Singer 451k41 Troubleshooting guide

Form K6S06
(562)
SERVICE MANUAL
PARTS LIST
SINGER
451k41, 451k45 and 451k145
HIGH SPEED
SINGLE NEEDLE
LOCK STITCH
MACHINES
Machine 451K41
THE SINGER MANUFACTURING COMPANY
Copyright Under International Copyright Union
*A Trademork of THE SINGER MANUFACTURING COMPANY
Printed in Great Britain
From the library of: Superior Sewing Machine & Supply LLC

CONTENTS
Page
DESCRIPTION 3
SETTING UP 4
LUBRICATION 4-6
INFORMATION FOR OPERATOR 6-11
Page
TIMING AND ADJUSTING 12-19
REMOVAL AND REPLACEMENT OF
PRINCIPAL ASSEMBLIES 20-23
PARTS LIST 24
INDEX
Alignment
Arm Shaft with Hook Driving Shaft 12
Arm Shaft 12, 22, 23
Arm Shaft Connection Belt 3, 22
Arm Shaft Connection Belt Pulley 22, 23
Automatic Lubrication 5
Ball Bearings and Needle Bearings 12,22,23
Bobbin 7, 8
Bobbin Case 7-9, 11
Bobbin
Case Holder 13, 15, 20
Bobbin Case Holder Needle Guard 13, 15
Bobbin Cose Slide 11
Bobbin Thread 7, 8
Bobbin Thread Tension 9
Bobbin Winder 5, 8
Broken
Thread 7, 11
Carefree Operation Hints 11
Centralization of Feed Dog 18
Change of Stitch Length 10, 19
Check-Spring 15, 16
Cleaning 5, 11, 17, 21
Connection Belt, Arm Shaft 3, 22
Common Causes of Stitching Troubles 6
Cover Guard (Take-up) 11,13
Daily Care 4
Damaged Needles 6
Damaged Parts 11
Dimensions of Machine 3
Drawing Up Bobbin Thread 9
Drip
Pan, Installation 4
Face Plate, Removal and Replacement 16
Feed Dog 12, 18, 19
Feed Driving Eccentric Gib 19
Feed Driving and Reversing Mechanism 19
Feed Driving Eccentric 19
Feed Lifting Eccentric Cam 19
Feed Mechanism (Pendant Link) 3, 13, 18, 19
Feed Movement, Description 18
Feed Reversing Lever Stop Pin 19
Formation of Stitch 9
Fraying of Material 6
Gib (Feed Driving Eccentric) 19
Hints for Carefree Operation 11
Hook
Clearance to Needle 14
Description 3
Lubrication 5^ 6
Removal and Replacement 20
Stringing
Timing
Hook Driving Shaft 12, 22
Hook Oil Shield, Installation 6
Hook Oil Wick 5
Hook Section 20
Knee Lifter 4^ 11
Knee Lifter Rod Spring 19
Length of Stitch 3, 10, 19
Light Fixture Mounting Seat 3
Locking Feed Driving Eccentric 19
Loop Lift 12
Machine Pulley 3, 4, 22
Machine Rest Pin 4, 11
Machine Storage 5
Needle 6
Needle Bar and Bushing 12-14,23
Needle Bar Connection Link 23
Needle Bar to Presser Foot,
Clearance and Alignment 17
Needle Bearings 3, 12
Needle Breakage, Prevention 6,11,15
Needle to Hook Clearance 14
Needle Guard 13, 15
Needle Threading 7
Needle Thread Tension 9, 15, 16
Needle Thread Tension Releoser 9, 17
Oil Reservoir 3, 5, 22
Oil Shield (Hook) 6
Oil Wick (Hook) 6
Pendant Link Feed Mechanism 3
Perfect Stitch 9
Position Finger 6, 14
Preliminary Inspection 12
Preparation for Sewing 9
Presser Bar and Bushing 17
Presser Foot 10, 11, 12, 16, 17
Pressure of Presser Foot 10, 19
Prevention of Unauthorized
Change of Stitch Length 19
Puckering 18
Pulley (Arm
Shaft Connection Belt) 22, 23
Pulley, Machine 3, 4, 11, 22
Removing Broken Thread 11
Rest Pin 4, 11
Reverse Feed 3, 10, 16, 19
Reversing Lever Stop Pin 19
Rock Shafts 21
Rotary Take-up (See "Take-up")
Sewing Hook (See "Hook")
Speed 3, 11
Setting the Needle 6
Specifications 12
Spillage of Bobbin Thread 8
Starting to Sew 11
Stitch
Formation 9
Stitch Length 3, 10, 19
Stitch Regulator
3,10,11
Stitching Troubles, Causes 6
Stringing the Needle Guard (Hook) 15
Superfinish n
Tacking 3, 10, 16
Take-up 3, 12, 16
Take-up Cover Guard 11, 13
Tension Devices 3
Tension Releoser (Needle Thread) 17
Threading 7, 8
Thread Breakage 6, 11
Thread Cutters 3, 11
Thread Tensions 9, 16
Turning a Corner 11
V-Belt 3
Wearing Checks 6, 12, 17, 18
Winding the Bobbin 8
From the library of: Superior Sewing Machine & Supply LLC

DESCRIPTION
Machine 451K41 produces top quality, high speed,
lockstitching on dresses, skirts, shirts, blouses, bras
sieres, lingerie, ladies' overalls, children's wear, sports
wear, rainwear, uniforms, aprons, caps and ties and
many other similar light and medium weight garments.
Particularly designed for "wash and wear" mate
rials, this machine has the following characteristics:
Lock stitch (Stitch Type #301)
Single needle. Catalogue 1361 (88x9)
Socket-type needle bar
Short arm, flat bed
Drop feed. Pendant link feeding mechanism with
reinforced feed bar insures level feed motion and
uniform stitch length at all speeds.
Hinged presser foot 161066
Feed Dog 149031 (19 teeth) (22 teeth to the Inch)
•I It 149057 (21 II ) ( II II 11 II II )
Throat Plate 52033 for 149031
Throat Plate 147150 for 149057
Enclosed knee lifter rod and connections to knee
lifter 228710.
Modified, single rotary take-up maintains constant
thread control to meet hook requirements. Easy to
thread. Simple to adjust.
Long point rotary sewing hook on horizontal axis
(belt driven); automatic lubrication can be regulated.
One oil reservoir and three easily accessible oil
holes
serve all principal bearings in machine.
Rotary tension
and pre-tension devices achieve pre
cise thread control throughout speed range of stitching
with all types of natural and synthetic threads and
materials of light and medium weight—permitting
lightest tensions for perfect "wash and wear" sewing.
Tension guard, mounted on face plate, protects ro
tary tension from broken threads, lint and other
hazards.
Two thread cutters; One, on face plate, prevents
wrapping of broken thread around rotary take-up.
The other, on rear of thread guard, removes excess
broken thread from take-up.
Durable, steel - reinforced, rubber driving belt
270926, from arm shaft to hook driving shaft, is
readily accessible when rear arm cover is removed.
Large rim, aluminium machine pulley 272227, for
3/8 inch V-belt, is designed for safety. Outside diam
eter of belt groove, 2.9 inches. Effective diameter for
5/16 inch round leather belt, 2-3/8 inches.
Tapped hole and seat in rear of arm provided for
mounting alight fixture.
Compact stitch length mechanism is easy to read
and to set.
Maximum length of stitch, 6 to the inch.
Needle bar stroke, 1-9/64 (1.140) inches.
Presser bar lift (capacity of machine), 9/32 (.281)
inch.
Bed dimensions: Length, 15-11/16 inches. Width 7
inches. Working space at right of needle, 8inches.
Double shielded ball bearings at both ends of arm
shaft and at pulley end of hook driving shaft.
Needle bearings for feed driving and feed lifting
connections and for needle bar connecting link.
Nylon insert bearings for feed driving rock shaft
and feed lifting rock shaft.
Controlled pressure lubricated bearings on hook
shaft.
Machine 451K45 is similar to Machine 451K41 ex
cept for these special features . . .
•Reverse feed, hand operated, with spring return
to forward stitch. Performs precise tacking and strong
seam reinforcing with minimum thread breakage.
• Maximum stitch length, 6 to the inch forward
and 7 to the inch in reverse.
• Feed dog 149031
• Throat plate 52033
•Machine pulley 276530: Large rim aluminium pul
ley designed for safety. Outside diameter of belt
groove 2.9 inches. Effective diameter for 5/16 round
leather belt, 2-3/8 inches.
Machine 451K145 is similar to Reverse Feed Machine
451K45 except for these special features . . .
•Designed for light, medium and medium-heavy
fabrics.
• Long arm and bed. Bed dimensions: Length,
18-3/4 inches. Width, 7inches. Working space at
right of needle, 11 inches.
•
Single needle. Catalogue 1969 (135x39).
• Feed dog 149366
• Throat plate 270326
• Needle bar stroke, 1-5/16 inches
• Presser bar lift, 5/16 inches.
CAUTION
Do not start machine until it has been thoroughly
oiled, OS instructed on pages 4, 5 and 6.
SPEED
Maximum speed recommended is 5000 stitches per
minute, with these exceptions . . .
• Run a
new machine at a more moderate speed
the first few days.
• A machine that has been idle, for along period
of time, should be run slower than maximum speed
for the first few minutes to allow time for oil to reach
the moving ports. Check principal bearing points for
freedom of movement and adequate lubrication be
fore running machine at top speed.
• Reduce speed of machine when sewing closely
woven or treated material.
Maximum efficient speed is dependent upon the
nature of the operation, the ability of the operator and
the type of thread and material in use.
Never force machine beyond its maximum efficient
speed for the work being accomplished. Disregard of
this precaution could result in considerable
damage
to machine.
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SEHING UP
DRIP PAN
Position drip pan on underside of table, as shown
in Fig. 2, with its right end even with right inside
edge of machine cut-out in table.
Using four 3/4 inch wire nails, fasten drip pan low
enough in table cut-out to ovoid interference with
rock lever rod (shown in Fig. 2).
KNEE LIFTER
Using three 7/8 inch wood screws (shown at 1,
Fig. 2) fasten rock lever bracket 2 to underside of
table. Locate bracket 2 so that rock lever rod can rise
and fall through hole provided for it in drip pan with
out striking edge of hole.
Locate rock lever extension 3 to hold rock lever rod
equidistant from front and rear edges of hole in drip
pan. Make certain that platform at top end of rod
will be directly under knee lifting rod A, Fig. 5, page 5,
in machine; then securely tighten clamp screw 4.
Raise rock lever rod 5 to bring its platform just
below knee lifting rod in machine, when at rest. Make
certain platform is turned as shown in Fig. 2 and se
curely tighten
clamping screw 6.
Knee plate 7 may be raised, lowered or turned to
suit the requirements of the operator, after loosening
clamping screw 8. Knee plate arm 9 may also be
moved toward the left or right and toward front or
rear, as required after loosening clamping screw 10.
Tighten both screws 8 and 10 securely when correct
position is obtained.
Set stop stud 11 to stop the action of the knee lifter
as soon
as knee lifter raises presser foot high enough
to trip hand lifter on machine. Securely tighten clamp
ing screw 12.
MACHINE HEAD
Machine head should rest upon cushioning pads in
four corners of cut-out in table. Machine is not fas
tened. Machine hinges must not be required to support
head except when machine is tilted back upon ma
chine rest pin on table.
MACHINE PULLEY
When machine is in operation, machine pulley al
ways must turn over away from the operator, as
shown in Fig. 3.
LUBRICATION AND CLEANING
Use SINGER* OIL "TYPE A" or 'TYPE C". See inside
front cover of this book for description of these oils.
Keep machine clean and well oiled at all times.
OIL RESERVOIR
Fill by lifting out oil gauge and applying oil to hole
in machine bed, as instructed in Fig. 4. Reservoir sup
plies oil to sewing hook race, to eccentrics and to
front bushing on hook driving shaft.
DAILY CARE
Apply a few drops of oil to the three oil holes shown
in Fig. 4.
Check oil level in reservoir before starting machine.
Add oil, when necessary to maintain level at HIGH
mark. Never allow oil level to drop below lower mark
on gauge.
t
FRONT EDGE OF TABLE
12 11
t
PLATFORM \N
t
ROCK LEVER ROD—
is
; <TV v<-
Fig. 2. Drip Pan and Knee Lifter
beneath the Table
it
. ^ DIRECTION
OF
ROTATION
Fig. 3. Direction of Rotation
//)7
' - 'I - t
OIL SHOULD SHOW
AT HIGH MARK
CHECK DAILY
FILL
RESERVOIR
OIL
Fig. 4. Oil Reservoir and other
Oiling Points on Machine
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IrrtK-cc-c
1 ! i p llirr
Fig. 5. Priming Points beneath
Machine Bed
OIL
/W\\
'• /// ) \l
/•/// I \
/ •!; a
ii ,^ir'
J {r-
Fig. 6. Bobbin Winder Lubrication
Fig. 7. Approximate Spray Pattern
p) I
Id W Y y ^j
-•''—^^.-^^11 fX' i
j ^ )7^ TTW-A11 \ti I
ir\¥4^zl±^Hi
''SU9/6
Fig. 8. Rotary Sewing Hook
Cy
LUBRICATION AND CLEANING (Cont'd)
AFTER INSTALLATION
New machines and machines installed after several
weeks of idleness should be primed before using.
Residuallubricant may have congealed or disappeared
entirely.
Apply a few drops of oil to priming points shown
in Fig. 5, beneath machine bed.
Oil hook assembly by hand. Check oil flow and
adjust when necessary, as instructed below and on
page 6. Proceed with "DAILY CARE" as instructed on
page 4.
BOBBIN WINDER
Apply a few drops of oil daily, or more often when
necessary, to oil wick in bobbin winder frame as in
dicated in Fig. 6.
CLEANING
Remove all lint and abrasive matter from around
hook and from between feed rows on underside of
throat plate.
Remove dirt from clean-out hole C, Fig. 4 in needle
bar, pushing shank of a needle through hole. Wipe
off all excess oil from areas of machine that may
come in contact with material to be sewn.
Machines not in use should be kept well oiled, clean,
dry and covered.
HOOK LUBRICATION
Rotary sewing hook is automatically lubricated. Flow
of oil is regulated by turning screw N, Fig. 9, as in
structed on page 6.
HOOK LUBRICATION TEST
AND ADJUSTMENT
Thread machine, as instructed on pages 7 and 8.
Sew
about three yards of scrap material.
Remove material. Pay no attention at this time to
stitching quality or amount of oil spray.
Remove bed slide E, Fig. 8.
Run machine for approximately one minute to es
tablish auniform rate of flow. Without stopping ma
chine, hold a piece of white paper underneath hook
for 15 seconds without moving paper during interval.
Remove paper and inspect: There should be a pat
tern of three sprays (two light lines on outside and
one heavier, wider line in centre) as shown in Fig. 7.
If there is no trace of oil or an excess of oil on
test paper
Remove needle, bobbin and bobbin case from ma
chine.
Remove screw R and position finger S, Fig. 8. Loosen
two screws D and remove sewing hook B, Fig. 8 from
hook driving shaft, as instructed on page 20.
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HOOK LUBRICATION (Cont'd)
Loosen filter screw O, Fig. 9 and check oil wick com
plete 276062 (see Fig. 90 Oil wick should be replaced
whenever it has become clogged by lint or dirt from oil.
An excess of oil sometimes indicates that oil wick
276062 has become detached from filter screw.
O, Fig. 9 or that filter screw is not securely tightened.
Repair or replace as required.
Inspect all oil passages in shaft and bushing to see
that they have not become clogged with lint or dirt.
Just plain dirt can prevent oil from reaching its
objective.
The hook shaft bushing K, Fig. 9 contains the regu
lating screw N, Fig. 9 for controlling the oil flow.
Turning in screw N, increases amount of oil sup
plied to hook, OS indicated by arrow and word
"MORE" on end of bushing.
Backing screw N out, decreases amount supplied,
OS indicated by arrow and word "LESS ".
Normal adjustment is accomplished by turning
screw N in all the way, then backing it out again about
2-1/2 turns. Less than 2-1/2 turns may be required
if continuous runs are being made or material with
considerable sizing is being stitched.
To test oil flow while hook is removed from ma
chine, hold test paper under end of hook shaft (with
machine running
at full speed) for 15 seconds. Oil
streak should then be about 1/16 inch wide.
When correct flow is obtained, replace sewing hook
and position-finger, as instructed on page 20.
Moke certain oil shield U is in place as shown in
Fig. 9. It is provided to prevent excess oil from reach
ing underside of throat plate.
Re-test oil flow as instructed at bottom of page 5.
When hook lubrication is satisfactory, replace all parts
removed earlier.
NEEDLES
Machines 451K41 and 451K45
LJse SINGER* needles, Catalogue 1361 (88x9)
made in Sizes 8 to 14 and 16 to 22.
These needles have a nickel finish but may be
supplied with chromium finish when so ordered.
Chrome plating of size 9 and smaller is not
recommended.
Machine 451K145
Use SINGER* needles, Catalogue 1969 (135x
39) made in Sizes 12, 13, 14, 16, 18, 19, 20, 21,
22 and 23.
These needles have a chrome finish.
ORDERS FOR NEEDLES should specify Quantity re
quired, Size number and Catalogue number.
Examples .. .
"ICQ Size 16, Catalogue 1361 (88x9) Needles"
or
"100 Size 16, Catalogue 1969 (135x39) Needles"
Size of the needle to be used should be determined
by type of material being sewn and by size of thread
which must pass freely through the eye of needle.
OILWICK
276062
• I 1 1"'^
Fig. 9. Adjusting Oil Flow to Hook
t
MOVE TO
. HIGHEST
POINT
LOOSEN
SCREW
INSERT NEEDLE
UP AS FAR AS
POSSIBLE AND
TIGHTEN SCREW
LONG GROOVE
Fig. 10. Setting Needle
TO SET THE NEEDLE
Turn machine pulley over away from you until
needle bar is at its highest point, as shown in Fig. 10.
Loosen needle clamping screw. Remove old needle
and insert new needle up into needle bar as far as
it will go.
Moke certain that single continuous groove of needle
faces away from hook (toward the left end of ma
chine, as shown in Fig. 10) with eye of needle directly
in line with arm of machine.
Securely tighten clamping screw.
CHECK NEEDLE OFTEN TO MAKE SURE THESE DEFECTS
ARE NOT PRESENT ...
• Wrong needle for thread and material in use—
a cause of thread breakage.
• Bent needle, clogged needle eye or dirty needle
groove—causes of skipped stitches.
• Hook or burr on needle point—cause of picking
or fraying of material.
• Incorrect setting of needle—a cause of needle
breakage.
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HOLD THIS END
ROLL OVER
TOWARD YOU
Fig. 11. How to Determine Thread Twist
MOVE TO
HIGHEST
POINT
yn
>1
Fig. 12. Upper Threading Completed
i
Sf/y PULL
X A-A mo M:
Fig. 13. Removing Bobbin Cose
from Sewing Hook
A]
\ 1/
A
3. RELEASE
LATCH
4.BOBBiN
DROPS
OUT
Fig. 14. Removing Bobbin from Cose
THREAD
Left twist thread should be used in needle. Either
right or left twist thread can be used in bobbin.
Hold thread as shown in Fig. 11. Twirl thread over
toward you between thumb and forefinger of right
hand; if left twist, strands will wind tighter; if right
twist, strands will unwind or separate.
Rough or uneven thread, or thread which passes
with difficulty through the eye of the needle, will
interfere with successful use of machine.
WRAP THREAD
1*/2 TURNS
AROUND Disc
UPPER THREADING
Turn machine pulley away from
you until
needle is at its highest
position.
Pass thread from unwinder,
through threading points #1
through #12 in order shown in
Fig. 12.
When you hove become accus
tomed to threading this machine,
thread can be passed from thread
ing point #4 to needle with a single
continuous motion.
Thread needle from left to right.
Leave about three inches of
thread behind the presser foot, as
shown in Fig. 12 with which to
start sewing.
TO REMOVE BOBBIN
Turn machine pulley over away from you until
needle moves up to its highest point, as shown in
Fig. 12.
Reach beneath bed of machine with left hand and
remove bobbin cose from sewing hook, as instructed
in Fig. 13.
While latch is kept open, bobbin will be retained
in bobbin case.
To remove bobbin from bobbin case, release latch
and turn open end of bobbin case downward. Bobbin
will drop out, as shown in Fig. 14.
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TO INSTALL BOBBIN WINDER
Bobbin winder should be fastened to table
with its driving pulley approximately 1/4 inch
in front of machine belt, as shown in Fig. 15.
Pulley will then make firm contact with ma
chine belt when thumb latch is pressed down.
Pulley will be released from contact with belt
when sufficient thread has been wound upon
bobbin.
3. •/ /
PRESS v//
DOWN
TO push!
PULLEY I hm
AGAINST
'fwy
—— -ri?'/ ^4^
START^a4-A''''
1. PLACE BOBBIN
~ ON SPINDLE
AS FAR AS _
IT WI|.L GO
TENSION
CONTROL
- LOOSEN
TO ADJUST
FOR EVEN
WINDING
MACHINE
... - 2. WIND THREAD
NOTE-TIGHTEN AROUND BOBBIN
FOR MORE THREAD
ON BOBBIN
Fig. 15. Winding Bobbin
TO WIND 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 bobbin a few times in
direction shown in Fig. 15. Press down on thumb
latch, pushing driving pulley against belt, as shown
in Fig. 15.
Start machine.
Bobbin can be wound while machine is stitching.
TO AVOID SPILLAGE: Regulate bobbin winder to
stop automatically when bobbin is wound approxi
mately 1/16 inch short of bobbin rim.
TO THREAD BOBBIN CASE
Hold bobbin so that thread will unwind in the di
rection shown in Fig. 16.
Hold bobbin cose as shown in Fig. 16 and place
bobbin into it.
SLOT
NEAR
TOP
DRAW THREAD
DOWN AND
Fig. 16. Placing Bobbin
In Bobbin Cose
THREAD
INTO
SLOT
3.TURN BOBBIN CASE
OVER AND DRAW
THREAD UP
INTO DELIVERY ^
EYE ^
Pull thread into slot 1, Fig. 17 and under tension UNDER SPRING
spring 2, Fig. 17
Draw thread into delivery eye at end of tension
spring, as shown at 3, Fig. 18.
TO REPLACE BOBBIN CASE
1. After threading bobbin cose, grasp latch between
thumb and first finger of left hand and place
bobbin case on centre stud of bobbin case holder,
as shown in Fig. 19.
2. Release latch.
3. Press bobbin case back until latch catches groove
near end of stud.
Allow about three inches of thread to hong free.
Fig. 17. Pulling Thread
into the Slot
Fig. 18. Drawing Thread
Under Tension Spring
1.,1. HOLDING LATC^"
!h^EPtACr B0BBIN^2i i^ilEASE LATCH
I'CASEsON STUJ^
3. PRESS-BACK
UNTIL LATCH
CATCHES GI^OOVE
IN STUD
Fig. 19. Bobbin Case Threaded
and Replaced
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1 CS09?A
Fig. 20. Drawing Up Bobbin Thread
LESS T
xu.?
£-5095^
Fig. 21. Perfect Stitch
WJi^'^Au
Fig. 22. Needle Thread Tension
Too Tight
Fig. 23. Needle Thread Tension
Too Loose
MORE
TENSION
J
Fig. 24. Regulating Bobbin
Thread Tension
Fig. 25. Regulating Needle
Thread Tension
TO PREPARE FOR SEWING
(See Fig. 20)
• Hold slack end of needle thread loosely and turn
machine pulley over away from you until needle
moves down
and up again to its highest point, catch
ing bobbin thread.
• Draw up needle thread; bobbin thread will come
up with it through hole in throat plate, as shown in
Fig. 20.
• Lay both threads back under presser foot.
• Close bed slide.
Always keep bed slide closed when machine is in
operation.
THREAD TENSION
Forordinary stitching, tension on needle and bobbin
threads should be balanced with needle and bobbin
threads locked in centre of thickness of material as
shown in Fig. 21.
When there is too much tension on needle thread
or not enough on bobbin thread, needle thread can
not be pulled down into material, as required. Poor
stitching results. Needle
thread lies on top of material
as shown in Fig. 22.
When there is too much tension on bobbin thread
and not enough on needle thread, you get the reverse
of the condition shown in Fig. 22. The stitching is just
as poor. Bobbin thread lies on bottom of material as
shown in Fig. 23.
NEEDLE THREAD TENSION SEHING
FOR GENERAL PURPOSES
When machines leave the factory, the needle thread ten
sion thumb nut is set to a position for sewing most light
and medium threads without adjustment.
Should this setting be lost, the minimum tension at which
the machine will sew a medium thread should be established.
At this setting a variety of threads can be sewn.
TO REGULATE BOBBIN THREAD TENSION
For average sewing, tension on bobbin thread
should be very light.
To regulate tension on bobbin thread, remove bob
bin case and turn screw in tension spring, as instructed
in Fig. 24.
When once the tension on bobbin thread has been
correctly adjusted for ordinary stitching, required
stitch can usually be obtained thereafter to suit the
work in process by varying tension on needle thread
only.
TO REGULATE NEEDLE THREAD TENSION
Before the initial needle thread tension adjustment,
obtain the correct tension on bobbin thread, as in
structed above.
Tension on needle thread should be just enough
to set stitch correctly in material.
Regulate needle thread tension only when presser
foot is down. Needle thread tension is automatically
released when presser foot is raised.
Having lowered presser foot, turn thumb nut at
front of tension discs, as instructed in Fig. 25.
PRE-TENSION SEHING
The purpose of this tension is to ensure that the needle
thread grips the rotary tension wheel.
Insufficient pre-tension will cause looping or thread break -
age with heavy materials and thread. Excessive pre-tension
will make it impossible to get a sufficiently light needle
thread tension when using very light threads.
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TO REGULATE PRESSURE OF
PRESSER FOOT ON MATERIAL
Correct presser foot pressure helps feed work effi
ciently. You con regulate amount of pressure exerted,
by means of screw on top of arm, as shown in Fig. 26.
Pressure on material should be as light as possible,
while sufficient to insure correct feeding.
To increase pressure turn this screw downward
(clockwise).
To reduce pressure turn this screw upward (anti
clockwise).
Do not completely release pressure on presser
foot otherwise the ball bearing on the top of the
presser bar may be displaced.
Pressure is correct when work moves steadily and
smoothly without stalling.
TO REGULATE THE LENGTH OF STITCH
Maximum length of stitch: 6 to the inch.
To change the length of stitch . . .
• STOP machine
• Depress button in machine bed as instructed in
Fig. 27 and
• Turn machine pulley over away from you
slowly . . .
• Until button drops (clicks).
• Then turn machine pulley, until
number indicating
desired stitch length is opposite mark P, Fig. 27 on
arm, and release button.
Never depress button while machine is running.
Make certain that button is disengaged before starting
machine.
TO REVERSE THE FEED
ON MACHINES 451K45 and 451K145
(See instructions in Fig. 28)
Simply depress feed-reversing lever shown in
Fig. 28, as far as it will go.
Feeding in reverse continues only as long as lever
is held in depressed position.
Forward feeding is resumed upon release of lever.
Direction of feed can be reversed at any point in a
seam while machine is in operation, without disturb
ing the work. Back tacking is therefore readily accom
plished and ends of seams are easily fastened.
For adjustment of stop pin, shown in Fig. 28, see
instructions at bottom of page 19.
10
TURN TG^ADJUST
MORE PRESSURE
LESS PRESSURE
Fig. 26. Regulating Pressure
on the Material
E
BUTTON
---J" ^
Fig. 27. Regulating Stitch Length
DEPRESS FOR REVERSE FEED
STOP PIN
RELEASE FOR FORWARD FEED
Fig. 28. Feed Reversing Lever
From the library of: Superior Sewing Machine & Supply LLC

t
Fig. 29.
TO REMOVE BROKEN NEEDLE THREAD
FROM ROTARY TAKE-UP
If needle thread breaks at operating speeds, an
extra piece may be found in take-up which is visible
through grille G, Fig. 29.
Open grille G, as shown in Fig. 29 and remove
thread.
Close grille G and rethread.
When removing end of thread from take-up, care
should be taken to avoid injury from thread cutter
H, Fig. 29.
TO START SEWING
• Move needle bar to top of its stroke.
• Place material beneath presser foot. Lovy^er presser
foot.
• Start to sew, turning machine pulley over away
from you.
TO TURN A CORNER
• Stop machine when needle is rising but before
it is out of material.
•Raise presser foot.
• Turn material for next line of stitching, using
needle as a pivot.
•Lower presser foot.
• Resume sewing.
TO REMOVE THE WORK
•Stop machine when needle bar has just started
to descend. In this position upper thread will be free
of the sewing hook and take-up will not unthread
needle when machine is started.
•Raise presser foot.
• Draw work toward rear until it is clear of needle.
• Cut threads close to material.
3.
4.
TO AVOID THREAD BREAKAGE
Remove sharp edges from thread-contact surfaces
of all thread handling parts.
Check needle and thread as instructed on pages 6
and 7.
Thread machine correctly, as instructed on pages 7
and 8.
Make certain machine is set for lightest tensions
possible, without loss of thread control.
Keep machine clean
and well oiled, at all times.
15 HINTS FOR CAREFREE OPERATION
1. Oil machine regularly. Inadequate lubrication is the surest way to rapid deterioration of moving parts.
2. Don't apply oil to hook through holes in throat plate. Keep machine clean.
3. Occasionally remove accumulation of lint and abrasive matter from around hook and from between feed
rows on underside of throat plate.
4. Make certain that when machine is in operation, machine pulley always turns over away from operator.
5. Always use needle that corresponds in size to thread in use.
6. To ovoid rapid wear of feeding surfaces on feed dog and presser foot, do not run machine with presser
foot resting on feed dog without some fabric under presser foot.
7. Do not run machine when both bobbin case and needle are threaded unless there is material under presser foot.
8. Keep slide over bobbin case closed when machine is in operation.
9. Never run machine with take-up cover open.
10. To avoid damaging needle, do not try to help machine by pulling fabric. Machine feeds the work without
assistance.
11. Do not press kne'e lifter lever while machine is in operation, as this might prevent the work from feeding
properly.
12. NEVER TOUCH STITCH REGULATOR BUTTON WHEN MACHINE IS RUNNING.
13. Use machine rest-pin on table to support machine when working beneath machine bed.
14. Reduce speed of machine when sewing closely woven or treated fabrics.
15. Never force machine beyond its maximum efficient speed for the work being accomplished.
Machines of Class 451K are made with extreme precision in machining and assembly, and "Superfinish" process
provides microscopically smooth bearing surfaces. Therefore, utmost care should be token not to permit any
misalignment of parts. Any scratches or nicks on bearing surfaces caused by careless assembly or handling of
ports might render a machine incapable of the long, trouble-free service for which it was designed.
NOTE: The instructions on the following pages are for Service Representatives.
To insure correct timing and avoid unnecessary repetition, these instructions should be followed in the
order given.
11
From the library of: Superior Sewing Machine & Supply LLC

SPECIFICATIONS
The following gouge distances should be of help to
adjusters of these machines ...
•
Height of presser foot above throat plate:
Machines 451K41 and 451K45, 9/32 inch.
Machine 451K145, 5/16 inch.
• Needle bar stroke:
Machines 451K41 and451K45, 1-9/64 Inches.
Machine 451K145, 1-5/16 inches.
• Rise of needle bar from lowest position to position
where hook point reaches centre of needle (LOOP
LIFT):
Machines 451K41 and 451K45, .085 inch.
Machine 451K145, .100 inch.
•Height of feed dog above throat plate, .0415 to
.0445 inch.
•Clearance between retaining portion of bobbin
case holder position finger and bobbin case holder,
.020 to .024 inch.
• Clearance between bobbin case holder and side
edges of bobbin case position finger, .020 to .024 inch.
Certain conditions of sewing may necessitate slight
variations from these settings.
BALL BEARING
AND NEEDLE BEARING NOTES
There are three ball bearings and three needle
bearings in each of these machines. With reasonable,
care these bearings should enjoy a long and trouble-
free life.
Follow oiling instructions given on pages 4, 5 and 6,
carefully.
When handling bearings outside of machine, care
should be token to see that no foreign matter gets
into these bearings.
Ball bearings on forward end of arm shaft and
rear end of hook driving shaft are forced fitted into
their correct position at factory and should not be
removed except for replacement.
When replacing ball bearings, make certain that
shielded side is always out (on less protected side)
and that they form a tight fit on their respective shafts.
Ball bearing on machine pulley is also a forced fit.
The three needle bearings should receive some care
as ball bearings and should not be removed from their
respective housings except for replacement. Needle
bearings should be replaced by pressing on numbered
end of outside shell.
Any pressure on unnumbered end may distort shell
and cramp bearings.
After installation, core should be taken to see that
needle bearings roll freely intheir respective housings.
PRELIMINARY INSPECTION
Before any unnecessary time and effort is spent
making major adjustments or installations, check fol
lowing conditions of machine performance.
1. Sample of work currently produced on this ma
chine.
2. Needle and thread in use. (See pages 6 and 7.)
3. Threading. (See
pages 7 and 8.)
4. Speed of machine. (See page 3.)
5. Lubrication condition. (See pages 4, 5 and 6.)
Before checking and adjusting a machine that has
been idle for some time, check for hardened oil or
grease between moving parts. Dip machine in Varsol
or a
similar cleaning compound and remove all hard
ened lubricant. Then oil machine completely as in
structed on pages 4, 5 and 6.
After a machine has had considerable use, check
for worn out parts, loose-fitting shaft, eccentrics, forks
and links, bent needle bar, presser bar and needle,
damaged hook, throat plate, presser foot and feed
dog. Replace all parts showing wear with SINGER*
parts for top-performance.
TO TIME THE MACHINE
Timing the machine consists of first adjusting the
radial position of sewing hook with relation to move
ment of needle bar and needle thread take-up, so
that loop of thread cast out by needle will be correctly
token by point of hook at proper time for desired
stitch formation. Check-spring and feed are then timed
to synchronize their motions with needle and hook
movements.
Timing instructions below and on pages 13 through
16 should be followed in exact order given for efficient
results.
1. TO TIME THE ROTARY TAKE-UP AND
ARM SHAFT WITH HOOK DRIVING SHAFT
Take-up and other ports on these shafts are cor
rectly timed
when their locating screws are in shaft
splines provided for them.
These locating screws have a cone-shaped pointand
are the first screws to appear when shafts are re
volved in their normal direction of rotation.
Arm shaft and hook driving shaft (with their com
ponents) ore in time with each other, for average
sewing, when timing mark E2, Fig. 30, page 13, on
take-up is in line with mark F2, Fig. 30 on face plate,
at same time that mark G2, Fig. 31, page 13, is in line
with timing mark H2, Fig. 31 on feed lifting connection.
To adjust for average sewing conditions, loosen the
two pulley screws A2, Fig. 31; align timing marks E2
and F2, Fig. 30 and turn shaft B2, Fig. 31 as required
to align arrow G2 with mark H2, Fig. 31.
Securely tighten screws A2.
12
From the library of: Superior Sewing Machine & Supply LLC

-7^<S
\
:3Vv>, V /j
->A \y Jj '•
y/z/u & ZfZ's
^ // •.'0^-^ Aj ! \ '
• f- ZZ/y
'rteU '
!(
T>
I ^ \ \ V
NM
Fig. 30. Timing Mark on Take-up
/i I \
1_| 11 rnf 1J| fy
I -)! I ' i/ \ i&Wf I' '
^zJ)y , U I 'f- ' ^ Zl> /
Fig. 31. Timing Mark on Feed
Lifting Connection
BOBBIN
CASE
HOLDER
NEEDLE
GUARD
Fig. 33. Correct Height of Needle
when at Bottom of Stroke
2. SETTING NEEDLE BAR AT CORRECT
HEIGHT
Turn machine pulley over away from you until tim
ing mark E2, Fig. 30 on take-up is in line with mark
F2, Fig. 30 on face plate.
Needle bar should then be at its highest position
and lower timing mark M2, Fig. 30 on needle bar
should be just visible below lower end of needle bar
bushing.
To set needle bar at correct height, remove two
screws Z2 and rotary take-up guard N2, Fig. 30 and
loosen needle bar connecting stud pinch screw 12,
Fig. 32, through hole in face plate. Move needle bar
to correct height and securely tighten screw L2.
3. TO SET NEEDLE BAR AT CORRECT
HEIGHT WITHOUT USE OF TIMING MARK
(when needle bar bushing has been disturbed)
Turn machine pulley over away from you until
needle bar is at bottom of its stroke.
Loosen screw L2, Fig. 32.
Raise or lower needle bar as required to bring eye
of needle just above needle guard of bobbin case
holder, as shown in Fig. 33, allowing freedom for
needle thread.
Securely tighten screw L2.
Figures 34 and 35 illustrate opposite extremes of
incorrect settings of needle bar in relation to needle
guard on bobbin case holder.
£30 927
BOBBIN
CASE
HOLDER
NEEDLE
GUARD
Fig. 34. Needle Too Low
when at Bottom of Stroke
13
Fig. 32. Needle Bar Setting
BOBBIN
CASE
HOLDER
NEEDLE
GUARD
Fig. 35. Needle Too High
when at Bottom of Stroke
From the library of: Superior Sewing Machine & Supply LLC

4. TO RESET NEEDLE BAR BUSHING
Remove face plate, as instructed on page 16.
Turn machine pulley over av/ay from you until
needle bar has reached its highest position.
Drive
needle bar bushing 02, Fig. 30, page 13 up or
down in casting as required to bring its lower end level
with
the lower timing mark M2, Fig. 30 on needle bar.
Replace face plate, as instructed on page 16.
5. TO TIME SEWING HOOK
Remove presser foot, slide plate, throat plate, bob
bin case and feed dog.
Select a needle in good condition and set it in needle
bar as instructed on page 6.
Turn machine pulley over away from you until
needle bar has started to rise from its lowest position
and timing mark E2 on take-up is in line with mark
on face plate, as shown in Fig. 36.
At this setting, point of sewing hook should be at
centre of needle, as shown in inset in Fig. 37. Note
that when sewing hook is correctly timed, hook point
will be in centre of needle scarf and approximately
1/32 inch above needle eye.
To relocate radial position of hook and correct the
timing, loosen two screws at D, Fig. 37 in hub of hook.
Turn hook on its shaft, as required. Tighten two
screws D.
6. CLEARANCE BETWEEN NEEDLE AND
POINT OF HOOK
Point of hook should pass needle scarf as closely
OS possible without striking or deflecting needle. This
is achieved by setting aclearance equal to about the
thickness of a piece of note paper.
Hook body should always be located, on the shaft,
by pressing it all the way on the shaft.
When it is necessary to move hook sidewise in rela
tion to needle, remove screv/ R
and position finger
S, Fig. 37.
Rotate bobbin case holder T, Fig. 37, almost ahalf-
turn, so that needle will not contact needle guard on
bobbin case holder.
Then, loosen set screw J, Fig. 37 on bushing K and
move entire bushing and hook assembly together, as
required; tapping bushing K away from needle (toward
right) or prying bushing K with hook assembly closer
to needle (toward left) with a screwdriver against
bed casting.
When hook and bushing are in correct position in
relation to needle, securely tighten screw J.
Recheck timing of hook, as instructed above.
Replace all parts removed earlier.
Check thread clearance for bobbin cose holder posi
tion finger as instructed next.
7. TO SET CLEARANCE FOR BOBBIN CASE
HOLDER POSITION FINGER
Clearance between position finger S, Fig. 38 and
bobbin cose holder, T, Fig. 38 should be just sufficient
to allow thickness of thread to pass through easily.
Normally this requires an .020 inch to .022 inch clear
ance, as shown in Fig. 38.
Bend finger Scarefully to achieve this setting.
Make certain that top surface of finger S will be
level with top of bobbin case holder T.
14
Fig. 36. Timing Marks for Hook
SCARF
HOOK
POINT
D K J
Fig. 37. Setting the Hook
y
: .022
j CLEARANCE
Fig. 38. Bobbin Case Holder
Position Finger
From the library of: Superior Sewing Machine & Supply LLC

HOOK POINT
NEEDLE GUARD
BOBBIN
CASE
HOLDER
HOOK POINT
NEEDLE CiUARD
/
BOBBIN
Fig. 39. Correct Relptionship Fig. 40. Needle Contacting Hook
of Needle-Guord to Hook Point Point and Bobbin (Too Much
at Loop-taking Time Metal Removed from Guard)
320 EMERY
NEEDLE
Fig. 41. Stringing the Needle Guard
©
Fig. 42. Removing Check-Spring
£30937
Fig. 43. Check-Spring Assembly
Removed from Machine
8. FUNCTION OF BOBBIN CASE HOLDER
NEEDLE GUARD
Needle guard on bobbin cose holder (see inset in
Fig. 41) should prevent needle from contacting hook or
bobbin at all times. In case needle tends to move
sidewise toward hook point during the crucial loop-
taking period, needle guard should deflect toward
left (away from the hook) sufficiently to prevent dis
aster, as shown in Fig. 39.
When all settings are correct it is usually not neces
sary for needle guard to deflect needle at loop-taking
time.
When large needles (Sizes 22 to 24) are used needle
guard may deflect needle too for toward left at the
bottom of needle stroke and cause breakage of needle
on bobbin cose holder at base L, Fig. 41 of position
finger slot.
This breakage can be avoided by stringing back
needle guard, as instructed below, until needle does
not deflect too for at the bottom of its stroke. Before
doing this, check and adjust machine as described on
pages 12 through 14, in exact order given.
9. TO STRING THE NEEDLE GUARD
When it becomes necessary to string the needle
guard to provide more clearance for needle, remove
bobbin case holder from hook as instructed on page 20.
Removea slight amount of metal from needle guard,
by using a 1/8 inch strip of very fine emery cloth
(about #320), holding one end of the emery cloth in
a vise
and rubbing edge of needle guard along strip,
as shown in Fig. 41.
Extreme care must be taken not to remove too much
metal as this will allow hook point to rub needle, as
shown in Fig. 40, causing wear or damage to needle,
hook and bobbin cose holder. Bobbin cose holder may
then have to be discarded and new one installed in
its place.
Removing even more metal from guard can expose
bobbin, permitting needle to strike it as shown in
Fig. 40; damaging needle or bobbin. Broken or dam
aged parts should be replaced by parts in good con
dition.
Be sure to clean bobbin cose holder thoroughly, be
fore placing it back in hook as instructed on page 20.
10. TO SET CHECK-SPRING
Check-spring setting should be reviewed each time
a different foot is applied to machine.
When machine is correctly timed, check-spring com
pletes its downward movement and returns to rest
just OS pointof needleon itsdownward stroke,reaches
level of top surface of throat plate.
HEIGHT
Check-spring should be set in its assembly so that
when it completes its action it will come to rest 1/4
inch above thread pull-off V, Figs. 42 and 44 (with
presser foot resting on throat plate.)
To position check-spring, loosen screw Y, Fig. 42
and remove complete tension assembly. Loosen set
screw N, Fig. 43. Turn thumb nut Q, Fig. 43 out toward
slotted end of stud W, Fig. 43 to protect stud and (in
serting screwdriver in slot of stud W) rotate stud and
check-spring as required to position spring correctly
in regulator X, Fig. 43. Securely tighten set screw N.
15
From the library of: Superior Sewing Machine & Supply LLC

10. TO SET CHECK-SPRING (Cont'd)
Make certain that feed dog is below top surface of
throat plate and that presser foot is resting on throat
plate. Place complete assembly in machine so that
check-spring loop (at rest) is in "2 o'clock" position,
about 1/4 inch above thread pull-off V as shown in
Fig. 44.
HEIGHT VARIATIONS (FOR REVERSE FEED MACHINES)
Under certain conditions of tacking it may be nec
essary to set check-spring higher than it is otherwise
normally set.
TENSION
Tension of check-spring should be set so that when
machine is sewing 16 stitches per inch at 5000 R.P.M.,
spring will overthrow beyond the "5 o'clock" position
but not beyond the "6 o'clock" position. (See Fig. 44.)
To adjust tension, loosen screw Y, Fig. 45 and re
move entire assembly. Loosen set screw N, Fig. 43,
page 15 and, while holding regulator X, Fig. 43, turn
stud over slightly toward left to increase tension or
toward right to decrease tension. Tighten screw N,
Fig. 43, and replace assembly in machine with spring
at "2 o'clock" as shown in Fig. 44.
TENSION VARIATIONS
The required tension on check-spring may vary, de
pending upon the thread and material used. Heavier
thread and bulkier material require more tension to
ensure correct thread control.
TO REMOVE AND REPLACE FACE PLATE
REMOVAL
1. Remove the two screws Z2, Fig. 30, page 13and
take-up guard N2, Fig. 30.
2. Remove two screws 02 and rotary take-up
V2, Fig. 45.
3. Loosen screw Y, Fig. 45 and remove needle thread
tension assembly.
4. Remove nine screws F, Fig. 45 and remove thread
guide I, tension threading guide M and face
plate P2, Fig. 45.
REPLACEMENT
1. Install face plate P2, guide M and guide I as
shown in Fig. 45, fastening them to machine cast
ing with nine screws F, Fig. 45.
2.
3.
4.
Replace take-up V2 and two screws Q2, Fig. 45.
Replace needle thread tension assembly and se
curely tighten set screw Y, Fig. 45.
Inspect check-spring setting as instructed on
page 15 and above.
5. Replace take-up guard N2, Fig. 30, page 13 and
securely tighten two screws Z2, Fig. 30.
16
Q2
2o'clockI
^^>^5 O'CLOCKJ
u
6 0 CLOCK
^30938
Fig. 44. Setting the Check-Spring
P2
Fig. 45. Removing Face Plate
From the library of: Superior Sewing Machine & Supply LLC

Fig. 46. Adjustment for
Needle Thread Tension Releaser
PRESSER 4
FOOT •
RESTING 1
FIRMLY T
ON
THROAT
PLATE
Fig. 47.' Checking Height o?
Presser Bar
TO ADJUST THE NEEDLE THREAD
TENSION RELEASER
Tension releaser J2, Fig. 46 automatically releases
spring pressure on tension discs when presser bar
is raised.
To adjust, loosen screw K2, Fig. 46.
To release tension earlier, raise releaser J2.
To release tension later, lower releaser J2.
When correct setting is obtained, securely tighten
screw K2.
VARIATION
To prevent premature release of tension, when stitch
ing heavy material, releaser J2 should be set lower
than when stitching light work.
TO SET PRESSER BAR
AT THE CORRECT HEIGHT
PREPARATION
Remove foctf plate, as instructed on page 16.
Remove slide plate.
Test presser bar for smooth, uniform motion. If
presser bar tends to stick at any point, feeding will
be adversely affected. Presser bar may need cleaning, .
repairing or replacement.
Accumulation of lint, oil and dirt on presser foot
seat on presser bar may prevent proper seating of
foot. Clean this area before checking and setting the
presser bar.
CHECK
1. When presser foot is raised with presser bar
lifting lever there should be a clearance between
presser foot and throat plate:
•
9/32 inch for Machines 451K4I and 451K45
• 5/16 inch for Machine 451K145
2. When presser foot rests firmly upon throat plate
(with feed, dog below throat plate) there should
still be some clearance between presser^bar po
sition guide C2, Fig. 47 and lifting bracket W2,
as shown in Fig. 47.
3. When presser foot is at its highest point and
needle bar is of its lowest, top of presser foot
should clear the lower end of needle bar M2,
Fig. 47.
SETTING
• Release presser bar lifting lever, lowering presser
foot.
• Loosen clamping screw D2, Fig. 47.
• Raise or lower
guide C2, Fig. 47 as required.
• Make certain presser bar is turned correctly so
that needle will locate centrally between the two toes
of the presser foot.
• Securely tighten screw D2.
Review setting of check spring, as instructed on
pages 15 and 16.
OTHER ADJUSTMENTS
•Presser bar bushing U2, Fig. 47, should be set
so that its top is even with top of lifting bracket
W2, Fig. 47 when bracket is all the way down.
• Presser foot should offer as little resistance as
possible to material. Check bottom surface of foot for
wear or abrasion; particularly at angle that toe makes
with sole of presser foot.
17
From the library of: Superior Sewing Machine & Supply LLC

TO Time the feed
Feeding movement Is correctly timed, for average
sewing conditions, by setting up the following align
ment;
• Timing line G2, Fig. 48 on feed driving eccentric
collar in line with timing line H2 on feed lifting con
nection, OS shown in Fig. 48, at same time that timing
line E2, Fig. 49 on rotary take-up is in line with timing'
line F2 on face plate, as shown in Fig. 49.
This alignment (see page 12) is set up before ma
chine
leaves factory.
When correctly timed ...
• The feed dog stops its feeding action and drops
below the throat plate before the needle enters
the material on its downstroke.
•" The feed dog begins its feeding action after
the needle has risen above the material.
IF FOR ANY REASON IT MAY BE NECESSARY TO
ALTER TIMING OF FEED ...
• Set machine for longest stitch, as instructed on
page 10.
• Loosen two screws A2, Fig. 48 on pulley.
• Turn hook driving shaft B2, Fig. 48, as required
to obtain desired feeding movement.
• Then securely tighten two screws A2.
• Test-run machine to make certain that desired
timing is achieved.
• Test feed assembly linkage for freedom of move
ment, Action of
feed dog must be regular and smooth
for maximum efficiency.
. Re-timesewing hook, as instructed on page 14.
TO ELIMINATE PUCKERING OF MATERIAL: Advance
feed timing very slightly.
TO CENTRALIZE FEED DOG IN
THROAT PLATE SLOTS
CHECK
Feed dog should not contact edges of throat
plate slots.
SIDEWISE SETTING
Feed dog should travel on a line midway
between sides of throat plate slots.
Feed dog can be moved toward left or right,
OS required, after loosening two screws J3 and
screw C3, Fig. 50.
By moving bearing centres at K3, Fig. 50
toward left or right, as required, rock shaft
H3, feed bar G3 and feed dog can be-moved
to desired position.
Moke certain that bearing centres K3 will
hold rock shaft H3 snugly in place without
binding, then securely tighten two screws J3.
LENGTHWISE SETTING
Set machine for longest stitch as instructed on
page 10.
Feed dog should be set so that its movement is
equidistant from front and rear edges of throat plate
slots.
18
K3 J3
\
Fig. 48. Timing the Ffied
I ,-r • ".^1. -.v -'jC
V //
'•\\v ;
Fig. 49. Timing Morks on Toke-up
and on Face Plate
JO Jut
^ i'\ hi f'V\Y®ii/h
!lrL -I 2U:1 ^1
iB I I
J3 K3
Fig. 50. Adjusting the Feed Dog
Loosen pinch screw M3, Fig. 50 and move feed bar
G3 and rock shaft H3, as required.
Securely tighten screw M3.
Set feed dog at correct height.
From the library of: Superior Sewing Machine & Supply LLC

Z3 P3 03
Fig. 51. Adjusting the Feed Eccentrics
U3 1
Fig. 52. Adjusting the Reverse
Feed Mechanism
(Machines 451K45 and 451K145)
TO SET FEED DOG AT CORRECT HEIGHT
Before checking height of feed dog, set machine
for longest stitch, as instructed on page 10.
When feed dog is at its highest position, rear teeth
of feed dog should project above top surface of throat
plate, .0415 inch to .0445 inch.
Variations of feed dog height may be necessary
to balance height with presser foot pressure.
To adjust height of feed dog, loosen pinch screw
C3, Fig. 50, in feed lifting crank and raise or lower
feed bar G3, Fig. 50, as required.
When feed dog is set to desired height, securely
tighten screw C3.
TO ADJUST FEED REVERSING LEVER
STOP PIN
Top of stop pin, shown in Fig. 28, page 10, is nor
mally set 5/16 inch above bottom of lever slot. This
setting determines maximum stitch length that ma
chine will sew in reverse when lever is fully depressed.
To adjust, loosen nut S2, Fig. 50, page 18 and turn
stop pin R2, Fig.50 upward or downward, as required.
If stop pin R2 is set too low, hinge stud U3, Fig. 52
will strike side of oil reservoir beneath machine bed.
Securely tighten nut S2 when correct setting is
obtained.
TO ADJUST FEED DRIVING
ECCENTRIC GIB
Feed eccentric Is provided with a gib Q3, Fig. 51
which can be adjusted to. take-up any loose motion
between feed driving eccentric and eccentric body.
To adjust gib, loosen two locking screws R3, Fig. 51
nearest gib Q3; then turn in two adjusting screws
S3, Fig. 51
against gib until all ploy is eliminated and
eccentric fits snugly in slot in eccentric body. Securely
tighten the two locking screws R3.
TO PREVENT UNAUTHORIZED CHANGE OF
STITCH LENGTH
Tighten adjusting socket screws S3, Fig. 51 firmly
and securely tighten locking screws R3, Fig. 51. Feed
driving eccentric X3, Fig. 51 will then be locked and
stitch length cannot be changed.
TO ADJUST FEED LIFTING ECCENTRIC CAM
A spring held by collar Z3, Fig. 51 presses against
feed eccentric cam to prevent it from moving out of
position
during operation. Ordinarily, collar Z3 should
be
set flush with end of hub of eccentric body, as
shown.
To adjust, loosen set screw Y3. This set screw must
enter timing groove in eccentric body when it is re-<
tightened.
TO CHECK THE KNEE LIFTER ROD SPRING
Spring P3, Fig. 51, between bed casting and collar
03, Fig. 51, on knee lifter lifting rod, cushions action
of lifting bracket.
Occasionally inspect this spring to moke certain it
is in good working condition.
TO ADJUST FEED DRIVING AND
REVERSING MECHANISM
(Machines 451K45, 451K145) ' '
Position in which crank W3, Fig. 52 is secured to
feed reversing shaft determines actual travel of feed
dog with respect to setting of feed driving eccentric
X3, Fig. 51.
Correct position can best be obtained by trial.
Set eccentric X3 to 6 stitches per inch, as instructed
on page 10. Place clean pieceof paper beneath presser
foot. Lower presser foot. DO NOT DEPRESS FEED RE
VERSING HANDLE. Loosen pinch screw V3, Fig. 52 and
rotate crank W3 on its shaft until exactly 6needle
punctures per inch' can be obtained on the paper.
Securely tighten screw V3.
Machine is now correctly set for 6 stitches per inch,
forward, and will produce a slightly shorter stitch in
reverse when feed reversing lever is fully depressed
as instructed on page 10.
19
From the library of: Superior Sewing Machine & Supply LLC

THE BOBBIN CASE HOLDER
REMOVAL
Remove needle.
Remove bobbin case and bobbin, as instructed on
page 7.
Remove large screw R and position finger S, Fig. 53.
Turn hook body B, to position shown in Fig. 53 and
remove three small screws A4 and hook-section
C4, Fig. 53.
Turn bobbin cose holder in hook to position shown
in Fig. 53 and slip bobbin case holder out of hook.
REPLACEMENT
Turn hook B to position shown in Fig. 53.
Install bobbin case holder T in hook body, keeping
holder T in the relative position to hook body shown
in Fig. 53.
Replace hook section C4, fastening it to hook body
with three small screws A4, Fig. 53.
Turn bobbin case holder T as required to bring
thread clearance notch L at top of holder ready to
accept position finger S, as shown in Fig. 53.
Replace position finger S, as shown in Fig. 53 fast
ening it to machine with screw R.
Set thread clearance of position finger, as instructed
on page 14.
Replace needle, as instructed on page 6.
THE SEWING HOOK
REMOVAL
Remove needle, slide plate and bobbin cose. Re
move screw R, Fig. 54. Remove bobbin case holder
position finger S, Fig. 54. Loosen two screws D,Fig.54
in hub of hook. Turn machine pulley over away from
you until feed bar G3, Fig. 55 is raised to its highest
point. Turn sewing hook until thread guard F3 is at
the bottom, as shown in Fig. 54. Turn bobbin case
holder until it is in position shown in Fig. 55.
Remove sewing hook from machine.
While sewing hook is off shaft, check oil wick
276062, as instructed on page 6.
REPLACEMENT
When replacing sewing hook on shaft, have thread
guard F3, Fig. 55 at bottom of hook and bobbin case
holder T turned to position shown in Fig. 55, so that
hook will clear feed bar G3. Press hook all the way
on shaft.
Turn bobbin case holder T, Fig. 53 until notch L is
at top, OS shown in Fig. 53. Replace position finger
S, Fig. 54, being careful to see that position finger
enters notch L at top of bobbin case holder, as shown
in Fig. 54. Securely fasten position finger S by meons
of screw R, Fig. 54. Replace bobbin case, slide plate
and needle.
Time sewing hook, as instructed on page 14.
20
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if I \ \ \ I
Fig. 53. Position of Bobbin Case
Holder, in Relation to Hook;
Necessary for Removal or Replacement
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1 fyf'
ij -Ji
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ih
Fig. 54. Sewing Hook in Place
Fig. 55. Position of Hook
in Relation to Feed Bar;
Necessary for Removal or Replacement
From the library of: Superior Sewing Machine & Supply LLC