Singer Centurion 121D200A User manual

1
SERVICE MANUAL
SINGER
Sewing Machine
121D200A
Copyright ® 1976 The Singer Company
Aii Rights Reserved Throughout the World
*A Trademark of THE SiNGER COMPANY
Form 21624 (876) Printed In U.S.A.
From the library of: Superior Sewing Machine & Supply LLC

L.
LUBRICATION
Moving parts have either permanently sealed pre-lubricated ball or needle bearings or
oil Impregnated bushings which require no manual lubrication. The following exceptions
are:
HOOK
An oil reservoir supplies oil to the sewing hook race and Is filled through the oil cup as
shown, until the word "FULL" Is seen In the Indicator window.
Check oil level at Indicator window dally before starting machine. As oil level decreases,
red arrow will appear (Fig. A).
0
Red Arrow Empty ( H-
FIG. A
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TO TEST HOOK LUBRICATION
Thread machine and sew 3 yards of scrap material. Pay no attention to stitch quality or
amount of oil at this time. Remove material and bed slide. Run machine approximately
one minute to establish a,uniform oil flow. Without stopping machine, hold a piece of
paper in place under hook for 10 seconds. Remove paper and compare oil pattern with
Fig. B for proper oil flow.
••• , " • # • ♦ •
FIG. B
If there is no trace of oil or an excess, adjustment should be made with the oil metering
screw, in order to gain access to oil metering screw, the hook should be in position as
shown in Fig. C. Turn oil metering screw clockwise for more oil and counterclockwise for
less (Fig. D). Normal setting is made by turning metering screw to maximum in position
and backing out 2-1/2 turns. Less than 2-112 turns may be required for long continuous
runs.
FIG. C
Oil Metering
Screw
Hook Shaft
Bushing
Oil
Filter
More Oil
FIG. D
Oil Metering
Screw
Less Oil
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Ifoil flow is not satisfactory, remove hook assembly and oil filter. Check filter. Oil wick
should be replaced whenever it has become clogged with lint or dirt. An excess of oil
sometimes indicates that the filter wick has become detached from the screw or the
screw is not securely tightened. Inspect all oil passages to see they have not become
clogged.
Oil Filter
(S)
Hook Assembly
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MACHINE THREADING
1. Move needle to highest point
2. Lead thread from thread stand through thread post atop machine arm
3. Through 3 eyelets of thread guard
4. Units with U.T.T., through pretensioner
5. Down through thread retainer
6. Into and around tension assembly
7. Over check spring and under slack thread regulator
8. Up to and through thread retainer and take-up eyelet
9. Down through thread retainers (2)
10. Through needle bar thread guide
11. Through needle eye from left to right
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STITCH LENGTH
The stitch length can be regulated while the machine \s^'m operation. To obtain the
desired stitch length In forward feed, turn regulating thumb screw on oil pan "In" (coun
terclockwise) for more stitches per Inch, and "out" (clockwise) for less (Fig. B).
To adjust the stitch length for reverse feed. It Is necessary that the reverse stopping
block be properly positioned. This Is done by loosening the lock screw In the stopping
block and sliding the slide block up or down to the desired stitch length. The locking
screw must then be retlghtened (Fig. A).
Forward
I
Reverse
-0
Locking Screw
FIG. A
PRESSER FOOT PRESSURE
The pressure on the material should be as light as
possible while still sufficient to ensure correct feed
ing. There are two regulating screws that control the
presser foot pressure. One atop the arm and one at
the rear of the machine. The one atop the arm Is the
major control, normally adjusted prior to long pro
duction runs or new applications. For day-by-day
casual adjustments, the regulating screw at the rear
Is used, screwing In for less pressure and unscrew
ing for more pressure. When this rear screw Is
unscrewed all the way out. It disengages; only then
can the top screw be applied, and It serves as the
sole control until the rear screw Is again turned In
ward (Fig. C).
Less
FIG. B
Regulating Screw B when
Screw A is Disengaged
Regulating
Screw A
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HOOK TIMING
Proper clearance between needle and hook point, re
quires that the point of the hook shouid pass the nee-
die as closely as possible without striking or deflect
ing it. There shouid be .003 - .005 clearance bet
ween the two (Fig. A).
To adjust clearance, loosen bushing set screw (Fig.
B). With screwdriver placed as shown move entire
hook and bushing (Fig. C). Tighten bushing set
screw.
Hook Bushing
Set Screw
FIG. B
Insure that the needle guard prevents the
needle from contacting the hook point at
any time. If large needles are to be used it
may be necessary to string the needle
guard back to allow hook point closer to
needle (Fig. D).
6
.003 • .005
Rat of
Hook Point
To Needle
FIG. A
FIG. C
Needle Guard
FIG. D
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HOOK TIMING CONT'D
Reset position finger so there is .018 - .022
thread clearance between finger and
basket (Fig. E).
^.018" - .022"
FIG. E
Loosen hook set screws. Turn hand wheel in direction of rotation until needle bar is on
the rise stroke, and the lower mark is aligned with the needle bar height indicator. Set
hook point to the center line of the needle (Fig. F). Tighten hook set screws.
Needle Bar
Height indicator
FIG. F
Hook Point to
Centeriine of Needle
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TIMING FEED LIFTING SHAFT TO ARM SHAFT
Manually rotate arm shaft until timing mark
on counterbalance aligns with timing mark
on take-up stud connecting link (Fig. A).
0
Timing Marks
FIG. A
Loosen bed shaft timing belt pulley set screws (Fig. B). Hold pulley stationary and rotate
bed shaft until timing mark at feed bar end of shaft aligns with timing mark on casting
(Fig. C). Timing marks alignment in Fig. A and Fig. C must occur simultaneously. Tighten
pulley set screws.
Set ®
Screw (2)
ry
n
FIG. B
TO
]
Q) ®
Timing Marks
FIG. C
8
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FEED DOG SETTING
Centrally locate feed dog in throat plate slots. Feed dog must not make contact with
throat plate, as noted. Align by loosening feed dog screws. Then retighten screws Fig. A.
Feed Dog
No Contact
FIG. A
LATERAL SETTING: Loosen pinch screw infeed bar crank (Fig. B).Shift feed bar as re
quired. Ensure that feed bar does not contact position finger.Tighten pinch screw and
check axial play at pendant link. Adjust feed lifting shaft to minimize play.
Leveling
Eccentric
Feed Bar Crank
Pinch Screw
Height Eccentric
and
Locking Nut
FIG. B
9
Leveling Eccentric
Set Screws
From the library of: Superior Sewing Machine & Supply LLC