JUKI LK-980 Series Quick start guide

No. IV-8-1
1983.8
lIUKI
LK-980
Series
High Speed 1-Needle, Cylinder Bed, Lockstitch
Bar Tacking Industrial Sewing Machine
ENGINEER'S MANUAL
TOKYO JOKI INOOSTRIAL CO., LTD
FOREIGN TRADE BUSINESS DIV.
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INTRODUCTION
This booklet consists mainly of 3parts, the first part is for the "Standard Adjust
ments" covering the basic adjustments and their directions, the second part is for
elimination of mechanical troubles and the third part is for the subclass models of the
LK-980 series.
We hope all service engineers will read and study carefully the first part "Standard
Adjustment."
The "Standard Adjustment" explained in simple terms with illustrations will
facilitate quick access to the practical services for service engineers in the field. The
columns "Possible problems or phenomena caused by improper adjustments" and
"Corrections" are added for inexperienced service engineers.
To make optimum use of this booklet, we advise you to refer to "PARTS BOOK
for the LK-980 series."
If the brief descriptions given in "Standard Adjustment" are not enough, refer to
the relative item for further details.
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CONTENTS
I. STANDARD ADJUSTMENTS 1
II. MEASURES TO ELIMINATE STITCHING FAILURES 12
(1) Thread escape 12
(2) Thread breakage 14
(3) Thread trimming failure 17
(4) Needle breakage 18
(5) Precautions when sewingsynthetic materials 19
(6) Loose stitching 19
III. THINGS TO BE NOTED WHEN DISASSEMBLING AND ASSEMBLING THE MACHINE 20
(1) How to remove the shuttle driver shaft 20
(2) How to remove the main shaft 20
IV. ELIMINATION OF EXCESSIVE PLAY 20
(1) Excessiveplay in the main shaft 20
(2) Excessive play of the feed cam driving worm against the feed cam driving worm wheel 21
(3) Excessive play
of the feed cam roller 21
(4) Excessiveplay in the shuttle driver shaft 21
(5) Cork linings
ia the clutch components 21
V. DETAILS OF ADJUSTMENT 22
(1) Adjustment for starting and stopping 22
(2) Adjustment of the pedal pressure decreasing unit 27
(3) Adjustment of the thread trimmer components 29
(4) Feed cam components 30
(5) Adjustment
of the shuttle race 31
(6) Height
of the work clamp foot 32
(7) Height
of the wiper 32
(8) Checking the safety device 32
(9) Adjustment of the bobbin winder 33
(10) Tension
of the V-belt 33
(11) Silicone oil lubricator 33
(12) Application of "lock-tight" paint 33
(13) Greasing 34
(14) Replacement parts 36
VI. HINTS ON SUBCLASS MODEL MODIFICATIONS 38
VII. UTILIZATION OF SPECIAL COMPONENTS 41
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I. STANDARD ADJUSTMENTS
Standard adjustments
(1) Needle and sewing hook
1) Height of the needle bar
When the needle bar has reached Its lowest position, the upper
engraved line on the needle bar must align with the bottom
end of the needle bar bushing (lower).
2) Shuttle
With the above needle bar position, the pointed end of the
shuttle must align with the needle center.
3) Clearance between the needle surface and the shuttle must be
0.05 to 0.1 mm.
4) There must be no clearance between the needle and the shuttle
driver. The top end of the shuttle driver prevents the needle
from bending as shown In Fig. 1-b.
5) Clearance between the top end of the shuttle driver and the
shuttle must be 0.3 to 0.5 mm (about 1/64").
When the needle has
reached its lowest
position.
When the needle thread
is taken up by the
shuttle.
Upper engarved
line
Lower engraved
line
Fig. 1-a
Fig. 1-b
0.05—0. Inim
Fig. 1-c
Onim
Shuttle driver
Fig. 1-d
Note:
Adjustments of "Height of the needle bar" and "shuttle" may vary
In some subclass models
(2) Feed cam
Adjust the cam so that the cloth feed motion Is completed when
the needle point has come down 7 to 10 mm (9/32" to 25/64")
above the throat plate surface.
- 1 -
7—lOram
t
Fig. 2
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Possibletroubles and phenomena caused by
Improper adjustments
(1) When sewing materials whichtend to flutter while
being stitched, set the needle bar slightly lower
than the standard height.
When sewing a heavy-weight material, providing
it isnot of a type that tends to flutter, set the
needle bar slightly higher than the standard
height.
(2) When using a synthetic or soft and thin thread
(for example, cotton thread #80), in order to
prevent it from falling down and snagging, do not
allow it to form a large loop.
(3) If the shuttle comes closer to the needle than
0.05 mm, they may touch and scratch each other.
The scratcheson their surfaceswill damage a thin
or synthetic thread.
If the clearance is greater than 0.1 mm stitch-
skipping will result.
(4) If
the shuttle driver dosen't come into close
contact with the needle, the needle will bend
backwards. The bent needle will hit the blade
point of the shuttle scratching them both. If this
happens the thread is likely to be broken or torn
by these scratched surfaces.
If the needle isonly slightlybent, stitching will not be
affected. If, however, it isbent too much, it may
cause stitch-skipping.
(5) If the clearance between the shuttle driver and
the shuttle isgreater than 0.3 to 0.5 mm (about
1/64"), a noisewill result during operation. If it
is too small, a thick thread may fail to be drawn
out resulting in formation of a loose stitch.
If the needle point height is set closer to 7 mm
(9/32"), the stitch will be tightly formed. Whenthe
needle point height is set closer to 10 mm (25/64"),
it prevents synthetic needle thread from coming out
on the surface of the material and forming an idle
loop on the first stitch. (No special care is needed for
sewing heavy-weight material)
Corrections
See "3. Needle Bar Components" in the Parts Book.
Remove
the face plate and adjust the needle bar
height by loosening screw (SS-6090670-TP) of needle
bar connection.
See "5. Shuttle Driver Shaft Components" in the
Parts Book.
Loosen screw (SS-6121212-TP) and adjust the shuttle
driver.
See "5. Shuttle Driver Shaft Components" in the
Parts Book.
Loosen screw (SS-6151220-SP) to set free shuttle
race and adjust the shuttle race position in the axial
direction by turning shuttle raceadjustingshaft
(B1819-280-000)
Loosen screw (SS-6121212-TP) and adjust shuttle
driver in the axial direction by taking care not to turn
the shuttle driver in the direction of rotation. If you
mistakenly allow the shuttle driver to rotate, readjust
the shuttle according to 2).
Although eachend of the shuttledriverishardened,
you can bend it at the middle point when adjusting
the clearance at the shuttle. Remove the shuttle from
the shaft for bending, otherwise the shuttle mayshake
on the shaft when rotating. Alsotake care to keep
point (3) at an equal distancefrom each lipof the
shuttle, in order to let the thread passthrough
smoothly. It is advisable to tap the shuttle at the
point © .
Fig. 1-e
See "6. Feed Cam Components" in the Parts Book.
Loosen nut (NS-6360621-SN) and also loosen feed
cam position stud (B2207-280-000). Now the feed
cam can be freely adjusted in the normal direction
of rotation.
(Note) (Once you have adjusted the feed cam position,
you should not change it afterwards. If changed,
you must readjust the thread tension release
components and the stop-motion regulating
cam (Refer to the relevant paragraphs in this
Manual.)
- 2 -
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Standard adjustments
(IMPORTANT) The following adjustment, from (3) to (7), must without
exception, be made in the stipulated order.
(3) Position of the stop-motion hook
During low-speed rotation, the white line No. 2 on the stop-
motion hook must coincide with the periphery of the brake
ring.
White line No
Stop-motion regulat
ing cam roller
Fig. 3-a
Brake ring
Fig. 3-b
(4) Position of the stop-motion regulating cam
(to start stitching)
Align the top surface of the stop-motion hook with the stop-
motion regulating .cam at point ® and fix the stop-motion
regulating cam by pressing the cam roller againstpoint ® ,
Stop-motion cam
Stop-motion notch
Fig. 4-a
(5) Stop-motion notch
The timing to let the roller drop and rest in the stop-motion cam
after the last stitch is sewn is determined by the position of the
stop-motion notch.
Provide the stop-motion notch with a proper position by moving
it up or down, according to the sewing speeds as listed below,
when the last stitch is sewn and the top edge of the stop-motion
hook touches the stop-motion cam.
Position of the stop-motion hook
At 1,700 s.p.m. Center of the 2nd screw.
At 2,000 s.p.m. Between the 1st and the 2nd screws.
At 2,200 s.p.m. Center of the 1st screw.
(6) Drivingpulley pressing plate
The driving pulley pressing plate must be adjusted so that
the machine starts running when the white line No. 1
coincides with the periphery of the brake ring.
- 3 -
Stop-motion hook
Cam fixing nut
Stop-motion
regulating-
cam roller ^Fig.
4-b
Stop-motion regulating cam
Fixing bolt
Stop-motion cam
2nd
screw
White line No. 1
Driving pulley
pressing plate
1st
Stop-motion Fig. 5
hook
In case of 1,700 s.p.m.
Brake ring
Adjusting bolt
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Possible troubles and phenomena caused by
improper adjustments
If white line No. 2 enters into the periphery too
far, the stop-motion hook may hit the regulating
cam. This will cause noise and the low speed cork
ring will slip
due to insufficient engagement.
If white line No. 2 is too far out from the
periphery, the motion of the thread trimmer cam
roller may be hindered, resulting in thread
trimming failure.
When the motor pulley is changed to vary the sewing
speed, this position must be corrected at the same
time.
(Note) The degree of stop-motion shock depends also
on the position of the stop-motion notch.
If the sewing machine carries an excessive
rotational torque to reduce its sewing speed
especially in a cold season, shift the notch
position counterclockwise along the circum
ference to increase the counteraction.
If the machine starts running too quickly, the
speed reduction ball bearing will slip and make a
noise when the machine starts or stops.
If the machine starts running too slowly, the start
pedal may become heavy to operate and the
clutch may fail to engage firmly, resulting in
slipping.
Do not turn too much to the left the adjusting
bolt which fastens the driving pulley pressing
plate. Stop the machine, turn by hand the driving
pulley and ensure that It does not rotate the low
speed cork ring and the brake cork ring. If they
are rotated, the friction surfaces in the brake
components may wear away during operation.
Corrections
Loosen nut (NS-6150430-SP) and adjust the position
of stop-motion regulating cam shaft (B2614-280-000)
in the direction shown by the arrow.
Since this nut tends to loosen during operation,
tighten it securely after adjustment.
See "9. Stop-motion Mechanism Components" in the
Parts Book.
Depressthe start pedal and adjust point ® . Loosen
3bolts (SS-9151120-CP) and adjust stop-motion
regulating cam (B2612-980-000). Loosen the cam
fixing nut (NS-6361040-SP) and set cam (B2612-980-
000) to point (B) . (Point ® can be seen through
an opening in the brake ring)
Adjust the position of stop-motion notch (D2630-
M8W-B00) as shown in Fig. 4-b.
Adjust the position of driving pulley pressing plate
(82611-980-000) by tightening or loosening bolt
(88-9151420-TP).
Adjust driving pulley pressing plate (82611-980-000)
so that the low speed cork ring (see Fig. 7-b) starts
lightly engaging with the driving pulley when the
stop-motion hook moves into the periphery of
the stop-motion cam to start sewing. (See Fig.
4-b)
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Standard adjustments
(7) Stop-motion connecting pin
When the start pedal is depressed to restart, the brake ring
must move away by 0.1 to 0.5 mm (about 1/64").
(8) Positionof the safety adjustingplate
When the work clamp foot lifting lever is
down in the stop-motion position the
safety adjusting plate touches at point (S)
When the work clamp foot lifting lever is
up, the safety adjusting plate has a
clearance of 0.3 mm.
Low speed cork ring
Brake cork ring
(9) Position of the shuttle race spring
1) Crosswise position :
The center of
the slit must align with the needle point.
2) Lengthwise position :
The edges ® of the spring must align with the rear face of
the needle.
- 5 -
Fig. 8-a
Stop-motion connecting pin
/
Fig. 7-a
Driving pulley
f 0.1 to 0.5mm
^ (about 1/64")
Brake ring
Fig. 7-b
Fig. 8-b Fig. 8-b
Fig. 9
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Possible troubles and phenomena caused by
improper adjustments
If the brake ring goes too far, it will make the
return of the stop-motion lever incomplete result
ing in an incomplete stop-motion. Also, it may
fail to release the safety device which locks the
work clamp foot.
If the brake ring does not go far enough, stop-
motion shock will be increased. In this case, the
stop-motion ball may be damaged resulting in
noise when the sewing speed is changed from low
to high speed.
With a properly adjusted machine, the work
clamp foot will perform normal up-and-down
motion and the brake cork ring will momentarily
rotate in the reverse direction just before stop-
motion is completed.
If there is any clearance at point ® , the wiper
•will move too early and hit the needle point.
If the clearance is smaller than 0.3 mm, the motion
to be performed by the safety adjusting plate will
be hindered.
If it is too much, the work clamp foot may
accidentally go up during operation.
If the spring does not allow the needle to pass through
the above-mentioned point, the needle thread will
snag in the sewing hook. If the needle drops too far
to the rear, the moving knife may fail to hook the
needle thread.
Corrections
See "2. Main Shaft Components" in the Parts Book.
Loosen screw (SS-6151920-TP) and adjust the
position of the "stop-motion" connecting pin
(82623-980-000) in the direction shown by the
arrow. After adjustment, check the following point.
Bring it into the starting position by turning driving
pulley and make sure that brake cork ring idles while
the main shaft rotatesfrom 100to 200° to change
the sewing speed from high to low.
(However, when sewing many stitches, the idling
angle maybe in excess of 200°. When sewing canton
crepe or other extra-heavy materials, the angle may
be reduced down to 100°).
See "8. Pedal Pressure Decreasing Unit Components"
in the Parts Book.
Adjust the position of the safety adjusting plate by
loosening screws (SS-6111010-TP).
See "5. Shuttle Driver Shaft Components" in the
Parts Book.
Remove the feed plate and the needle plate and
adjust the position of shuttle race spring by
loosening 2screws (SS-6060410-TP).
- 6 -
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Standard adjustments
(10) Thread trimmer
1) When the machine is in stop-motion, the distance from the
thread hooking point of the moving knife to the nearest end of
the needle hole in the needle plate must be 1.5 mm (1/16").
2) The distance from the counter knife edge to the needle hole
guide on the needle plate must be 0.5 mm (1/64").
(11) Position of the work damp foot
1) Large bar tacking machine (42 stitches) :
The 26th stitch must be aligned with the center slit in the
work clamp foot.
2) Large bar tacking machine (28 stitches) :
The 18th stitch must be aligned with the center slit in the
work clamp foot.
Fig. 10
.Center slit in the work clamp foot
[26th stitch of 42 stitches
bar tack machine
fISth stitch of 28 stitches
bar tack machine
Fig. 11
Z
I wm%m i)][i
(12) Position of the wiper
The wiper clearance at the needle point must be 1.5 mm (1/16")
when the wiper passes under the needle point.
- 7 -
a
Fig. 12-a
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Possible troubles and phenomena caused by
Improper adjustments
If the needle thread being released from the hook
bladeat the laststitch istoo tight, add a slightdis
tance to the stipulated "1.5 mm". Whenusinga thick
thread, slightly reduce the "1.5 mm" distance. As the
"0.5 mm" distance is increased, the bobbin thread
length from
the bobbin case pawl will become shorter
and
the bobbin thread will skip the first stitch.
If not correctly adjusted, it will make the buttonhole
positioning work harder.
If the clearance is not enough, the wiper may hit and
break the needle point.
If the clearance is too much, the needle clamp screw
will touch the wiper.
Corrections
See "3. Needle Bar Components" in the Parts Book.
Loosen screw (SS-7110740-TP) and adjust the
position of the moving knife driving lever (B2415-
280-0A0) to front or rear.
See "6. Feed Cam Components" in the Parts Book.
Loosen nut (NS-6660511-SP) which fastens feed
cam roller shaft and adjust the position.
See also page 30.
See "4. Thread Tension Release Components" in the
Parts Book.
Loosen screw (SS-7110840-SP) of wiper installing
plate (B2102-280-000) and adjust the height of the
wiper. Also refer to the relevant paragraph on page 32.
Fig. 12-b
Stop-motion hook
Stop-motion cam
(Note) The stop-motion cam can move freely within
the limit of clearance (a) after the stop-motion
mechanism activates. But, when adjusting,
never fail to push the stop-motion hook
against the face ® .
- 8 -
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Standard adjustments
^13) Timing of thread tension release
1) When the machine is in stop-motion position, the tension
release link latch must rest on top of the tension release
link tripping segment,
2) When, on completion of the last stitch, the highest point of
the ascending thread take-up lever has reached the level
shown by a white dot on the machine arm, tension disc
No, 2 must start releasing the thread.
3) While stitches are being made, the tip of the tension release
link latch must not touch the periphery of the rotating feed
cam.
Tension release lever
Tension release link latch
r
Thread take-up
ilever
1
Tension release linkj
tripping segment |
Fig, 13-a
(14) V-belt tension
When the middle point of the V-belt is pressed with the finger
(pressure of about 1 kg), it should have a slack of 10 to 15 mm
in depth (25/64" to 19/32"),
(15) Position of the bobbin winder
When the bobbin winder is not operated, the bobbin winder
wheel must be kept apart from the V-belt so that the periphery
of the wheel rim is at the level of the edge of the V-belt,
- 9 -
White dot
Fig. 13-b
Fig. 15-a
Clearance
Fig, 13-c
A slack of 10 to 15 mm
(25/64" to 19/32")
deep with a pressure of
about 1 kg
Fig, 14
V-belt
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Possibletroubles and phenomena caused by
improper adjustments
1) If the tension release link latch is far below the top
of the tripping segment, the first stitch may
become loose. If it goes up too high above and
runs through the segment, it will fail to perform
the action explained in 2).
2) If the thread tension release system works too
quickly, the length of trimmed thread may become
uneven and long.
If it works too slowly, the length of trimmed
tjiread may become short and may slip out of the
needle eye.
Hints on adjustment
Needle thread Tension release lever
Too long
Turn up
Uneven Turn up
Too short Turn down
Broken or slipping
out
Turn down
3) If the tension release link latch touches the
periphery of the feed cam during operation, it will
be worn down causing variation in the thread
release timing, resulting in thread trimming failure.
• If the V-belt tension is too high, the driving pulley
will not slip correctly and the stop-motion shock
will be considerably increased.
• If
the V-belt tension is too low, the sewing speed
will decrease and the machine will stop a little
before the correct stop-motion position.
(Caution) Be sure to position the pressure decreas
ing belt of the tension pulley.
If the belt tension is too low, the unit
may fail to work properly.
If the bobbin winder wheel is positioned too close to
the V-belt, it may be accidentally turned or rubbed by
the V-belt.
If it is too far from the V-belt, it may fail to wind the
bobbin.
Fig. 15b Bobbin winder base
- 10
Corrections
See "4. Thread Tension Release Components" in the
Parts Book.
Loosen screws (SS-7090520-TP) and adjust tension
release link tripping segment (82304-980-000).
Next to thread guide No. 1, there isan adjusting hole
for hingescrew.(SD-0500481-TP) to set tension release
release link latch.
Insert ascrew driver into the adjusting hole and
slightlyloosenthe hinge screw. You willthen be able
to adjust the timingof the thread release by changing
the positionof the tension release lever (82308-980-
OAO) according to the directions given above.
Adjust the tension release link latch by turning screw
(SS-8151150-TP).
See "11. Table Components" in the Parts Book.
Adjust the tension of V-belt by changing the height
of motor base assembly.
See "3. Needle Bar Components" in the Parts Book.
1) Adjust the position of bobbin winder base by
loosening screws (SS-7151210-SP).
2) If bobbin winder spindle is rotated while the
bobbin winder is not in use, loosen screw
(SS-7110510-SP) on pressure plate and push
out bobbin winder brake (83209-280-000).
3) If the bobbin winder fails to wind the thread
evenly, carefully correct the angle of bobbin
winder base (83201-280-000) by using a pair
of pliers.
Fig.
15-c
Bend it to the left
.Bend it to the right
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(16) Rotating the machine by hand
You will not be able to depress the start pedal, even if you try to rotate the machine by hand. Detach spring
(B2629-980-000) (see
"9. Stop-motion MechanismComponents" in the Parts Book) from the upper anchor, rotate
driving pulley 2 or 3 turns to bring down the work clamp foot and depress the start pedal.
(17) Motor pulley and driving belt
Even though adequate tension is produced by the pair of belts as listed below, use the tension pulley (B7805-980-
OAO) (see Parts Book p. 19) as well.
Take care not to allow the belt tension to change during rotation, as change
of tension would seriously impair
performance.
The power frequency and rate of revolution are inscribed on each pulley.
Frequency Sewing
speed
(s.p.m.)
Maximum dia. of
motor pulley
(0, mm) Driving belt Pressure decreasing
belt
50 Hz
2200 112.5 B7101980000 48" MTJVM004800 35" MTJVM003500
2000 99.5
B710198000B 47" MTJVM004700 34"
MTJVM003400
1700 87.5 B710198000C 46" MTJVM004600
34"
MTJVM003400
1400 73.0 B710198000D 46" MTJVM004600 35 "
MTJVM003500
60 Hz
2200
94.6 B7102980000
47"
MTJVM004700
34" MTJVM003400
2000
84.0
B710298000B 46" MTJVM004600 34" MTJVM003400
1700 74.0 B710298000C 46" MTJVM004600 35" MTJVM003500
1400
59.5 B710298000D
45 " MTJVM004500 35 "
MTJVM003500
(Note) For a sewing speed of less than 1,400 s.p.m., stop-motion regulating cam (D1214-M7X-C00) specially designed
for low speed operation must be used.
For operation at a speed of 1,400 s.p.m. with power frequency of 60 Hz, idler pulley (B7801-280-0A0) must be
used.
(18) Needle sizes and needle plate needle hole guides suitable for different types of material
Material type
Needle size
Needle plate needle hole guide
Garments
Fine DPx5 #11 D2426-282-C00 Knits, tricot, underwears
Synthetic
DPx5 #14
(Super needle)
B2426-280-000
Small, large and
buttonhole bar
tacking
D2426-284-M00
Shape bar tacking
Men's suits, Ladies' suits.
Casual wears
Standard DPx5 #16
Heavy-weight DPx5 #18 Working wear. Coat
Extra-heavy
DPx5 #19~#21
♦DPxl7 #r8~#21
B2426-280-00B
Jeans, heavy winter wear
(Note) Do not use needle LQ x 5 whichhas been installedin the conventional model LK-232.
(*) When usinga DPx 17 needlefor sewing heavy-weight materials,use the following parts at the sametime;
Needle bar D1401-L7V-V00
Needle bar thread guide D1405-L7A-M00
For sewing heavy denims, refer to the table in paragraph (4) Use of the Special Parts, page 42, "When a thick
needle is used" and "When a thick thread is used."
.(19) Other possible troubles
1) If you depress the start pedal rapidly, the machine may fail to start.
Depress the start pedal slowly so that the work clampfoot comes downto release the machine fromthe safety
device.
2) When the machinestops after the needle has come down to sewthe first stitch;
Depress the* start pedal fully downwards.
If this trouble occurs frequently, adjust the stop-motionregulating camby moving it slightly in the directionof
rotation. (Reduce the stop-motion shock by referring to (11) and (12).)
3) When operating the machine at a speed of 2,200 s.p.m. or usinga thick thread, manually apply a little more
lubricating oil to the shuttle race.
- 11 -
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(20) Installing method of LK-980 driving pulley pressing plate
1. Mounting the drivingpulley pressingplate in the following order (Fig. A):
1) Unscrew the hezagonal head screw (T) and screw (3) , remove the washer and remove the previously
installed grease box .(Removed hexagonal head screw and the washer are to be disposed of.)
2) Apply grease to the ball (A) and thetop portion (S) ofthe new driving pulley pressing plate (small) 0 .
3) Fix the new greasebox and drivingpulley pressingplate (small with the new screw (hinge screw SD-0800402-TP
(T) and then mount the combination to the stop-motion lever (7) and fasten it with screws 0 and (3).
2. Adjustmentof the driving pulley pressing plate(Fig. A, B)
1) Turn the driving pulley (© by hand inthe direction ofan arrow (•«-) given in Fig. A when theouter periphery
of the brake ring 0 fits the first white line of stop-motion hook (9), adjust the screw ® sothatthe clutch
starts operation and the machine begins running, adjust the greasebox in the direction of (**) in Fig. B and then
fasten it with the nut. (Note that timing after variesif the nut is fastened.)
2) Ensure always thatthe slow speed cork ring (Q) and brake cork ring (Q) don't rotate during operation ofthe
brake ring while the machine is suspended.
Readjust the screw (6) since it causes wearing accidents ofthe reduction gear ifthe slow speed cork ring (Q)
and brake cork ring (Ql are rotating.
8 10
First white line
Driving pulley
Fig. A Fig. B
- 12 -
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II. MEASURES TO ELIMINATE STITCHING FAILURES
This chapter covers stitching failures and theircorrective measures, e.g.thread escape, thread breakage, stitch-skipping,
needle breakage, thread trimmer failure and related problems.
(1) Thread escape
Phenomenon The machine fails to form the first, secondor third stitchesand the thread slipsout of the
needle eye.
Possiblecauses ^The first stitch wasskipped.
•The thread left in the needle eye before starting was too short.
•The thread take-up spring was not properly adjusted.
•The bobbin thread was too short.
Corrective measures
1) To preventthe firststitch from being skipped
A. Check the relative position of the shuttle to the
needle.
Readjust it, if necessary.
B. Correct the clearance between the needle and the
shuttle. Set the shuttle race free by loosening the
setscrew. Reduce the clearance to 0.05 to 0.1 mm
by tuming the shuttle race adjusting shaft. Take
care not to make the clearance smaller than stipu
lated, or the two may touch, which would cause
wear. (Fig. 16)
C. Allow the shuttle to rotate smoothly.
Provide the shuttle with a lapping finish so
that it
rotates smoothly in the shuttle race. Thoroughly
clean the inside surface of the shuttle race and
remove all fibrous dust and lints.
D. Prevent the material under the work clamp foot
from fluttering. A special set of work clamp com
ponents by which the material can be securely
clamped in a "U" shape (as shown in Fig. 17)
preventsthe material from fluttering while stitching.
Large-size bar tacking components designed for knit
goods are available;
Feed plate B2519-280-00B
Work clamp foot (right) B2551-280-00B
Workclamp foot (left) B2552-280-00B
E. Check if the feed cam is synchronized with the
needle.
When the needle starts stitching the material, the
feed cam must stop feeding the material.
If the needle is carried away by the material, you
must loosen the feed cam positioningpin and adjust
the feed cam timing. After adjusting the feed cam,
correct the positions of the stop-motion regulating
cam and the tension release link tripping segment
accordingly. (Fig. 18)
- 13
Cam fixing nut
Setscrew
Shuttle race adjusting shaft
1
Fig. 16
Material Work clamp foot
Feed plate
Tension release link
tripping segment
Feed cam positioning pin
at>
Fig. 17
Stop-motion
regulating cam
First stitch positioning
hole
Fig. 18
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2) Adjust the machine to leave a longer needle thread
after trimming.
If the needle thread left in the needle eye after trim
ming is too short, it will slip out of the needle while
the first stitch is being formed.
A. The standard length of the needle thread left in the
needle after trimming is 35 to 40 mm (1-3/8" to
1-37/64").
B. If the thread tension is releasedtoo late, the remain
ing needle thread will become too short and may
spring out of the needle. Correct the thread release
timing, by means of the tension release lever. If the
timing is too fast, the thread length will be uneven
or too long (See standard adjustment (13)).
C. If the tension disc No. 1 istoo tight, the thread left
in the needle eye wUl become too short.
D. If the counter knife position is too high, it will cut
the thread before the moving knife arrives in the
cutting position. If this happens neither the needle
and bobbin thread lengths will be enouth to start
the following stitch. The bottom surface of the
counter knife must be positioned 0.1 to 0.15 mm
lower than that of the needle plate needle hole
guide (Fig. 20).
E. As mentioned in the standard adjustment (10)
"Thread Trimmer", when the machine is in the
stop-motion position, the thread hooking point of
the moving knife must be 1.5 mm (1/16") away
from the nearest end of the needle hole in the
needle plate. If the distance is greater than 1.5 mm
(1/16"), a shorter needle thread will be left in the
needle.
3) To adjustthe thread take-up spring(Fig. 21)
A. If the stroke of the thread take-up spring is too
great, it may draw in the needle thread immediately
after the thread is cut. Thus, the thread left in the
needle eye will be too short and will slip out.
B. To reduce the stroke of the thread take-up spring,
loosen the bolt to set tension controller No. 2 and
turn the entire tension controller in the anticlock
wise direction.
C. To increase the stroke of the thread take-up spring,
loosen the setscrew of the tension post, insert a
screw driver blade into the tension controller in the
way shown by the arrow and turn it anticlockwise.
D. Tighten
the setscrew and bolt of tension controller
No. 2 securely. If they are not firmly fixed in posi
tion, the tension disc will fail to release the thread
and allow it to jump up out of the needle eye.
(Note) When the tension discreleases the thread, make sure
that the tension release pin meets the tension release
rod at the rising part of the tension release bar. If
they meet at the upper straight part, the tension
Release bar may fail to return. (Fig. 22)
- 14 -
Needle thread slips out
Setscrew
Fig. 19
Needle plate needle hole guide
A
Counter knife
Fig. 20
: Bolt
Fig. 21
Tension release bar
Rising part
Fig. 22
From the library of: Superior Sewing Machine & Supply LLC

4) Bobbin thread is too short.
A. If the bobbin thread extending from the top end of
the bobbin case finger is less than22 mm(7/8"), the
machine may fail to form stitches (Fig. 23). Provide
a little more distance between the counter knife and
the needleplate needlehole guide.
B. If the vertical distance between the needle plate
needle hole guide and the counter knife is too
much, the thread may come into contact with the
counter knife and may be broken.
C. If there is any burr or scratch on the shuttle surface
race spring at point (§) , it may cut or break the
bobbin thread. Make part (g) smooth by the use of
abrasives. (Fig. 24)
D. In order to prevent the bobbin thread from com-
ming out due to idle spinning of the bobbin, use
both the bobbin and bobbin case specially designed
for the LK-980 model.
(2) Thread breakage
(1) Thread breakage when sewing
Phenomenon Either the bobbin or the needle thread is acci
dentally cut while stitching.
Possible causes •The shuttle is scratched.
•The thread is snagged in the shuttle.
•The shuttle driver is scratched.
•The shuttle driver is too close to the shuttle.
•The needle plate needle hole guide is scratched.
•The needle is touching the work clamp foot.
•The needle is scratched.
•The needle thread tension at the time of
piercing the material is too high.
•Timing of the feed cam motion is not correct.
Corrective measures
1) Scratched shuttle (Fig. 25)
A. If the needle hits the shuttle, the blade point ® will be worn to a
knife edge. Carefully polish it with an oilstone and abrasivesand keep
it slightly away from the needle point. However, do not push it back
too far from the needle to prevent stitch-skipping. Also, take care not
to provide too much clearance between the front face of the shuttle
driver and the needle when the needle bar has reached its lowest
position, in order to prevent the needld from bending. In such a case,
adjust the shuttle driver position in
the axial direction, so that it
protects the needle. When the blade point of the shuttle has been
seriously damaged, also check to see if the shadowed area (Fig. 26) on
the rear face of the shuttle race is of the correct shape as illustrated. If
not, correct the shape with an oilstone.
B. If the needle is bent or broken, the shuttle may be damagedat point
® . This scratch may damage or break the needle thread when
releasing. This is the most frequent cause of this type of trouble.
C. A scratch at point © can only be made by a broken needle or
by carelesshandling of the needle when replacingthe shuttle.
However, if the shuttle has a scratch at this point, the machine will
probably not be able to stitch.
D. A scratch at point © may damage the thread when releasing and
result in thread breakage. This kind of trouble does not occur fre
quently except with synthetic thread.
s
(S>
Fig. 23
Fig. 24
Fig. 25
rr
Fig. 26
From the library of: Superior Sewing Machine & Supply LLC

2) Thread entangled in the shuttle
A.If the shuttle race spring isnot properlypositioned, it will not handle
the thread properly, resultingin thread entanglement. Placethe spring
in the correct position as shownin Fig.9.
B. If the radius of the shuttle tip is too large, the thread will snag in the
shuttle.
Replace sucha shuttle. (Fig. 27)
C. The shuttle race must be positioned in relation to the needle, as
shown in Fig, 28, sothat there isa clearance ® of 7.5 mm (19/64")
between them. If the clearance (0) is smaller, the needle thread will
tend to snag.
D. If the needle thread tension istoo low, the thread will tend to snag.
3) Scratched shuttle driver
Make sure that the shuttle driver does not have any scratches at all on
its thread paths. Smoothness of the shuttle race surface is always im
portant, especially for high speed operation. The side edges © shown
in Fig. 29 must be smooth enough to allow the thread to passover them.
4) Clearance between the shuttle driver and the shuttle is too small.
A. The standard clearance between the shuttle driver and the shuttle is
0.3 to 0.5 mm (about 1/64"). If the clearance is smaller than that, it
will not allow the needle thread to smoothly pass and will cause
thread breakage or will leave an excessively long thread in the needle
eye. On the other hand, if the clearance is too large, the shuttle race
will make a noise. (Fig. 29)
B. Since there may be some cases where the above-mentioned clearance
is slightly different for hooking in and releasing the thread, provide
the correct clearance for release.
12^
0.3-0.5
©
-R
Fig. 27
Fig 28
Fig. 29
5) Needle plate needle hole guide
Every time a needle is broken, the needle plate needle hole guide is scratched. Remove such scratches from the
surface. Apply some abrasives to a strong thread and polish the scratched surface with it.
6) Needle touches the work clamp foot
A.This does not happen often. If the work clamp foot is not installed in the correct position, the needle may
touch its inner face and break the needle thread when stitching with a comparatively large feed pitch.
B. If the work clamp foot isscratchedby a needle,make its surfacesmooth with emery paper.
7) Scratched needle
A scratched needle will break the thread.
Ensure that the needle has a correct clearance at the shuttle blade point and is protected by the shuttle driver.
Use needle DP x 5 with LK-980 instead of needle LG x 5 which has been used with the conventional model
LK-232, because needle LG x 5 is easilyscratched and may cause thread breakage.
8) Needle thread tension istoo high when the needle sticks inthe material.
Adjust the thread take-up spring so that the stroke is reduced to 6 to 8 mm (15/64" to 5/16") and the initial
pressure is 30 to 50 g.
- 16 -
From the library of: Superior Sewing Machine & Supply LLC

(2) Thread breakage when trimming
Phenomenon Either the needle or the bobbin thread is accidentally broken while they are being trim
med.
Possible causes ®Thread release timingis not adequate.
©Movingknife is scratched.
©Height
of the counter knife is not correct.
•Shuttle race spring is scratched.
•The bottom surface of the needle plate needle hole guide is not smooth.
•Position of the moving knife is wrong.
Corrective measures
1) Thread release timingisnot adequate
A. If the timing of the thread release is too slow and the unreleased threads are trimmed off, either needle or
bobbin thread may be broken.
B. Adjust the thread release timing by means of the tension releaseleveraccording to the followingchart (See also
Fig. 30).
Needle thread
Tension release lever
1 Too long
Turn it up.
2
Not uniform
Turn it up.
3
Short and jumps.
Turn it down.
4Accidentally cut or jumps.
Turn it down.
2) Scratched moving knife
If the thread paths (A, B, C, D and E) on the moving knife are
scratched, they may break the needle. Remove such scratches
by applying abrasives. (Fig. 31)
3) Height of the counter knife
If the counter knife position is too high, the thread may touch
it and break before the moving knife arrives in the cutting
position. Correct the counter knife height by referring to the
standard adjustment.
4) Scratched shuttle race spring
If surface A is scratched, it will cut the thread. Remove such
scratches by applying some abrasives. (Fig. 32)
5) The bottom surface of the needle plate needle hole guide is not
smooth.
The threads drawn in by the moving knife for trimming will be
cut by the rough surface of the guide. (Fig. 33)
6) Position of the moving knife
If the needle thread is too tight when it passes through the
shuttle to form the last stitch, slightly increase the standard
distance of 1.5 mm (1/16") between the thread hookingpoint
of the moving knife and the nearest end of the needle hole in
the needle plate. (See Fig. 10)
- 17 -
Turn it up
Turn it down
Fig. 30
Fig. 31
5"
5
Fig. 32
,1
1 y i 1 ^
1\ 1
J \\
////jf/m
Moving knife
—r /
A
A Rough surface
Fig. 33
From the library of: Superior Sewing Machine & Supply LLC