Singer 20U31 User manual

Service Manual
SINGER*
20u31/33/35
MACHINES
THE SINGER COMPANY

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
CONTENTS
Description
Sewing
Defects
and
Adjustments
To·Set
Needle
Bar
at
Correct
Height
Relation
Between
Needle
and
Rotating
Hook
To
Adjust
Sidewise
Movement
of
Needle
while
in
the
Material
(Zigzag
Stitching)
To
Adjust
Needle
Location
in
Relation
to
Needle
Hole
in
Throat
Plate
.
To
Obtain
Uniform
Straight
Stitch
To
Set
Feed
Dog
at
Correct
Height
To
Centralize
Feed
Dog
in
Throat
Plate
Slots
To
Set
Presser
Bar
at
Correct
Height
Timing
the
Feed
Positioning
the
Feed
and
Feed
Lifting
Eccentric,
Feed
Forked
Connection,
Feed Rock
Shaft
Crank,
Feed
Lifting
Rock
Shaft
Crank
Connecting
Rod
and
Feed
Lifting
Rock
Shaft
Crank
Adjustment
of
Tension
.
Adjustment
of
Backlash
,.. A
Trod~marlr
of
THE SINGER
COMPANY
Copyri9ht
O
1980
THE
SINGER
COMPANY
All
Rights
Aes.rn,ed
Throughout
the
World
Page
1
2
3
4
5
6
14
14
15
17
18
20
20
22

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
DESCRIPTION
Model 20U artisan machine produces top quality straight and zigzag
stitches in fabrics as fine as ladies' lingerie or as heavy as overcoating.
GENERAL FEATURES
* Rotating hook
*
Link take-up
* Stitch length controlled by feed regulating dial
* Needle position selector places stitching in left, center or right needle
positions
* Spring biased stitch width selector which can also be set at desired stitch
width
SPECIFICATIONS
* Maximum stitch width
* Maximum stitch length
* Needle bar stroke
* Height of presser foot from top surface
of throat plate
* Thread take-up lever stroke
* Needle bar height (Distance from throat
plate seat to needle stop in needle bar
at its lowest position)
* Speed - up to 5 mm stitch width
over 5 mm and up to maximum
stitch width
* Diameter of machine pulley (for motor
drive)
- 1 -
9mm
5 s. p. i. (5 sti tches/25 .4 nnn)
34.8 mm
6.35 mm
63.5 mm
25.07 mm
2,500 r.p.m.
2,000 r.p.m.
75 mm (3 in.)

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
SEWING
DEFECTS
AND
ADJUSHIENTS
ects
Need
le
Thread
Skip
Looping, Improper Uneven
Breakage Brec1kage
Stitching
Stagger
&
Feeding
Puckering
Zigzag
Noise
Place
of
Adjustmen~
Hitch
Stitch
Stitches
1. Thread -
X
X
X
-X
2.
Need
1e
X X X
X -X
X
3. Needle Bar X X
X ----X
4.
Rotating
Hook
-X X
----X
s.
Bobbin Case -
X
-X -X
6. Needle
Thread
Tension
-X -X X X
X
N
7. Thread Take-up Lever -
X
---
--X
8.
Presser
Foot X
X X
-
X
X
9.
Feed ----
X
X -X
10,
Throat
Plate
X
X --X
11. St i t ch
\~
i
cl
th X
12. Needle
Position
X
13,
Material
X
--- - X
X
14. Gear
-
------
X

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
TO
SET
NEEDLE
BAR
AT
CORRECT
HEIGlIT
OlECK:
1.
Remove
face
plate.
2.
Set
needle
position
selector
on
"center"
and
stitch
width
regulator
for
straight
stitching.
3.
Turn
machine
pulley
over
toward
you
until
needle
descends
to
its
lowest
position.
4.
Check
whether
upper
timing
mark
on
needle
bar
is
level
with
underside
of
needle
bar
timing
indicator
plate.
CAUTION:
The
needle
bar
timing
indicator
plate
has
been
correctly
positioned
at
the
factory
and
it
SHOULD
NOT
BE
DISTURBED.
ADJUSTMENT
:
If
needle
bar
is
not
set
at
correct
height,
then
adjustment
should
be
made
as
instructed
belm,.
1.
With
machine
set
for
straight
stitching
at
center
needle
pos1t1on,
turn
machine
pulley
until
ntedle
bar
is
at
its
lowest
position.
2.
Loosen
needle
bar
set
screw
so
that
only
the
needle
bar
will
move
up
and
down
freely.
3.
Move
needle
bar
up
or
down
as
required,
and
align
its
upper
t1m1ng mark
with
underside
of
needle
bar
timing
indicator
plate.
Then
securely
tighten
needle
bar
set
screw.
4.
Replace
face
plate.
Needle
Bar
Connecting
Stud
Fig.
1
- 3 -
Needle
Bar
Timing
Indicator
Plate
Needle
Bar
Set
Screw
Needle
BaT

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
RELATION
BETWEEN
NEEDLE
.AND
ROTATING
HOOK
A.
TO
TIME
TIIE
ROTATING
HOOK
CHECK:
1.
Set
needle
position
selector
on
"center"
and
stitch
width
regulator
for
straight
stitching.
2.
Turn
machine
pulley
over
toward
you
until
needle
rises
2.54
ma
from
its
lowest
position
and
the
lower
timing
mark
is
level
with
the
underside
of
needle
bar
timing
indicator
plate.
When
the
needle
bar
is
in
the
above
position,
the
point
of
rotating
hook
should
be
at
the
center
of
the
needle
as
shown
in
Fig.
2.
ADJUSTMEN1:
If
the
t1m1ng
of
rotating
hook
in
relation
to
the
needle
requires
correc-
tion,
make
adjustments
as
instructed
below.
1.
Set
machine
for
straight
stitching
at
center
needle
position.
2.
Remove
rotating
hook
shaft
bevel
gear
cover.
3.
Loosen
two
rotating
hook
set
screws
and
adjust
rotating
hook
as
required.
Retighten
set
screws.
'
Needle
'I
Hook
Point
;I
0.5
2.42
2.57
:
I:
I
4.25
:
I.
I
I
I '
I
2.54
r
'
' ' I
\j/
1.21
'I'
)'.
\I/
'j,c
'
Left
Needle
Position
Center
Needle
Position
Right
Needle
Position
Fig.
2
B.
~HECK
TIMING
OF
ROTATING
HOOK
AND
NEEDLE
(AT
LEFT,
CENTER
AND
RIGITT
NEEDLE
POSITIONS)
1.
Turn
machine
pulley
over
toward
you and make
sure
the
needle
is
free
from
any
interference
when
it
is
swung from minimum
to
maximum
bight
at
left,
center
and
right
needle
positions.
- 4 -

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
2. Set stitch width regulator for straight stitching and check (visually)
whether the relationship between needle and rotating hook is as shown in
Fig. 2 (at center and left needle positions) just when needle Tises from
its lowest position.
3. Be sure the clearance between needle and hook
point is O - 0.05 mm (Fig. 3) regardless of left,
center, or right needle pasitions. Excessive
clearance may result in skip stitching.
Adjustment should be made in the same way as
explained in paragraph A, "TO TIME THE ROTATING
HOOK".
TO ADJUST SIDEWISE MOVEMENT OF NEEDLE
WHILE IN TI-!E MATERIAL (ZIGZAG STITCHING)
0 - 0.05
Hook Point
Needle
Fig. 3
When zigzag stitching, the needle must not move sidewise while its point
is still in the material, or in the needle hole in throat plate. The-needle
should make its upward or downward movement only after completing its swing
to the left or right as shown in Fig. 4.
v v
l'
/ ' I '
✓'
/
";
'
.,
.,
I ' ' /
I ' ,
~
~
'
-- '
/
' /
'
✓
' ,
I
\.
A I
\
,.
' I
I + " ~
,t
It-
I
I \
/ \
I '
A
, '
..
! '
I '
...
.,
• I
I '\ \ I
~~
Correct Wrong Wrong
Fig. 4
Fig. 5-a
Fig. 5-b
If the needle continues its swing even as it enters the needle hole in
throat plate, or when it begins to rise as shown in Fig. 5-a and 5-b, such
condition should be corrected by making the following adjustments.
·- 5 -

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
ADJUSTMENT:
1.
Turn
machine
pulley
over
toward
you
until
needle
bar
is
at
its
lowest
position.
2.
Remove
screws
and
lift
off
arm
top
cover.
Loosen
the
zigzag
triangular
cam
shaft
collar
set
screw
and
slide
collar
toward
front
of
machine.
Check
whether
the
two
zigzag
triangular
cam
set
screws
(with
center
line
aligned)
are
located
parallel
to
the
bearing
face
of
the
zigzag
stitch
Tegulator
fork.
3.
If
the
triangular
cam
set
screws
are
not
located
parallel
to
the
bearing
face
of
the
stitch
regulator
fork,
loosen
arm
shaft
(horizontal)
worm
gear
set
screws
and
turn
arm
shaft
worm
gear
as
required
until
the
triangular
cam
set
screws
are
in
either
one
of
the
two
positions
shown
in
Fig.
6.
Then
securely
tighten
arm
shaft
worm
gear
set
screw.
4.
Check
rith
a
dial
gage
(Fig.
11)
to
see
whether
the
needle
is
still
making
sidewise
movement
while
in
the
fabric
and
below
throat
plate,
and
if
necessary,
readjust
as
instructed
above.
CHECK:
Zigzag
Triangular
Cam
Set
Screw
To
Be
Par
all
el
---\✓
---
Fig.
6
TO
ADJUST
NEEDLE
LOCATION
IN
RELATION
TO
NEEDLE
HOLE
IN
THROAT
PLATE
To
Be
Parallel
--'{
---
1.
Fit
needle
to
needle
clamp.
(Make
sure
the
needle
is
not
bent.)
2.
Set
needle
position
selector
on
"center"
and
stitch
width
regulator
for
straight
stitching.
- 6 -

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
4.
Turn
iaachine
pulley
slowly
until
needle
descends
into
the.needle
hole
in
throat
plate
(for
zigzag
stitching)
and
check
whether
or
not
the
needle
is
properly
located
in
the
center
of
the
needle
hole
(Fig.
7).
s. Change
throat
plate
to
straight
stitching
throat
plate,
lower
needle
hole
and
check
whether
it
is
properly
centered
or
not.
plate
to
zigzag
stitching
throat
plate.
needle
into
Change
throat
6.
Move
stitch
width
regulator
to
maximum
stitch
width
and
while
holding
regu-
lator
in
this
position,
turn
machine
pulley
and
check
left
and
right
needle
locations
in
relation
to
the
center
of
needle
hole
in
throat
plate.
Also
check
left
and
right
needle
locations
in
relation
Lo
the
needle
hole
with
need.le
position
set
at
left
and
right
of
center.
-
Center
~
l~
Fig.
7
Fig.
8
Fig.
9
ADJUSTMENT:
If
the
needle
location
is
offset
to
the
left
or
to
the
right
of
center
and
the
clearance
between
needle
and
edge
of
hole
at
left
and
right
is
not
equal,
or
if
needle
continues
to
swing
even
when machine
is
set
for
straight
stitching,
and
if
for
any
reason
it
is
necessary
to
replace
and
adjust
related
parts,
then
adjust
as
instructed
below.
A.
TO
ELIMINATE SIDEWISE
MOVEMENT
OF
NEEDLE
WHEN
MAO-HNE
IS
SET
FOR
STRAIGITT
STITOiING
1.
Fit
needle
plug
to
needle
clamp.
(Make
needle
plug
by
grinding
down
the
point
of
a
needle.)
Fig.
10
- 7 -
rr:2
i~=t
20
mm

From the library of Superior Sewing Machine & Supply LLC - www.supsew.com
2.
Loosen and Temove arm
side
cover.screws
..and.rernove
side
cover.
Remove
arm
top
cover
screws
and
lift
off
top
cayer.
3.
Set
needle
position
selector
on
"center"
and
stitch
width
regulator
for
straight
stitching.
4.
Turn
machine
pulley
over
toward
you and check
existence
of
sidewise
movement
of
needle.
(Fig.
11)
5.
If
there
is
a
sidewise
movement
in
the
needle,
loosen
bight
amplitude
stop
plate
(left)
set
screw
and move
left
bight
amplitude
stop
plate
(marked with
asterisk)
to
the
left
or
right
as
required,
until
the
sidewise
movement
is
eliminated.
(Fig.
12)
Check,
using
a
dial
gage
lFig.
11),
and
make
sure
the
sidewise
movement
(if
any)
is
held
to
less
than
0.05
and
securely
tighten
set
screw.
Needle
Bar Frame
Fig.
11
- 8 -