Singer 451k51 Troubleshooting guide

Form K6518
(1266)
SERVICE MANUAL
PARTS LIST
SINGER
451k51
HIGH SPEED
LOCK STITCH
SINGLE NEEDLE
VERTICAL TRIMMER
MACHINE
Machine 451K51
THE SINGER COMPANY
Copyright Under International Copyright Union
•A Trademork of THE SINGER COMPANY
Printed In Greot Britain
From the library of: Superior Sewing Machine & Supply LLC

CONTENTS
Page
DESCRIPTION 3
SETTING UP 4
LUBRICATION 5. 6
INFORMATION FOR OPERATOR 7-14
Page
TIMING AND ADJUSTING 15-22
REMOVAL AND REPLACEMENT OF
PRINCIPAL ASSEMBLIES 23-26
PARTS CHART 28, 29
PARTS LIST 30,31
INDEX
Alignment
Arm Shaft with Hook Driving Shaft
Arm Shaft 15i 25, 26
Arm Shaft Connection Belt 3, 25
Arm Shaft Connection Belt Pulley 25, 26
Automatic Lubrication 6
Ball Bearings and Needle Bearings 15, 25, 26
Bobbin 7
Bobbin Case 8-10,14
Bobbin Case Holder 16, 18, 23
Bobbin Case Holder Needle Guard 16, 18
Bobbin Case Slide
Bobbin Thread 7, 9
Bobbin Thread Tension 10
Bobbin Winder 5» 8
Broken Thread 7, 12
Carefree Operation Hints 14
Centralisation of Feed Dog 21
Change of Stitch Length 11,22
Check-Spring 18, 19
Cleaning 5, 12, 20, 24
Connection Belt, Arm Shaft 3, 25
Common Causes of Stitching Troubles 7
Cover Guard (Take-up) 12, 16
Daily Care 5
Damaged Needles 7
Damaged Parts 14
Dimensions of Machine 3
Drawing Up Bobbin Thread 9
Drip Pan, Installation 4
Face Plate, Removal and Replacement 19
Feed Dog 15, 21, 22
Feed Driving Eccentric Gib 22
Feed Driving and Reversing Mechanism 22
Feed Driving Eccentric 22
Feed Driving Eccentric Adjusting Disc 22
Feed Mechanism (Pendant Link) 3, 16, 21, 22
Feed Movement, Description 21
Feed Reversing Lever Stop Pin 22
Formation of Stitch 10
Fraying of Material 7
Gib
(Feed Driving Eccentric) 22
Hints for Carefree Operation 14
Hook
Clearance to Needle 17
Description 3
Lubrication 6
Removal and Replacement 23
Stringing • 18
Timing 17
Hook Driving Shaft 15, 25
Hook Oil Shield, Installation 6
Hook Oil Wick 6
Hook Section 23
Knee Lifter 3, 4, 14
Knee Lifter Rod Spring 22
Knives
Aligning Upper Knife to Lower Knife 13
Eliminating Side Movement of Knife (Upper)
Holder Bracket 13
Replacing Knives 14
Setting, Lower and Upper Knives to
Correct Height 13
Length of Stitch 3, 11, 22
Light Fixture Mounting Seat 3
Page
15
Page
Locking Feed Driving Eccentric 22
Loop Lift 15
Machine Pulley 3, 5, 14, 25
Machine Rest Pin 4, 14
Machine Storage 5
Needle 7
Needle Bar and Bushing 15-17, 26
Needle Bar Connection Link 26
Needle Bar to Presser Foot, Clearance and
Alignment 20
Needle Bearings 3, 15
Needle Beakage, Prevention 7, 14, 18
Needle to Hook Clearance 17
Needle Guard 16, 18
Needle Threading 7
Needle Thread Tension 10, 18, 19
Needle Thread Tension Releaser 10, 20
Oil Reservoir 3, 5, 25
Oil Shield (Hook) 6
Oil
Wick ( Hook) 6
Pendant Link Feed Mechanism 3
Perfect Stitch 10
Position Finger 6, 17
Preliminary Inspection 15
Preparation for Sewing 9
Presser Bar and Bushing 20
Presser Foot 11, 14, 15, 19, 20
Pressure of Presser Foot 11,22
Prevention of Unauthorised Change of
Stitch Length 22
Puckering 21
Pulley
(Arm Shaft Connection Belt) 25, 26
Pulley, Machine - 3, 5, 14, 25
Removing Broken Thread 12
Rest Pin 4, 14
Reverse Feed 3, 11, 19, 22
Reversing Lever Stop Pin 22
Rock Shafts 24
Rotary Take-up (See "Take-up")
Sewing Hook (See "Hook")
Speed 3, 14
Setting the Needle 7
Specifications 15
Spillage of Bobbin Thread 8
Starting to Sew 12
Stitch Formation 10
Stitch Length 3, 11, 22
Stitch
Regulator 8, 11
Stitching Troubles, Causes 7
Stringing the Needle Guard (Hook) 18
Superfmish 14
Tacking 3, 11,19
Take-up.... 3, 15, 19
Take-up Cover Guard 12,. 16
Tension Devices 3
Tension Releaser (Needle Thread) 20
Threading 7, 9
Thread Beakage 7, 12
Thread Cutters 3, 12
Thread Tensions 10, 19
Trimmer
Adjusting 12
Changing Trimming Margin 12
Disengaging 12
Turning a Corner 12
V-Belt 3
Wearing Checks 6, 15, 20, 21
Winding the Bobbin 8
From the library of: Superior Sewing Machine & Supply LLC

DESCRIPTION
Machine 451 K51, for stitching and trimming
light and medium weight fabrics.
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.
• Reverse feed, hand operated, with spring
return to forward stitch. Performs precise tack
ing and strong seam reinforcing with minimum
thread breakage.
• Maximum stitch length, 6 to the inch
forward and 7 to the inch in reverse.
Vertical Trimmer. Trims 1/8 to 5/16 inch to
the right of seam as desired.
Special fittings for trimming 3/32 inch from
the line of stitching can be furnished if specified
on order. Unless otherwise ordered machine
will be fitted to trim 1/8 inch to right of seam.
The upper knife may be thrown out of action at
will for straight stitching. Upper knife stroke
9/64 inch.
Modified, single rotary take-up maintains
constant thread control to meet hook require
ments. 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
precise 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
rotary tension from broken threads, lint and
other hazards.
Two thread cutters; One, on face plate, pre
vents 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 re
moved.
Large rim, aluminium machine pulley 276445,
for 3/8 inch V-belt, is designed for safety. Out
side diameter 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 a light fixture.
Compact stitch length mechanism is easy to
read and to set.
Enclosed knee lifter rod and connection to
knee lifter 228710.
Needle bar stroke, 1-9/64 (1.140) inches.
Presser bar lift (capacity of machine), 9/32
(.281) inch.
Bed dirnensions: Length, 15-11/16 inches.
Width 7 inches. Working space at right of
needle, 8 inches.
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.
TOP OF MACHINE PULLEY TURNS OVER
FROM THE OPERATOR.
CAUTION
Do not start machine until it has been thor
oughly oiled, as 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 a long
period of time, should be run slower than maxi
mum speed for the first few minutes to allow
time for oil to reach the moving parts. Check
principal bearing points for freedom of move
ment and adequate lubrication before running
machine at top speed.
• Reduce speed of machine when sewing
closeiy 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 con
siderable damage to machine.
From the library of: Superior Sewing Machine & Supply LLC

SETTING 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 avoid 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, ^g. 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
certoin 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.
BELT GUARD
NOTE: Belt Guard 106505 is supplied with
the machine only when requested on order.
Remove arm side cover screw and fit belt
guard bracket 1, Fig. 3 with long hinge screw 2.
Insert belt guard support 3, Into bracket 1, and
belt guard 4, as illustrated. Adjust belt guard
so that It just clears the machine pulley, then
tighten the Allen screws in the bracket and belt
guard with the special key.
FRONT EDGE OF TABLE
PLATFORM
ROCK LEVER ROD—
Fig. 2. Drip Pan and Kne« Lifter
beneath the Table
•>;
Fig. 3. Belt Guard In Position
I ^
'f I
i# ;
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OIL
FILL OIL reservoir:
OIL SHOULD SHOW
AT HIGH MARK —
DIRECTION
OF
ROTATION
NEVER AlToW oil
O FALL BELOW LOW
MARK ON* GAUGE
OIL
OIL
Fig. 4. Oil Reservoir and other
Oiling Points on Machine
Fig. 5. Priming Points beneath
Machine Bed
Fig. 6. Bobbin Winder Lubrication
MACHINE PULLEY
When machine Is In operation, machine pulley
always must turn over away from the operator,
as shown in Fig. 4.
CAUTION: Do not start the machine, not
even to test the speed, until it has been thoroughly
oiled as instructed below.
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 end well oiled at oil times.
OIL RESERVOIR
Fill by lifting out oil gouge 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 four 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.
Occasionally remove the cover for the trimmer
driving crank and apply oil to the oiling points
shown in the insert Fig. 4. Always clean the
cover before replacing it.
AFTER INSTALLATION
New machines and machines installed after several
weeks of idleness should be primed before using.
Residual lubricant
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 above.
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.
From the library of: Superior Sewing Machine & Supply LLC

HOOK LUBRICATION
Rotary sewing hook Is automatically lubri
cated. Flow of oil is regulated by turning screw
N. Fig. 9, as instructed below.
HOOK LUBRICATION TEST
AND ADJUSTMENT
Thread machine, as instructed on pages 7 and 9.
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 o pot-
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 on 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 23.
Loosen filter screw O, Fig. 9 and check oil wick com
plete 276062 (see Fig. 9.) 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
202423 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, as indicated by arrow and word
"MORE" on end of bushing.
Backing screw N out, decreases amount supplied,
as indicated by arrow and word "LESS ".
Normal adjustment is accomplished by turning
screw N in ail 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 poge 23.
Make 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 above. When
hook lubrication is satisfactory, replace all parts
removed earlier.
Fig. 7. Approximate Sproy Pattern
Fig. 8. Rotary Sewing Hook
OILWICK
202423
Fig. 9 Adji/sting Oil Flow to Hook
L I;
MOVE TO
. HIGHEST
POINT
LOOSEN
" SCREW
INSERT NEEDLE
% UP AS FAR AS
POSSIBLE AND
TIGHTEN SCREW
I
^LONG GROOVE
o\ycy-
Fig. 10. Setting Needle
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Use SINGER* needles, Catalogue 1361 (88x9)
made in a variety of sizes.
These needles have a nickel finish but may be
supplied with chromium finish when so ordered.
Chrome plating of sizes 9 and smaller is not
recommended.
ORDERS FOR NEEDLES should specify
Quantity required, Size number and Catalogue
number.
Examples ...
"100 Size 16, Catalogue 1361 (88x9) Needles"
Sizeof 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.
HOLD THIS END
ROLL OVER
TOWARD YOU
Fig, t1. How to Detormine Thread Twist
TO SET THE NEEDLE
Turn machine pulley over away from you until
needle bar is at its highest point, as shown in
Fig. 10, page 6.
Loosen
needle clamping screw. Remove old needle
and insert new needle up into needle bar as far as
it will go.
Make certain that single continuous groove of
needle faces away from hook (toward the left end
of machine, as shown in Fig. 10, page 6) 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 threod 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.
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.
m
WRAP THREAD
l'/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 have become accus
tomed to threading this machine,
thread can be passed from thread
ing point #4 to needle with a single
continuous motion.
MOVE TO
HIGHEST
POINT
Threading the Needle
7 5
to / \\
to (Yi
Fig. 12. Upper Threading Completed
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.
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TO REMOVE BOBBIN
Turn machine pulley over away from you until
needle moves up to Its highest point, as shown in
Fig. 12, Page 7.
Reach beneath bed of machine with left hand and
remove bobbin case 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.
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 releosed from contact with belt
when sufficient thread has been wound upon
bobbin.
PRESS W/
DOWN
TO pushPs
PULLEY i Ib
AGAINST
BELT
START^«s^
MACHINE n
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.
V-j1l\
rr6 m)
Fig. 13. Removing Bobbin Case
from Sewing Hook
ml
3. RELEASE
LATCH
4.BOBBIN
DROPS
OUT
Fig. 14. Removing Bobbin from Case
1. PLACE BOBBIN TENSION
ON SPINDLE CONTROL
\
AS FAR AS—
IT WILL GO
^.=^2. WIND THREAD
note::tTghten around bobbin
FOR MORE THREAD _
ON BOBBIN
Fig. 15. Winding Bobbin
Fig. 16. Plocing Bobbin
in Bobbin Cot*
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3.TURN BOBBIN CASE
OVER AND DRAW
THREAD UP
INTO DELIVERY ^
EYE , _
HRFAirv.Al^
DRAW THREADTN
DOWN AND I
UNDER SPRlN0^
U \\ THREAD
[ INTO
/^SLOT
1(2
Fig. 17. Pulling Thrsod
into the Slot
K'T^dlDING LAt(
gplPL-ACt^BO'BfflT
Fig. 18. Drawing Thread
Under Tension Spring
An LATCH
C3. PRE® -BAOTV,
UNTlt; LAtCW { )
^CATCHES GRO^VE^^
IN STUD ^ i
Fig. 19. Bobbin Cat* Threadod
and Replaced
Fig. 20. Drawing Up Bobbin Thread
TO THREAD BOBBIN CASE
Hold bobbin so that thread will unwind in the
direction shown In Fig. 16, Page 8.
Hold bobbin case as shown In Fig. 16, Page 8
and place bobbin Into it.
Pull thread into slot 1, Fig. 17 and under tension
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 case, 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 hang free.
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.
o Lay both threads back under presser foot.
0 Close bed slide.
Alwoys keep bed slide closed when machine is in
operation.
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THREAD TENSION
For ordinary 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-
sjon 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 rtiachine 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.
InsulTicientpre-tension will causeloopingorthread 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.
10
£30929
Fig. 21. Perfect Stitch
Fig. 22. Needle Thread Tension
Too Tight
Fig. 23. Needle
Thread Tension
Too Loose
£30930
£30922.
Fig. 24. Regulating Bobbin
Thread Tension
MORE
TENSION
LESS TENSK>N
Fig. 25. Regulating Needle
Thread Tension
1=309^
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TURN TO ADJUST
- t
LESS PRG^U
MORE TRE
Fig. 26. Regulating Pressure
on the Material
3 IK! ©115^
BUTTO
Fig. 27. Regulating Stitch Length
DEPRESS FOR REVERSE FEED
STOP PIN
RELEASE FOR FORWARD FEED
Fig. 28. Feed Reversing Lever
m
11
TO REGULATE PRESSURE OF
PRESSER FOOT ON MATERIAL
Correct presser foot pressure helps feed work effi
ciently. You,can 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
(See instructions in Fig. 28)
Simply depress feed-reversing lever shown in
Fig. 28, OS for 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 22.
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12
TO START SEWING
• Move needle bar to top Of its stroke.
• Place material beneath presser foot. Lower
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.
Fig. 29.
E3092S
Removing broken needle thread
from rotary take-up
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 AVOID THREAD BREAKAGE
1. Remove sharp edges from thread-contact
surfaces of all thread handling parts.
2. Check needle and thread as instructed on
page 7.
3. Thread machine correctly, as instructed on
pages 7 and 9.
4. Make certain machine is set for lightest
tensions possible, without loss of thread
control.
5. Keep machine clean and well oiled, at all
times.
TO DISENGAGE TRIMMER
To disengage trimmer, turn up lever A4,
Fig. 31, Page 13, as far as it will go. To re
engage trimmer turn down lever.
TO ADJUST THE TRIMMER
The trimming margin is determined by the
throat plate used. It can be adjusted approxi
mately 1/32 inch for each throat plate by
adjustment of lower and upper knives. Throat
plates can be furnished for 3/32 inch to 5/16 inch
trimming margins as follows :—
# 270646 from 1/8 inch to 5/32 inch
#270647 from 3/16 inch to 7/32 inch
# 270648 from 1/4 inch to 9/32 inch
#270649 for 5/16 inch
#270700 for 3/32 inch using feed dog#270694
Fig. 30. To change the trimming margin
TO CHANGE TRIMMING MARGIN
Loosen bracket clamp screw E4, Fig. 31, Page
13 and move bracket to right. Remove throat
plate and presser foot. Loosen lower knife
bracket clamping screws B3, Fig. 30 and move
bracket to right to allow insertion of throat plate
for desired trimming margin. Then set lower
knife bracket for required trimming margin
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Fig. 31. Adjustment of lower and upper knives
.13
within recommended range of throat plate being
used and firmly tighten clamping screws B3.
With lever A4, Fig. 31, at its lowest position,
turn machine pulley so that knife is about half
way on its downward stroke. Move bracket
until upper knife just contacts lower knife
(excessive contact pressure must be avoided or
cutting edges will chip during operation), ihen
firmly tighten clamp screw E4. After knives
are set, fasten presser foot in machine for desired
trimming margin.
TO SET LOWER AND UPPER KNIVES
TO CORRECT HEIGHT
The lower knife's cutting edge should be set
level with top of throat plate. To make this
adjustment loosen two lower bracket pinch
screws 03, Fig. 30, Page 12, and move knife to
correct height, then firmly tighten two pinch
screws.
To set upper knife to correct height, see that
lever A4, Fig. 31, is at its lowest position, turn
machine pulley until knife is at top of its stroke.
Now loosen screws F4, Fig. 31 and position
upper knife so that bevelled edge at its lowest
point is just beneath cutting edge of the lower
knife then firmly tighten screws F4.
CAUTION.—Do not set knife too low, as
point will strike lower knife bracket.
TO ALIGN UPPER KNIFE TO LOWER KNIFE
Should upper knife not be parallel to lower
knife and gape at forward end of their cutting
edges, turn machine pulley until knife is at
lowest point of its stroke, then loosen screw E4,
Fig. 31 and holding knife holder firmly in its
seating, turn screw D4, Fig. 31 over to right
until correct alignment of the two cutting edges
has been obtained. Tighten screw E4 and check
alignment of cutting edges.
TO ELIMINATE SIDE MOVEMENT OF KNIFE (UPPER) HOLDER BRACKET
In the event of wear taking place between presser bar bushing and forked portion of knife (upper)
holder bracket, loosen nut B4, Fig. 31 and tighten screw C4, Fig. 31 until all play has been eliminated.
Tighten nut B4. When making this adjustment partially withdraw knife driving link hinge stud H4,
Fig. 31, disengaging knife driving link (upper half) in order to ascertain that knife (upper) holder
bracket moves freely on its guides.
From the library of: Superior Sewing Machine & Supply LLC

14
CAUTION: Do not attempt to resharpen the knives with
ordinary grinding wheels as these edges are made of "Tungsten
Carbide" material. It is recommended that worn knives be
replaced with new Upper Knife 270619 and new Lower Knife
270616 to obtain best trimming results.
Be careful to set the knives properly to insure perfect trimming
and prevent chipping of the cutting edges.
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 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 avoid 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 knee 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 "Super-
finish" process provides microscopically smooth bearing surfaces. Therefore, utmost care should be
taken not to permit any misalignment of parts. Anyscratches or nickson bearingsurfaces caused by
careless assembly or handling of parts 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.
From the library of: Superior Sewing Machine & Supply LLC

SPECIFICATIONS
The following gauge distances should be of
help to adjusters.
• Height of presser foot above throat plate
9/32 inch.
• Needle bar stroke 1-9/64 inches.
• Distance from centre-line of needle to point
of hook .015 inch.
• Distance from centre-line of needle to face
of hook shaft bushing .910 to .912 inch.
• Rise of needle bar from lowest position to
position where hook point reaches centre of
needle (LOOP LIFT) .085 inch.
• Height of feed dog above throat plate, .0415
to .0445 inch.
• Clearance between retaining portion of bob
bin 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
variations from these settings.
BALL BEARING
AND NEEDLE BEARING NOTES
There are three ball bearings and four needle
bearings in this machine. With reasonable
care these bearings should enjoy a long and
trouble-free life.
Follow oiling instructions given on pages 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 four needle bearings should receive same
care as ball bearings and should not be removed
from their respective housings except for replace
ment. 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, care should be taken to see that
needle bearings rollfreely in their respective housings.
15
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 page 7.)
3. Threading. (See pages 7 and 9.)
4. Speed of machine. (See page 3.)
5. Lubrication condition. (See pages 5 and 6.)
Before checking and adjusting amachine 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 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
taken 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 16 through
19 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 parts 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 point and
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 overage
sewing, when timing mark E2, Fig. 32, page 16, on
take-up is in line with mark F2, Fig. 32 on face plate,
at same time that mark 02, Fig.33, page 16, is in line
with timing mark H2, Fig. 33 on feed lifting connection.
To adjust for overage sewing conditions, loosen the
two pulley screws A2, Fig. 33; align timing marks E2
and F2, Fig. 32 and turn shaft 82, Fig. 33 as required
to align arrow G2 with mark H2, Fig. 33.
Securely tighten screws A2.
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2. SEHING NEEDLE BAR AT CORRECT
HEIGHT
Turn machine pulley over owoy from you until tim
ing mark E2, Fig. 32 on take-up is in line with mark
F2, Fig. 32 on face plate.
Needle bar should then be at its highest position
and lower timing mark M2, Fig. 32 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. 32 and
loosen needle bar connecting stud pinch screw 12,
Fig. 34, 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. 34.
Raise or lower needle bar as required to bring eye
of needle just above needle guard of bobbin case
holder, as shown in Fig. 35, allowing freedom for
needle thread.
Securely tighten screw L2.
Figures 36 and 37 illustrate opposite extremes of
incorrect settings of needle bar In relation to needle
guard on bobbin case holder.
I
0 AOs
Him
Fig. 32 Timing Mark on Tako-up
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Fig. 33 Timing Mark on Feed
Lifting Connection
\SSL
Fig. 35 Correct Height of Needle
when at Bottom of Stroke
Fig. 36 Needle Too Low
when ot Bottom of Stroke
Fig. 34 Needle Bar Setting
HI 113
Fig. 37 Needle Too High
when ot Bottom of Stroke
From the library of: Superior Sewing Machine & Supply LLC

B30t96 va
J
i
Fig. 38. Timing Marks for Hook
I K R J
Fig. 39. Setting the Hook
CLEARANCE
Fig. 40. Bobbin Case Holder
Position Finger
I
4. TO RESET NEEDLE BAR BUSHING
Remove face plate, as instructed on page 19.
Turn
machine pulley over away from you until
needle bar has reached its highest position.
Drive
needle bar bushing 02, Fig. 32, page 16 up or
down in casting as required to bring its lower end level
with the lower timing mark M2, Fig. 32 on needle bar.
Replace face plate, as instructed on page 19.
5. TO TIME SEWING HOOK
Remove presser foot, slide plate, throat plate, bob
bin cose and feed dog.
Select a needle in good condition and set It in needle
bar as instructed on page 7.
Turn
machine pulley over away from you until
needle bor has started to rise from its lowest position
and timing mark E2 on take-up is in line with mark
on face plote, as shown in Fig. 38.
At this setting, point of sewing hook should be at
centre of needle, as shown in inset in Fig. 39. 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. 39 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 acleorance 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 ond position finger
S, Fig. 39.
Rotate bobbin case holder T, Fig. 39, almost ahalf-
turn, so that needle will not contact needle guard on
bobbin case holder.
Then, loosen set screw J, Fig. 39 on bushing K and
move entire bushing and hook assembly together, as
required; topping 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 case holder posi
tion finger as instructed next.
7. TO SET CLEARANCE FOR BOBBIN CASE
HOLDER POSITION FINGER
Clearance between position finger S, Fig. 40 and
bobbin cose holder, T, Fig. 40 should be just sufficient
to allow thickness of thread to pass through easily.
Normally this requires an .020 inch to .024 inch clear
ance, as shown in Fig. 40.
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.
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8. FUNCTION OF BOBBIN CASE HOLDER
NEEDLE GUARD
Needle guard on bobbin cose holder (see Inset In
Fig.43) should prevent needle fronn contacting hook or
bobbin at all times. In case needle tends to move
sidewlse 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. 41.
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) ore 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. 43 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 15 through 17, 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 cose holder from hookas Instructed on page23.
Remove a 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,
OS shown In Fig. 43.
Extreme care must be taken not to remove too much
metal as this will allow hook point to rub needle, as
shown In Fig. 42, causing wear or damage to needle,
hookand bobbin case holder. Bobbin case 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. 42; 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 23.
10. TO SET CHECK-SPRING
Check-spring setting should be reviewed each time
adifferent foot Is applied to machine.
When machine Is correctly timed, check-spring com
pletes Its downward movement and returns to rest
just as point of needle on Its downward 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. 44 and 46 (with
presser foot resting on throat plate.)
To position check-spring, loosen screw Y, Fig. 44
and remove complete tension assembly. Loosen set
screw N, Fig. 45. Turn thumb nut Q, Fig. 45 out toward
slotted end of stud W, Fig. 45 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. 45. Securely tighten set screw N.
18
HOOK POINT
NEEDLE GUARD
^ BOBBIN
CASE ' ^
HOLDER
Fi9. 41 Correct Relationship
of Needle-Guard to Hook Point
at Loop-taking Time
GUARD
HOOH POINT
NEEDLE GUARD
BOBBIN
Fig. 42 Needle Contacting Hook
Point and Bobbin (Too Much
Metal Removed from Guard)
320 EMm
Fig. 43 Stringing the Needle Guard
Fig. 44 Removing Check-Spring
£30937
Fig. 45 Check-Spring Assembly
Removed from Machine
From the library of: Superior Sewing Machine & Supply LLC

lira O'CLOCK?
o'clock J
f\ ^
6 0 CLOCK
^30938
Fig. 46 Setting the Check-Spring
(g)
Fig. 47 Removing Face Plate
19
10. TO SET CHECK-SPRING (Cont'd)
Make certain that feed dog is below fop 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. 46.
HEIGHT VARIATIONS
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. 46.)
To adjust tension, loosen screw Y, Fig. 47 and re
move entire assembly. Loosen set screw N, Fig. 45,
page 18 and, while holding regulator X, Fig. 45, turn
stud over slightly toward left to increase tension or
toward right to decrease tension. Tighten screw N,
Fig. 45, and replace assembly in machine with spring
at "2 o'clock" as shown in Fig. 46.
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. 32, page 16 and
take-up guard N2, Fig. 32.
2. Remove two screws 02 and rotary take-up
V2, Fig. 47.
3. Loosen screw Y, Fig. 47 and remove needle thread
tension assembly.
4. Remove nine screws F, Fig. 47 and remove thread
guide X, tension threading guide M and face
plate P2, Fig. 47.
REPLACEMENT
1. Install face plate P2, guide M and guide X as
shown in Fig. 47, fastening thern to machine cast
ing with nine screws F, Fig. 47.
2. Replace take-up V2 and two screws 02, Fig. 47.
3. Replace needle thread tension assembly and se
curely tighten set screw Y, Fig. 47.
4. Inspect check-spring setting as instructed on
page 18 and above.
5. Replace take-up guard N2, Fig. 32, page 16 and
securely tighten two screws Z2, Fig. 32.
From the library of: Superior Sewing Machine & Supply LLC

20
TO ADJUST THE NEEDLE THREAD
TENSION RELEASER
Tension releaser J2, Fig. 48 automatically releases
spring pressure on tension discs when presser bar
is raised.
To adjust, loosen screw K2, Fig. 48.
To release tension earlier, raise releaser J2.
To release tension later, lower releaser J2.
When correct setting is obtained, securely tighten
screw K2.
TO SET PRESSER BAR
AT THE CORRECT HEIGHT
PREPARATION
Remove face plate, as instructed on page 19.
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 of
9/32 inch between presser foot and throat
plate.
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. 49 and lifting bracket W2,
as shown in Fig. 49.
3. When presser foot is at its highest point and
needle bar is at its lowest, top of presser foot
should clear the lower end of needle bar M2,
Fig. 49.
SETTING
• Release presser bar lifting lever, lowering presser
foot.
• Loosen clamping screw D2, Fig. 49.
• Raise or lower guide C2, Fig. 49 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 18 and 19.
OTHER ADJUSTMENTS
• Presser bar bushing U2, Fig. 49, should be set
so that its top is even with top of lifting bracket
W2, Fig. 49 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 mokes
with sole of presser foot.
Fig. 48. Adjustment for
Needle Thread Tension Releaser
s
PRESSER 4
FOOT •
RESTING I
FIRMLY T
ON
THROAT\\
PLATE
£30942
Fig. 49. Checking Height of
Presser Bar
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