fig. C). Tighten bushing set
screw.
Hook Bushing
Set Screw
FIG. B
Insure that the needle guard prevents the
needle from
contacting the hook point at
any time. If large needles are to be used it
may be
necessary to string the needle
guard back to allow hook point closer to
needle (Fig. D).
7
FIG. C
Needle Guard
FIG. D
.003 - .005
Flat of
Hook Point
To Needle
FIG. A

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HOOK TIMING CONT'D
Reset position finger so there is .018" -
.022" thread clearance between finger and
basket (Fig. E).
FIG. E
For 200 Variety Machines (.085" Loop Rise)
Loosen hook set screws. Turn hand wheel in direction of rotation until needle bar is on
the rise stroke and the lowest mark is aligned with the needle bar height indicator Set
hook point to the centerline of the needle (Fig. F) Tighten hook set screws.
FIG. F
Hook Point to
Centerline of Needle
For 300 Variety Machines (.100" Loop Rise)
Loosen hook set screws. Turn hand wheel in direction of rotation until needle bar is on
the rise stroke and the center mark is aligned with the needle bar height indicator. Set
hook point to the centerline of the needle (Fig. F) Tighten hook set screws
8