Singer 491D User manual

SERVICE MANUAL FOR SINGER 491D SEWING MACHINE
PARTS CHART FOR 491D200GA & 491D300GA
SEWING MACHINE
*

Restored from web copy
Available from
Internet Archive
archive.org

Form U251 (1273)
T H E S I N G E R C O M PA N Y
Service Manual
Machine
491D
*

CONTENTS
Page
* A Trademark of THE SINGER COMPANY
Copyright © 1973 THE SINGER COMPANY
All Rights Reserved Throughout the World
Description of Machine . . . . . . . . . . . . . . . . . . . . 1
ADJUSTMENTS
To set Needle Bar at Correct Height . . . . . . . . . . . . . 2
To Set Check Spring Height . . . . . . . . . . . . . . . . . . 2 - 3
To Set Check Spring Tension . . . . . . . . . . . . . . . . . 3
To Set Presser Bar at Correct Height . . . . . . . . . . . . . 4
To Time the Sewing Hook and also Set the Sewing
Hook Sidewise in Relation to the Needle . . . . . . . . . . 5
Feed Reverse Lever . . . . . . . . . . . . . . . . . . . . . . 6
To Time the Feed . . . . . . . . . . . . . . . . . . . . . . . 6
To Set Feed Dog at Correct Height . . . . . . . . . . . . . . 7
REMOVAL AND REPLACEMENT OF PRINCIPAL ASSEMBLIES
To Remove the Sewing Hook . . . . . . . . . . . . . . . . . . 8
To Replace Oil Filter 143042 . . . . . . . . . . . . . . . . . 9
To Replace the Sewing Hook . . . . . . . . . . . . . . . . . . 9
To Remove and Replace the Hook Shaft . . . . . . . . . . . . . 10
The Oil Pump . . . . . . . . . . . . . . . . . . . . . . . . . 11
To Remove and Replace the Upright Arm Shaft . . . . . . . . . 12 - 13
To Remove and Replace the Needle Bar . . . . . . . . . . . . . 13
To Remove and replace the Presser Bar . . . . . . . . . . . . 14
Needle Thread Take-up . . . . . . . . . . . . . . . . . . . . 14 - 16
To Remove and Replace Arm Side Shield Wick, Needle
Bar Wick and Needle Bar Connecting Stud Wick . . . . . . . 16
To Remove Oil Wick Holder . . . . . . . . . . . . . . . . . . 17
To Install New Oil Wick Holder . . . . . . . . . . . . . . . . 17 - 18
The Arm Shaft . . . . . . . . . . . . . . . . . . . . . . . . 18 - 21

DESCRIPTION
Class 491D Machines are high speed, rotary hook, fully automatic lubricated
long arm flat bed lockstitch machines with drop feed and hand operated reverse
feeding mechanism. Recommended for general stitching operations on a range of
light to heavyweight fabrics.
- 1 -
GENERAL FEATURES
Balanced horizontal axis rotating hook.
Pendant link feed with feed leveling hinge pins.
Dial type stitch regulator on feed reverse lever,
Thread take-up lever guard. Equipped with improved head end lubrication.
Knee lifter mechanism is integral with the machine base and oil reservoir.
Arm top cover with oil flow indicator.
The arm is provided with a seat for mounting a light fixture.
SPECIFICATIONS
Needle bar stroke 30.5 mm - 491D200AA
36.5 mm - 491D300AA
Clearance under presser foot 7.2 mm - 491D200AA
7.9 mm - 491D300AA
(Maximum lift of presser foot when raised with knee lifter - 12.7 mm)
Maximum stitch length 6 S.P.I.
Maximum speed 5,500 S.P.M. - 491D200AA
5,000 S.P.M. - 491D300AA
Oil SINGER* Type "C" Oil
Bed size 475 mm x 178 mm

58.73 mm − 491D200AA
66.01 mm − 491D300AA
- 2 -
TO SET NEEDLE BAR AT CORRECT HEIGHT
Fig. 2
THROAT PLATE
SEAT
TIMING
MARK
PREPARATION:
Remove face plate, slide
plate and throat plate. See
that needle is correctly set
in needle bar.
Lower end of bushing A,
Fig. 2 must be set as shown
in Fig. 2. To reset bushing,
loosen screw B.
CHECK:
When needle bar is at its
lowest point (during rotation
of machine pulley), UPPER
TIMING MARK on needle bar
should be level with lower end
of bushing.
Check timing of hook as
instructed on page 5.
SETTING:
Loosen clamping screw C, Fig. 2. Raise or lower needle bar so that UPPER
TIMING MARK is level with lower end of bushing. Then securely tighten screw C.
Replace throat plate and slide plate.
When replacing the face plate, make certain that the screw holes in the
face plate gasket are aligned with the respective screw holes in the face plate;
avoiding injury to the gasket and consequent oil leakage.
TO SET CHECK SPRING HEIGHT
PREPARATION:
Thread the machine and place a lightweight material under presser foot.
CHECK:
Turn machine pulley over toward operator slowly. When take-up lever
begins to rise, check spring D, Fig. 3 makes a slight dip and a return to its
higher position. Later, as take-up lever approaches top of stroke, check
spring D should be drawn all the way down; setting the stitch. As lever de-
scends, check spring D returns to rest.
C
B
A

- 3 -
SETTING:
Loosen screw E, Fig. 3. Turn stud F,
Fig. 3 (at the same time turning entire ten-
sion assembly) either over toward left to
lower check spring and decrease its movement,
or over toward right to raise check spring
and increase its movement. Securely tighten
set screw E.
NOTE: Under certain conditions of
tacking, it may be necessary to set the
check spring higher than it is otherwise
normally set.
CAUTION: Check spring height setting
must be checked each time a different foot
is applied to machine.
TO SET CHECK SPRING TENSION
PREPARATION:
Thread the machine, securely tighten
set screw E, Fig. 4. Make certain thumb nut
is on stud F, fig. 4.
CHECK:
Tension on check spring D, Fig. 4,
should be sufficient to ensure action at top
speed; but still light enough to permit it-
self to be drawn all the way down (as take-
up lever approaches height of stroke) before
any thread is drawn through the tension
discs.
SETTING:
Using a large screwdriver in slot of
stud F, turn stud either over toward left to
decrease tension or over to right to in-
crease it, as shown.
NOTE: The tension on the check spring may require different settings
depending upon the size of thread used. Heavier thread requires more tension
to ensure correct thread control.
Fig. 3
Fig. 4
D
F
E
HIGHER
LOOSEN
LOWER
D
E
F
TIGHTEN
MORE
TENSION
LESS
TENSION

- 4 -
TO SET PRESSER BAR AT CORRECT HEIGHT
Fig. 5 Fig. 6
PREPARATION:
Remove face plate and slide plate.
CHECK:
1. When presser foot rests firmly upon throat plate (with feed dog below throat
plate) there should still be some clearance between guide bracket G, Fig. 5
and lifting lever link H, as shown in Fig. 5.
2. When presser foot is at its highest point and needle bar is at its lowest,
top of presser foot should clear lower end of needle bar, as shown in Fig. 6.
SETTING:
Loosen clamping screw J, Fig. 5. Raise or lower guide bracket G, as
required. Securely tighten screw J.
CAUTION: Whenever guide bracket has been moved on presser bar, inspect the
check spring for correct setting, as instructed on pages 2 and 3.
G
J
H
CLEARANCE
FOOT
RESTING
FIRMLY
UPON
THROAT
PLATE
AT LOWEST
POINT
JUST
CLEAR
AT HIGHEST
POINT

- 5 -
PREPARATION:
Remove presser foot, slide plate, throat
plate and feed dog.
CHECK:
When lower timing mark on needle bar is
level with lower end of lower needle bar
bushing A as shown in Fig. 7, the point of the
sewing hook should be at the center of the
needle, as shown in Fig. 7.
Also, when point of sewing hock passes
needle, clearance between hook point K,
Fig. 8 and needle should be approximately
equal to thickness of a piece of ordinary
notepaper (about .13 mm), as shown in Fig. 9.
NOTE: Not only point of sewing hook
but entire "FLAT" of hook point should clear
scarf on needle blade. Normally, a .5 mm
clearance is provided between hub of hook
and oil retaining collar.
SETTING:
Loosen two set screws L, Fig. 7 in hub
of hook. Then retighten one of the set
screws very lightly so that the sewing hook
can still be turned on the shaft.
Hold shaft immovable and turn hook as
required to bring point of hook to center
of needle as shown in Fig. 7 and at the same
time adjust clearance between needle and
hook point as shown in Fig. 9.
Tighten set screws L lightly, turn
machine pulley to make certain the sewing
hook is correctly set in relation to the
needle. Then securely tighter set screws L.
TO TIME THE SEWING HOOK AND ALSO SET THE
SEWING HOOK SIDEWISE IN RELATION TO THE NEEDLE
Fig. 7
Fig. 8
Fig. 9
K
HOOK
POINT
NOTEPAPER
FLAT OF
HOOK POINT
LOWER
TIMING
MARK
HOOK POINT
AT CENTER
OF NEEDLE
ON UPWARD
STROKE
A
L

- 6 -
FEED REVERSE LEVER
Before the machine leaves the factory, the
spring tension of the feed reverse lever is set
at an appropriate tension for easy and comfortable
sewing operation.
If it is necessary to adjust the feed reverse
lever spring tension, tip machine back and loosen
feed reverse lever spring retainer screw Y3
holding the spring retainer 23 on the machine leg.
Move spring retainer 23 up or down, as required,
and firmly tighten screw Y3.
The lighter the tension, the easier it is to
operate the feed reverse lever, however the ten-
sion should be set a little heavier for maximum
stitch length and high speed sewing.
Normally, the machine is adjusted to sew a
maximum stitch length of 4.2 mm. This however,
can be changed to 5.1 mm (5 S.P.I.) is desired,
by turning over the feed regulating dial stopper
C4 on the underside of the feed reverse lever, as
shown in Fig. 10.
CAUTION: MAKE SURE the feed dog clears the front and rear edges of the
throat plate slots when maximum stitch length is changed to 5.1 mm.
TO TIME THE FEED
Before the machine leaves
the factory, the fear and feed
lifting eccentric is set for
average sewing conditions;
having the timing screw (screw
M which appears immediately
after set screw N, Fig. ll,
when feed eccentric is rotated
toward the operator) align on
the timing mark provided for
it on the arm shaft.
The timing screw M, Fig.
ll, on the feed and feed lift-
ing eccentric should be se-
curely tightened after it has
been aligned on the timing mark on the arm shaft. The set screw M should also
be securely tightened.
If for any reason, it is necessary to alter the timing of feed and feed
lifting eccentric, the eccentric should be adjusted and locked in desired
setting with the timing screw M and the set screw N.
Fig. 11
N
M
Y3
Z3
Fig. 10
C4