Singer 251 User manual

SINGER
CLASS 251

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2
USE
SINGER*
OILS
and
LUBRICANTS
They
insure
freedom
from
lubricating trouble and give
longer life
to
sewing equipment
The
following are
the
correct lubricants
for
the
241,251,253,
400w,
402w
and
4/0w
Machines:
TYPE
A -MANUFACTURING MACHINE
OIL,
LIGHT
GRADE
When
an
oil
is
desired
which will produce
a
minimum
of
stain on fabrics,
even
alter
a
long period
ol
storage, use:
TYPE
C -MANUFACTURING MACHINE
OIL,
LIGHT
GRADE
OTHER
SINGER
LUBRICANTS
TYPE
E -
THREAD LUBRICANT
For
lubricating
the
needle
thread
of
sewing
machines
for
stitching
fabrics
or
leather
where
a
thread
lubricant
is
required.
TYPE
F -MOTOR OIL
For
oil
lubricated
motors
and
plain
bearings
in
rower
tables
and
transmitters.
NOTE: All
of
the
above
oils
are
available
in
quart,
1 gallon and
5
gallon
cans.
BALL BEARING LUBRICANT
This
pure
grease
is
specially
designed
for
the
lubrication
of
ball
bearings
and
ball
thrust
bearings
of
motors
ond
electric
transmitters,
ball
bearing
hongers
of
power
tobles,
etc.
Furnished
in
1 lb. and 4 lb.
tins.
20549
SERVICE
MANUAL
FOR
SINGER.
SEWING MACHINES
OF
CLASS
251
LOCK STITCH
AUTOMATIC OILING
SYST~M
_J
CAUTION
-
See
that
the
oil reservoir
is
filled as
instructed
on
page
5
before
running
the
machine,
even
to
test
the
speed.
THE SINGER MANUFACTURING COMPANY
"A
T,ad,
Ma,k
of
THE
SINGER
MANUFACTURING
COMPANY

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
Copyright
(D
1955,
by
The
Singer
Manufacturing
Company
3
DESCRIPTION
Machines
of
Class 251
are
high
speed,
single
needle,
lock
stitch
machines
with
a
completely
automatic
lubricating
system.
They
have
a
gear
driven,
lubricated,
rotary
sewing
hook
on
a
horizontal
axis
and
a
drop
feed.
The
rotary
sewing
hook
makes
two
revolutions
for
each
stitch.
The
bed
of
these
machines
is
18-3/
4
inches
long
and
7
inches
wide.
The
space
at
the
right
of
the
needle
is
11
inches.
The
machine
base
and
oil
reservoir
furnished
with
these
machines
will
fit
any
table
cut-out
provided
for
Machines
of
Classes
31-,
96-
and
241-.
A
centrifugal
oil
pump
delivers
oil,
under
pressure,
to
all
the
prin-
cipal
bearings.
Provision
is
also
made
to
automatically
lubricate
all
the
other
bearings
in
the
machine.
The
needle
thread
take-up
lever
is
covered
by
an
oil
guard
to
pre-
vent
splashing
of
excess
oil.
An
oil
flow
window,
in
direct
view
of
the
operator,
indicates
the
circulation
of
oil
inside
the
arm
of
the
machine.
The
machine
pulley
furnished
is
for
a
3/8
inch
V-belt.
It
can
be
used
for
a
5/16
inch
round
belt,
when
desired.
These
machines
are
furnished
with
a
knee
lifter,
which
is
an
in-
tegral
part
of
the
machine
base
and
oil
reservoir.
Machine 251-1
has
a
needle
bar
stroke
of
1-9/64
inches
and
a
presser
bar
lift
of
9/32
inch;
can
sew
a
maximum
of
7
stitches
to
the
inch
and
is
designed
for
sewing
light
weight
fabrics.
Machine
251-2
has
a
needle
bar
stroke
of
1-13/64
inches
and
a
presser
bar
lift
of
5/16
inch;
can
sew
a
maximum
of
5-1
/2
stitches
to
the
inch
on
medium-heavy
to
light weight:j:
fabrics.
Machine
251-3
has
a
needle
bar
stroke
of
1-7/16
inches
and
a
presser
bar
lift
of
3 8
inch;
can
sew
a
maximum
of
5-1
/2
stitches
to
the
inch
on
heavy
to
light weight:j:
fabrics.
This
machine
can
also
be
furnished
with
a
presser
bar
lift
of
7
/16
inch,
enabling
it
to
sew
extra-
heavy
to
light weight!:
material.
·/·For
best
performance
on
light
weight
fabrics,
it
is
recommended
that
Machines
251-2
and
251-3
be
equipped
with
fittings
designed
for
the
particular
operation.

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4
SPEED
The
maximum
speed
recommended
for
Machines
251-1
and
251-2
is
5000
revolutions
per
minute
and
for
Machine
251-3,
4300
revolutions
per
minute
according
to
the
material
being
sewn
and
the
type
of
work
being
done.
It
is
advisable
to
operate
these
machines
at
a
more
moderate
speed
the
first
few
days,
after
which
they
can
be
operated
at
maximum
speed.
When
the
machine
is in
operation,
the
top
of
the
machine
pulley
must
always
turn
over
toward
the
operator.
SETTING
UP
When
shipped,
the
base
is
held
to
the
machine
by
a
single bolt
through
the
bottom
of
the
base.
Discard
this
bolt
and
plug
the
hole
by
inserting
from
inside
the
base,
the
special
cap
screw
K,
Fig. 3,
fur-
nished
with
the
machine.
The
base
fits
into
a
standard
table
cut-out
and
rests
on
the
four
corners
without fastening.
Rasp
the
edges
of
the
cut-out,
if
necessary,
as
the base must slide
in
without driving
and
must
be
lo-
cated
so
that
the
machine head
does not touch the table
when
it is
placed
on
the
base.
Use
shims
on
the
corners,
if
nec-
essary,
to
prevent
the
base
from
rocking.
The
base
should
also
be
level
in
both directions
so
that
the
oil
level
will
be
accurately
indi-
H
cated
by
the
marks
in
the
base.
Fig. 2.
Installation
of
Knee
Lifter
See
that
the
plunger
L,
Fig.
3 is in
place
inside
the
base,
before
putting
the
machine
on
the
base.
The
machine
head
rests
on
the
cork
gasket
in
the
base
and
is
not
fastened.
The machine hinges must not support the head
except
when
it is
tilted
back.
The
knee
lifter
is
shipped
assembled
to
the
base,
except
for
the
knee
plate
and
lever
J,
Fig.
2.
After
the
base
is
in
position,
loosen
the
set
screws
D
and
E,
Fig. 2
and
slide
the
shaft
forward
to
the
position
shown
in Fig. 2.
Attach
the
knee
lifter
lever
J.
Set
the
stop
screw
F
so
that
there
is
only a little
play
of
the lifter before it starts
to
lift the
presser
bar,
then
hold
the
screw
and
tighten
lock
nut
G.
Set
the
rear
stop
dog
H
to
allow
the
presser
bar
to
be
just
raised
to
its
limit
but
not
enough
to
permit
further
strain
on
the
knee
lifter
parts
or
to
permit
the
action
of
the
knee
lifter
to
lift
the
machine
from
its
base.
CAUTION:-Before
starting
the
machine,
it
must
be
thoroughly
oiled,
in
accordance
with
the
following
instructions.
s
LUBRICATION
Machines
of
Class
251
have
an
automatic
lubricating
system
in
which
oil is
circulated
from
a
reservoir
in
the
base.
See
X-Ray
view
of
machine
on
pages
24
and
25.
TURN BACK
MACHINE
I
/
.:-:-:::
=--~
/~/
~
K L NEVER ALLOW
FILL
TO
OIL TO
FALL
HIGH
MARK
Fig.
3.
Oil
Reservoir
BELOW LOW
MARK
BEFORE
STARTING
THE
MACHINE,
the
oil
reservoir
must
be
filled
as
instructed
in
Fig.
3,
with
"TYPE
A"
or
"TYPE
C"
OIL,
sold
by
Singer
Sewing
Machine
Company.
For
description
of
these
oils,
see
inside
front
cover
of
this
book.
NOTE:
Before
starting
a
machine
which
has
been
standing idle
for
several weeks,
it
is
advisable
to
remove
the
face
plate
and
oil
the
needle
bar
and
take-up
bearings.
The
automatic
oiling
system
will
lubricate
these
bearings
after
the first
few
minutes.
When
in
operation,
the
oil
level
in
the
reservoir
should
be
inspected
at
least
twice
a
month,
or
as
often
as
necessary,
to
keep
it
from
going
below
the
LOW
mark,
see
Fig.
3, in
the
reservoir.
The
correct
operation
of
the
lubricating
system
is
shown
by
a
continuous
stream
of
oil
passing
through
the
oil
flow
window,
as
shown
in
Fig. 4,
while
the
machine
is
running.
CAUTION
If
the
oil
flow
should
stop,
the
machine
should
be
stopped
and
not
run
again
until
the
cause
has
been
determined.
See
instructions,
covering
Oil
Removing
Wick
Assembly,
on
pages
38
to
41.
SHOULD
SHOW
STEADY
OIL
FLOW
Fig. 4. Oil Flow
Window

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6
ADJUSTMENT OF ROTATING HOOK OIL FLOW REGULATOR
The sewing hook is automatically lubricated. The flow of oil rs
controlled by the oil flow regulator illustrated below.
1 -----· 143350
"~.,, I
, . : "' : ... -~,; _-1=- -b~:::::~
- - ~~'\---=
E2;!4//
~
140551
Fig. 5. Oil Flow Regulator in Hook Shaft Bushing
The oil flow regulator is set at the factory for automatic lubrica-
tion of the hook under average sewing conditions. If more or less oil
is desired, turn the adjusting thumb screw 140551, Fig. 5, clockwise to
increase
the flow of oil to the hook, as indicated by the (+) sign
under its arrow on the head of the thumb screw, or turn it counter-
clockwise to decrease
the flow, as indicated by the (-) sign under its
arrow on the head of the thumb screw 140551.
To determine whether the oil is properly flowing to the hook,
withdraw the bed slide and hold a piece of thin paper under the
hook while the machine runs for ten seconds. There should be a
slight trace of oil on the paper. If there is not, adjust the oil flow
regulator, as instructed above, or replace the oil filter 143350, Fig. 5,
in the head of the hook shaft, as instructed on page 32.
HINTS FOR PERFECT OPERATION
When in operation, the top of the machine pulley must always turn
over toward the operator.
Do not run the machine with the presser foot resting on the feed
without cloth under the presser foot.
Do not run the machine when both bobbin case and needle are
threaded unless there is material under the presser foot.
Do not try to aid the machine by pulling the fabric lest you bend
the needle. The machine feeds the work without assistance.
The slide over the bobbin case should be kept closed when the
machine is in operation.
If the sewing hook should become excessively warm, it may be
due to an insufficient supply of oil lo the hook (see instructions, above,
for adjusting oil flow regulator).
NEVER TOUCH THE STITCH REGULATOR PLUNGER WHILE THE MA-
CHINE IS RUNNING.
7
NEEDLES
Needles for Machines of Class 251 are as follows:
PRESSER
TYPE
NEEDLES
-- - - . - ----
MACHINE
BAR
OF CLASS AND
LIFT MATERIAL VARIETY SIZES
251-1 9
/32 inch Light
88 X 9 8, 9, 10, 11, 12, 13,
14, 16, 17, 18, 19,
20,
21, and 22
- -- - - -
-- ------- - --
------
251-2
5/16 inch Medium-Heavy
8, 9, l 0, 11, 12, 13,
to Light
16 X 257
14, 16, 17, 18, 19,
~-----·-
---- - ----- - -------------- - - - --
20, 21, 22, 23, and
251-3
3/8 inch Heavy to Light
Regular
24
---
251-3 7/16 inch
Extra-Heavy ]6 X 261
16, 18, 19, 21, 22,
to Light and 23
The above needles are regularly nickel finish but are available
with chromium finish if so ordered.
The size of the needle to be used should be determined by the size
of the thread which must pass freely through the eye of the needle.
Rough or uneven thread, or thread which passes with difficulty through
the eye of the needle, will interfere with the successful use of the
machine.
Orders for needles must specify the Quantity required, the Size
number, also the Class and Variety numbers, separated by an x.
The following is an example of an intelligible order:
"l 00 No. 16, 88 x 9 Needles."
The best stitching results will be obtained by using needles sold
by Singer Sewing Machine Company.
THREAD
Left twist thread should be used in the needle. Either right or left
twist thread can be used in the bobbin.
HIS END
l.21974
Fig. 6. How to Determine the Twist
To determine the twist, hold the thread as shown above. Roll the
thread over toward you between the thumb and forefinger of the
right hand; if left twist, the strands will wind tighter; if right twist,
the strands will unwind.

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8
RELATIVE SIZES OF NEEDLES AND THREAD
The following sizes of needles and thread are recommended ac-
cording to the class of work:
SIZES SIZES
OF
OF
CLASSES OF WORK
COTTON, LINEN
NEEDLES OR SILK
Shirtings, Sheetings, Calicoes, Muslins,
60 to 80 Cotton
14
Silks, Dress Goods and all classes of
A and BSilk
general work.
--- --
-·---------------
16 All kinds of heavy Calicoes, light
40 to 60 Cotton
and
Woolen Goods, heavy Silk, Seaming,
C Silk
17 Stitching, etc.
- ------------ ---------
Tickings, Upholstery, Woolen Goods,
30 to 40 Cotton
18 Trousers, Boys' Clothing, Cloaks, etc. D Silk
Heavy Woolens, Tickings, Bags, Heavy
20 to 30 Cotton
19 Coats, Trousers, Heavy Clothing
gen er-
ESilk
ally.
--------
----
21 Bags, Coarse Cloths and Heavy Goods.
TO SET THE NEEDLE
Turn the machine pulley over
toward the operator until the
needle bar moves to its highest
point.
After loosening needle set
screw, insert needle UP into
needle bar AS FAR AS IT WILL
GO, as instructed in Fig. 7.
NOTE: The needle is held in
place, in Machines 251-2 and
251-3, by means of a needle
clamp instead of by means of the
set screw in the needle bar as in
Machine 251-1, illustrated in
Fig. 7.
The single continuous groove
of the needle MUST face the left
end of the machine, as shown
in Fig 7.
----
~
60 to 80 Linen
16 to 20 Cotton
40 to 60 Linen
MOVE TO
~HIGHEST
POINT
(f_~ ---- LOOSEN
SCREW
·~
INSERT
NEEDLE UP
AS FAR AS
POSSIBLE
Securely tighten needle set
screw.
Fig. 7. Setting the Needle
(Machine 25 I• I)
9
UPPER THREADING
NOTE: The take-up lever oil guard should NOT be removed when
threading the machine. It is removed in Fig. 8 only to show the entire
path of the needle thread.
Pass the needle thread from the unwinder through the threading
points in the order shown in Figs. 8 and 9.
0
Fig. 8. Upper Threading
Fig. 9. Threading the Needle
Draw about two inches of thread through the eye of the needle
with which to commence sewing.

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10
TO REMOVE THE BOBBIN
I~
1. MOVE
TAKE-UP
TO HIGHEST
POINT
Fig. 10. Preparing for
Removal of Bobbin
3. HOLD LATCH
AND PULL CASE
FROM HOOK
Turn the machine pulley over
toward the operator, until the
1
needle thread take-up lever is at
its highest point as shown in
Fig. 10.
Reach beneath the bed of
the machine with the ldt hand
and remove the bobbin, as in-
structed in Figs.11 and 12.
2. OPEN
LATCH
Fig. 11. Removing Bobbin Case from Sewing Hook
NOTE: While the latch is kept
open, the bobbin will be retained
in the bobbin case.
To remove the bobbin from
the bobbin case, release the
latch, turn the open end of the
bobbin case downward and the
bobbin will drop out, as shown
inFig.12.
4. RELEASE
LATCH\
5. BOBBIN i
DROPS l
OUT
Fig. 12. Removing the Bobbin
11
TO WIND THE BOBBIN
See Fig. 13.
Fasten bobbin winder to table with its driving pulley in front of
the machine belt, as shown below, so that pulley will move away from
belt when sufficient thread has been wound upon the bobbin.
PLACE BOBBIN
ON SPINDLE
Fig. 13. Winding the Bobbin
Place bobbin on spindle, pushing it on as far as it will go and pass
thread through threading points, as shown above.
Wind end of thread around the bobbin a few times. Press down
on thumb latch, pushing driving pulley over against belt, as shown in
Fig. 13. Start machine.
Bobbin winder will stop automatically, when the amount of thread
for which it is regulated is wound upon the bobbin. For more thread
on bobbin, turn screw A inward; for less thread on bobbin, turn screw
A outward.
When winding a bobbin with fine thread, a light tension should
be used. Adjust the knurled nut X, Fig. 13, to regulate the tension.
If thread winds unevenly on bobbin, loosen screw B and move
tension bracket C to the left or right, as required. Tighten screw B.
Bobbins can be wound while the machine is stitching.
NOTE: Occasionally apply a few drops of oil to the oil well, shown
in Fig. 13, on top of the bobbin winder frame.

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12
TO THREAD THE BOBBIN CASE
Hold the bobbin so that the
thread will unwind in the di-
rection
shown in Fig. 14.
Hold the bobbin case as
shown in Fig. 14 and place the
bobbin into it.
~;~LL
2
► Y { THREAD
DRAW THREAD INTO
UNDER SPRING SLOT
Fig. 15. Pulling the Thread
into the Slot
SLOT
NEAR
TOP
"y,
Fig. 14. Placing Bobbin
in Bobbin
Case
Pull the thread into the slot 1
and under the tension spring 2,
Fig. 15.
3. DRAW
THREAD
INTO ~LIVERY ft
EYE V 'Ji
Draw the thread into the delivery eye
at the end of the tension spring, as shown
in Fig. 16.
Fig. 16. Drawing the Thread
Under the Tension Spring
13
TO REPLACE THE BOBBIN
1. REPLACE BOBBIN CASE
ON STUD
'
2. RELEASE
LATCH
3. PRESS BACK
UNTIL LATCH CATCHES
GROOVE IN STUD
Fig. 17. Bobbin Case Threaded and Replaced
After threading, take bobbin case by latch in the left hand and
place bobbin case on center stud of bobbin case holder, as instructed
in Fig. 17. Release latch. Press bobbin case back until latch catches
groove near end of stud. Allow about two inches of thread to hang free.

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14
TO PREPARE FOR SEWING
Hold slack end of needle thread loosely and turn machine pulley
over toward you until needle moves down and up again to its highest
point, catching bobbin thread. Draw up needle thread; bobbin
thread will come up with it through hole in throat plate, as shown in
Fig. 18. Lay both threads back under presser foot.
fJ
V
Fig. 18. Drawing Up the Bobbin Thread
TO COMMENCE SEWING
Place material beneath the presser foot, lower the presser foot and
commence lo sew, turning the machine pulley over toward you.
15
TO REMOVE THE WORK
1. Let the thread take-up lever rest at its highest point.
2. Raise the presser foot.
3. Draw the work toward the rear until it is clear of the needle.
4. Cut the threads close to the goods.
TENSIONS
For ordinary stitching, the needle and bobbin threads should be
locked in the center of the thickness of the material, thus:
Fig. 19. Perfect Stitch
If the tension on the needle thread is too tight, or if that on the
bobbin thread is too loose, the needle thread will lie straight along
the upper surface of the material, thus:
Fig. 20. Tight Needle Thread Tension
If the tension on the bobbin thread is too tight, or if that on the
needle thread is too loose, the bobbin thread will lie straight along
the under surface of the material, thus:
Fig. 21. Loose Needle Thread Tension

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16
TO
REGULATE
THE
TENSION
ON
THE
NEEDLE
THREAD
lESS
TENSION
Fig.
22.
Regulating
Needle
Thread
Tension
Tension on the needle
thread should be regulated
only
when
the presser foot
is
down.
Tension
on
the
needle
thread
should
be
just
enough
to
set
the
stitch
properly
in
the
material.
Having
lowered
the
presser
foot,
turn
the
thumb
nut
at
the
front
of
the
ten-
sion
discs,
as
instructed
in
Fig.
22.
TO
REGULATE THE TENSION
ON
THE BOBBIN THREAD
When
the
tension
on
the
bobbin
thread
has
been
once
prop-
erly
adjusted,
a
correct
stitch
can
usually
be
obtained
by
varying
the
tension
on
the
needle thread only.
For
average
sew-
ing
the
tension
on
the
bobbin
thread
should
be
very
light.
To
regulate
the
ten-
sion
on
the
bobbin
thread,
remove
the
bobbin
case
and
turn
the
screw
in
the
ten-
sion
spring,
as
in-
structed
in
Fig.
23.
MORE
TENSION
,........_~
__::#
LESS
TENSION
Fig. 23.
Regulating
Bobbin
Thread
Tension
17
TO REGULATE THE LENGTH OF STITCH
BEFORE
DEPRESSING PLUNGER (1)
MAKE
CERTAIN THAT
MACHINE
IS
NOT
RUNNING.
To
change
the
length
of
stitch,
depress
plunger
and
turn
machine
pulley,
over
toward
operator,
slowly,
until
plunger
drops
into
notch
in
the
feed
eccentric,
as
instructed
in
Fig.
24.
Then
turn
machine
pulley,
backward
or
forward,
until
numeral
representing
desired
length
of
stitch is
opposite
the
mark
on
the
front
of
the
arm.
UNTIL
PLU
1.
DEPRESS
_
_/
PLUNGER
....
~
::..,.,
'
'
DRQP.S
INTO N
!I
!l
·l
2. TURN
PULLEY
4.
THEN
TURN
PULLEY
TO
DESIRED
STITCH
LENGTH
Fig.
24.
Regulating
Length
of
Stitch
The
numeral
11
6
11
on
the
stitch
indicator
plate,
shown
above,
indi-
cates
the
longest
possible
stitch;
the
numeral
"30"
indicates
the
shortest
stitch.
Release
the
plunger
when
the
desired
setting
is
obtained.
TO PREVENT OPERATOR
FROM
CHANGING
STITCH LENGTH
The stitch
regulator
plunger
(see Fig. 24)
can
be
removed
to
prevent
an
unauthorized
person
from
changing
stitch
length.
To
remove
the
plunger,
remove
the
retaining
ring
near
the
tip
of
the
plunger,
allowing
the
plunger
to
be
withdrawn.
The
hole
in
the
top
cover
should
then
be
filled
by
inserting
a
plug
screw
140607,
which
can
be
obtained
at
an
additional
charge.