JUKI LBH-781 User manual

BE078130B0A
MODEL LBH-781-782-783-784
Before operating your JUKI Lock
stitch Machine, please read this In
struction Book carefully in order to
operite it in the correct and efficient
HIGH SPEED SINGLE NEEDLE LOCKSTITCH STRIAGHX
BUTTON HOLING SEWING MACHINE
Instruction Book
CAUTION IN OPERATION
SPECIFICATIONS
1. The machine should rotate counterclockwise as observed
from the pulley. Take care not to rotate the machine in
the opposite direction.
2. Never start the machine before filling the machine base
with lubricating oil.
3. Remove the bobbin case and the needle thread from the
machine before performing the trial operation.
4. Clean up the sewing' hook and the bobbin thread
trimmer every day after sewing work. Also check the
level of the lubricating oil.
Application
Sewing speed
Buttonhole
length
Bar-tack width
Needle
Presser lift
Lubricating oil
1. MOTOR PULLEY AND V BELT
1. Motors of 300W, 4-pole are used for single-phase or three-phase
operation.
(If a 250W motor has to be used, operate the machine
at 3,100 s.p.m. or less.)
2.
M-type V belts are used.
3. Refer to the following table for the motor pulleys, V belt length,
and sewing speed.
Sewing speed Frequency Motor pulley Part No.
3,600 s.p.m.
B7262-781-000
B7263-781-000
3,400 s.p.m.
B725 6-781-000
B7257-781-000
B725 3-781-000
High speed
Vbelt
44 inch
43 inch
44 inch
42 inch
43 inch
Low speed
Vbelt
42 inch
42 inch
43 inch
42 inch
42 inch
LBH-781 LBH-782 LBH-783 LBH-784
Buttonholing for ordinary cloth, knit, etc.
Max. 3,600 s.p.m.
6.4~19.0mni 6.4~25.4mm 6.4~31.7mm 12.7~38.0m
(l/4"~3/4") (1/4"~1") ,i®/4"-l-l/4") (l/2"-I-l/2
mrATn''\ -S.Omin (3/32"~3/l 6")
DPx5 #11~#14
12mm {15/32")
JUKI New Defrix Oil No. 1
i
3,100 s.p.m.
B7254-781-000
42 inch
2,900 s.p.m.
B7258-781-000
B7259-781-000
42 inch
42 inch
42 inch
* How to install motor pulley
Place motor pulley 0 into the motor shaft so that
flat part © of the motor shaft aligns with first
setscrew o Then securely tighten setscrews 0 and
41 inch
(V belt Part No.: MTJ-VMOODDOO, V belt length)
*
How to install V belt
1. Mount high-speed V belt O oti accelerating pulley 0 and the largediameters of the motor pulley.
2. Mount low-speed V belt 0 on low-speed pulley 0 and the smalldiameters of the motor pulley.
3. By moving the motor from side to side, adjust the tension of Vbelts 0 and 0 so that they give an approx. 10 mm slack
when their middle portions are pushed lightly by hand.
4. Move the motor pulley back and forth to align V belts 0 and 0.
42 inch
i
Motor pulley
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2. SETTING UP THE THREAD
STAND
3. SETTING UP THE
MACHINE HEAD
Assemble the thread stand, and fix it in the table hole. Then tighten
lock nut O to fix the thread stand. If ceiling wiring can be made,
pass the power cable tl*iOugh spool rest rod 0.
Putting cushion 0 into hinge 0, insert hinge O into
the machine head. Then, place the machine head on
the machine base.
4. ATTACHING THE FLAT BELT
i
•iiiiiiiiliii'iiiiii
1. Removing screw 0, remove spring 0 from the suspension screw.
2. Pass belt 0 through belt shifter 0 so that the belt rotates in arrow o direction.
3. Reinstall screw 0 and spring
0.
4. Lift tripping lever 0 in the direction, pass the belt between latch B 0 and latch A 0.
5. Passing belt shifter 0 of the speed transmitter, attach the belt onto tension pulley 0 .
6. Put fixing pawl 0 in the second groove from the bottom of ratchet 0 to provide the belt with tension.
(NOTE) Some expansion or contraction In the belt caused by temperature or humidity may make It rather difficult to Install
the belt. However, the belt will restores its original length while In use.
5. INSTALLATION/REMOVAL OF BELT COVER
Aligning guide pin 0 with hole 0 in belt cover 0, push the
belt cover in the arrow direction until it snaps.
For removal of the belt cover, bring down the belt cover in the
direction opposite to the arrow, and slide it up.
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6. LUBRICATION
★ Before Starting the machine;
1. Fill the oil reservoir of the machine base with JUKI New
Defrix Oil No. I up to the level indicated by "HIGH",
2. Supplement the oil when the oil level has lowered below
the bottom line of oil gauge 0.
3. When the machine has been properly lubricated, the oil is
seen to run through the pipe from oil sight window O.
(Low speed operation permits easier observation of the
lubricating oil.)
Drain dirty oil by loosening oil drain screw 0 , and fill
the oil reservoir with fresh oil.
7. HOW^TO INSTALL
THE NEEDLE
* Adjusting the lubrication for the sewing hook
Adjust the volume of lubricating oil supplied to the sewing
hook by turning oil adjusting screws O for rough adjust
ment, and 0 for fine adjustment; oil volume is reduced
when turning the screws clockwise.
* Other lubricating points
1. Apply one or two drops of lubr'ijating oil to the arrowed
points once a week or every other week.
2. Apply two or three drops of lubricating oil only to O
point when the machine is newly set up or has been out of
use for a long time.
INSTALLATION/REMOVAL OF
BOBBIN CASE
1. Lift up and hold bobbin case
latch lever O between two fin
gers to remove it from the
hook. A bobbin does not fall
off the bobbin case while the
latch lever is lifted up.
2. For installation of the bobbin
case, push the bobbin case into
the hook so that it is supported
by the hook shaft, and then
snap in the latch lever.
★ Turn off the motor power. Use a DPx5 needle.
1. Loosening needle setscrew hold needle O
with its recessed part facing toward the operator,
2. insert the needle fully into the needle clamping
hole, and
3. securely tighten the needle setscrew.
9. WINDING THE BOBBIN
10. ATTACHING THE
BOBBIN
1. Hold and place a
bobbin into the bob
bin case so that the
bobbin is wound
counterclockwise.
2. Passing the thread
through thread outlet
O of the bobbin
case, pull the thread,
and the thread can be
drawn out from
thread outlet 0, pass
ing under the bobbin
winder tension spring.
^ Set the bobbin so that
it rotates in the arrow
direction when the
bobbin thread is
pulled.
Bobbin winder -
tension bracket
Adjusting
! screw
-^1 11
Bobbin winder /
trip latch /
X J I Adjusting nut
1. Fit a bobbin onto the bobbin
winder shaft.
2. Take the thread from the spool
and pass it through the guides
in the numerical order shown
in the figure, and wind the end
of the thread several turns
around the bobbin.
3. Push the bobbin winder trip
latch in the arrow direction,
and the bobbin will be wound.
4. Loosening the adjusting nut,
perform adjustment by screw
ing in or out the adjusting
screw so that the bobbin is
wound about four-fifths full.
5. If the bobbin is wound un
evenly, adjust the position of
the bobbin winder tension
bracket for proper and even
winding.
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12. REDUCTION OF
SEWING SPEED AND
EMERGENCY STOP
11. THREADING THE NEEDLE-THREAD
r©/. --
1. Pass the needle thread in the order as shown in the figures.
2. The threading can be done easily by using the needle threader
supplied with the machine.
•k Reduction of sewing speed
1. Turn hand stop crank O downwards to position
O, and
2. the machine will be immediately slowed down.
★ Emergency stop
1. Turn the hand stop crank downwards to position
o , and further upwards to position © and
2. the machine will stop immediately.
(NOTE) When the hand stop crank do not return,
push It down.
13. MANUAL FEED HANDLE
14. HOW TO HOLD THE
DESCENDIIMG KNIFE
m
When you wand to feed fabric manually after giving an emergency
stop or to resume sewing from the point at which thread was
broken, rotate manual feed handle O to operate the cloth feeding
mechanism.
(NOTE) Confirm that the needle does not stick in fabric before
turning the manual feed handle.
When you do , not want to cut fabric after sewing
because of thread breakage or some other reasons,
keep on pressing down knife stop lever Olightly
until the machine stops. Then the knife will not
descend.
15. TYPES OF STITCHES
(Whip stitch)
mmwmmimmimMimm
Pallarel side seam Bar tacking seam
(Purl stitch)
This machine is capable of forming two different types of
stitches, namely whip stitch and purl stitch.
(Whip stitch)
The whip stitch is formed in zigzag showing the needle
thread only on top of fabric, and the bobbin thread on the
bottom.
(Purl stitch)
When applying higher tension to the needle thread to permit
it to pass straight through fabric, the purl stitch is formed by
the bobbin thread which is pulled over from both sides to the
center line.
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16. THREAD TENSION
* Adjusting the thread tension for puri stitch:
1. Adjust the bobbin thread tension to approx. 15 to 20g by
adjusting screw 0
of the bobbin case.
2. Adjust tension controller No. 1 0 for proper needle thread
tension so that the bar-tack part is formed by well-shaped whip
stitches. If the tension is too low, bar tacking seam may form
thread knots on the rear face of fabric.
3. Adjust tension controller No. 2 0 for proper tension of the
pallarel side seams by judging from the stitch formation.
* Adjusting the thread tension for whip Stitch:
1. Adjust the bobbin thread tension to approx. 40 to 50g by
adjusting screw O of the bobbin case.
2. Exchange the adjusting springs of tension controllers No. 1 0
and No. 2 0 each other (the tension controller No. 2 will have a
weak spring).
3. Adjust tension controller No. 2 0 to prevent ravelling off at the
end of a seam.
4. The stitches of the parallel sides or bar-tack can be adjusted by
tension controller No. 1 0
17. ADJUSTING THE OVEREDGING
LENGTH(BUTTONHOLE
LEI^GJH)
1. Pull out cover 0, and raise cover 0 .
2. Loosen nut 0 by the spanner supplied with the machine. Set
point o to a desired length on scale 0 (this length is the same
with the knife width), and then retighten nut 0.
3. Through your trial sewing, adjust the overedging length accu
rately to the extent that the bar tacking seams are not cut by the
knife.
*Changing the work clamp check
Use work clamp check 0having the size nearly the same as that of a
buttonhole length.
By removing setscrew 0, a work clamp checks can be changed
together with a work clamp check holder as a set.
Work clamp check/Work clamp
check holder set Part No.
B1552-78I-OAO
B1552-782-0A0
BI552-7834)A0
Applicable knife width
l/4"~3/4"
l/4"~l-l/4"
-5-
*Adjusting the thread take-up spring (for
purl stitch)
The suitable range of the stroke of thread take-up
spring 0 is from 6 to 8mm with astarting tension
of 20 to 50g.
For adjusting the stroke of the thread take-up
spring, loose screw 0, and insert a thin screwdriver
into the slit of tension post 0 to turn the tension
post.
To adjust the tension of the thread take-up spring,
insert a thin screwdriver into the slit of tension post
0 to turn it, with screw 0 tightened. The tension
of the thread take-up spring increases when the
tension post is turned clockwise, and decreases
when turned counterclockwise.
18. REPLACING THE
KNIFE
When sharpening or replacing the knife, remove it as
follows:
1. Loosen setscrew 0, and remove knife 0 to
gether with the washer.
2. Attach the knife to the knife holder so that the
higher end of the slanted knife blade comes
down 2 to 3mm above the surface of the throat
plate when the knife if brought down to the
lowest position.
(NOTE): Do not forget to install the washer when
retightening the setscrew.
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19. ADJUSTING THE OVERDOING WIDTH (STITCH WIDTH AND BAR
TACKING WIDTH) AND OVEREDGING REFERENCE POSITION
The needle swings from right to left with the right base
line established as the reference position.
Perform the adjustment as follows:
1. To adjust stitch width ©, screw in or out screw 0,
and set pointer 0 to a desired value on scale plate
0. The actually sewn stitch width will be the half of
the set scale value (mm).
2. For adjustment of bar tacking width ©, screw in or
out screw
0, and set pointer 0 to the value
indicated by scale plate pointer 0, making the bar
tacking width twice as large as the stitch width.
3. Adjust the position of right base line © by screwing
in or out screw 0 so that it is kept away from the
cutting line of the knife. As screw 0 is screwed in,
the right base line moves to the left.
4. Through your trial sewing, further perform fine
adjustment.
5. It is not necessary to adjust the position of left base
line ® since it remains unchanged when the stitch
width is changed. However, the left base line should
be moved to the left by screwing in screw 0 if it is
cut by the knife.
20. CHANGING THE NUMBER OF STITCHES
No. of No. of
stitches of stitches of
small gears large gears
* Spur gears
1. By selecting the spur gears, you can control the number of
stitches as shown in the table.
2. Alphabetical marks like A, B, C, etc., and numerals like
123, 152, etc. are both engraved on each spur gear for
identification.
3. Use a combination of gears which have the same alpha
betical marks.
4. The numeral engraved on the gear installed in the rear
position will represent the number of stitched provided by
the then combination of spur gears.
The circled alphabetical symbols in the above table show that the gears
are included in the standard accessories. All other gears are optional
attachments,
* Attaching the spur gears to their shafts
1. Push gear 0 into the shaft so that it is securely fixed by
the pin on gear bushing 0 located nearer to an operator.
2.
For installing gear 0 on the pin of rear gear bushing 0,
push gear 0 into the shaft while turning it in the arrow
direction.
3. When setting the number of stitches to 93 or less, loosen
setscrew 0, and move low-speed cam 0 in the arrow
direction to prevent the knife from dropping during high
speed operation.
21. ADJUSTING THE PRESSER BAR PRESSURE
iiinp
i
The presser bar goes up 12mm when the pedal is fully
stepped down,
To adjust the pressure applied by the presser bar to fabric,
turn presser spring regulator 0. When the pressure is not
enough to prevent fabric from puckering, turn regulator 0
clockwise.
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22. NEEDLE-TO-HOOK RELATION
1
* Set the needle to hook relation In the following way:
1. Bring down the needle bar to the lowest point when the needle is coming down through the center of the needle hole on the
throat plate.
2. Loosen needle bar connection screw 0> adjust the height of the needle bar.
(Setting the needle bar)
3. Insert the part "1" of timing gauge Q into the gap between the bottom end of needle bar 0 and throat plate 0.
4. Retighten the needle bar connection screw to adjust the position of the sewing hook.
(Setting the hook)
5. Loosen setscrew 0 of the hook sleeve by the bar spanner supplied with the machine.
6. Rotate the driving pulley in the correct direction until the needle starts to go up from its lowest point.
7. Insert
the part "2" of the timing gauge into the gap between the bottom end of the needle bar and the throat plate, where the
bottom end of the needle bar touches the top of the part "2" of the timing gauge.
8. Aligh blade point 0 of the sewing hook with the center of needle©, and make adjustment so that a clearance of approx.
0.5mm (1/64") is provided between the needle and the blade point of the hook. Then, securely retighten the setscrew of the
hook sleeve.
(NOTE): Ifstitchesare skipped, lowerthe needlebar by approx. 0.5mm (1/64") from the timinggauge "1".
23. ADJUSTION THE
BOBBIN THREAD
WINDER
H
Loosen screw 0 to make adjustment so that the
clearance between bobbin thread winder pulley ©
and belt © becomes approx. 1mm (33/64") when
pulley O is apart from the belt.
If, however, the belt touches the pulley, adjust the
tnesion by tension pully 0 to decrease the deflec
tion of the bell. And if the belt still touches the
pulley, increase the clearance to more than 1mm
(3/64'^).
24. ADJUSTING THE
SPEED TRANSMITTER
ii
I
* Adjustment of the position of the belt shifter
When the hand stop crank is turned down to the low speed position,
loosen screw 0 and allow the belt to move onto low-speed pulley
0, moving the position of belt shifter ©.
* Adjusting the stopper screw
Perform adjustment by stopper screw 0 so that belt shifter 0 does
not cause the belt to come off high-speed pulley ©during high
speed operation.
-7 -
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25. ADJUSTMENT OF THE NEEDLE THREAD TRIMMER
p
HRJ
* Attaching the trimmer
Loosen setscrew O. and adjust the height of trimmer Set
the height of trimmer Q as low as possible, provided that it
does not touch work clamp check in order to minimize the
length of remaining thread on the needle after trimming.
*Closing timing of the needle thread trimmer
Adjust the closing timing of the needle thread trimmer so that
the trimmer completely closes when it advances farthest.
To perform the adjustment, loosen screw 0> and move needle
thread trimmer driving plate A 0 back and forth. When the
needle thread trimmer driving plate is moved towards you, the
closing timing is delayed with reduced amount of closing.
(NOTE) Confirm that an allowance of 0.3 to 0.5 mm Is left
between the blades of the trimmer when the trimmer
has completely closed.
if there is no such allowance, the trimmer would
Interfere with the operation of the needle thread
trimmer driving plate, preventing smooth movement
of lifting lever 0 .
* Opening timing of the needle thread trimmer
Adjust the timing of the thread trimmer so that the trimmer
begins to open gradually at a distance of approx. 2.5 to 3mm
(3/32" to 1/8") from the start.
To perform the adjustment, loosen screw O. ai^d move needle
thread trimmer driving plate B 0 back and forth. As it moves
towards you, the trimmer begins to open earlier.
(NOTE): Take care not to cause the already fixed needle
thread trimmer driving plate A to get out of position.
26. ADJUSTMENT OF NEEDLE THREAD TRIMMER HOLDER
AND LIMITING PLATE
sMIM
0.5 mm
Loosen setscrew O, and install and adjust limiting plate 0 so
that it comes in contact with the blocking arm 0 at the time
of slow start of the machine (when latch B O is engaged with
latch A 0).
Needle thread trimmer holder 0should be installed in such
manner that it engages with cam 0 by 0.5mm (1/64") when
the needle thread trimmer opens.
27. TIMING FOR DROPPING THE KNIFE
§.
Loosen screws o, and move knife tripping segment 0 in the
direction shown by the arrow, and the knife will drop earlier.
Adjust it so that the knife drops two to three stitches before
the machine stops.
A3
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28. TROUBLE, CAUSE, AND REMEDY
Trouble
Cause
Remedy
1. Needle thread is
broken.
(1) The tension of the tension controller
No. 2 is too tight.
(2) The tension or the stroke of the take-up
spring is too great.
(3) Blade point of sewing hook has burr or
scratches.
(4) Poor timing of the sewing hook.
(5) The thread path has scratches.
(6) The needle is too thin.
0 Decrease the tension of the tension
controller No. 2
o
Decrease the tension or the stroke of the
take-up spring.
o Buff the blade point of the sewing hook,
or replate the sewing hook,
o Readjust the sewing hook's timing by the
timing gauge,
o Buff the thread path by cloth files, etc.
o Replace by a thick needle.
2. Thread slips out
of the needle.
(1) The needle thread trimmer opens too
early.
(2) The needle thread trimmer opens when
the work clamp check is comming down.
(3) The whip stitch is not formed at the
start of sewing.
(4) Wrong threading.
0 Move back the needle thread trimmer
driving plate B.
o Move back the needle thread trimmer
driving plate B.
o Decrease the tension of the tension
controller No. 1.
O Perform correct threading.
3. Wobbling stitches
are formed in the
overedging seams.
(1) The tension disc No. 2 is too loose.
(2) The tension and stroke of the take-up
spring is not enough.
(3) Bobbin thread tension is too high.
o Increase the tension of the tension disc No.2.
o Readjust the take-up spring.
o Decrease the bobbin thread tension (15 to
20g for purl stitches).
4. Wobbling stitches
are formed at the
start of sewing,
5. The needle thread
at the first bar
tacking comes out
and lumps on the
bottom of cloth.
(1) The tension disc No. 1 is too loose.
1 (2) The position of the needle thread trimmer
is too high.
1(3)
The stroke of the take-up spring is too
great.
(1) The tension disc No. 1 is too loose.
(2) The bobbin thread tension is too high.
o Increase the tension of the tension disc
No. 1 (15 to 30g).
o Lower the trimmer as low as possible,
provided it does not come in contact with
the work clamp check,
o Decrease the stroke of the take-up spring,
and increase the spring pressure.
o Increase the tension of the tension disc
No. 1.
o Decrease the bobbin thread tension (15 to
20g).
6. Stitches float over
cloth.
(1) Bobbin thread tension is not enough.
(2) Bobbin thread slips out of the thread
path on the bobbin case.
o Increase the bobbin thread tension,
o Properly thread the bobbin case.
7. Stitches are
skipped.
(1) The work clamp check is too large for
the buttonhole.
(2) The cloth is made of light-weight
materials.
o Change the work clamp check with a
smaller one.
o Delay the timing of the needle and the
sewing hook. (Lower the needle bar by
approx. 0.5mm (1/2"))
I
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29. STITCH'NG TROUBLLS CAUSED BY OTHER REASONS
Trouble
Cause
Remedy
Page
1. Starting pedal
does not work.
(The work clamp
arm is not lifted
up fully.)
(1) Needle plate, needle plate base or bobbin
thread trimmer is clogged with fibrous
dust.
(2) The needle thread trimmer is interfered by
the work clamp check or the trimmer
driving plate.
0 Tilt the machine head and clean them up.
o Readjust the installation of the trimmer,
or the position of the trimmer driving
plate.
8
2. Machine does not
reach the high
speed even when
the pedal is stepped
down fully.
(1) The hand stop crank is not in the
correct position.
(2) The belt shifter of the speed transmitter
has not changed to the high speed pulley.
o Correct the position of the hand stop
crank.
o Lubricate the shifter driving pin.
1
3. A loud noise is
produced with a
stop-motion, or
sewing speed does
not lower at the
end of sewing.
(1) Improper setting of the low speed cam
for small numbers of stitches.
(2) The flat belt is too loose.
(3) The low speed V belt is too loose.
o Readjust the setting of the low speed cam.
o Increase the belt tension by the tension
pulley.
o Increase the tension of the V belt by
the motor.
6
2
1
4. Stop-motion is not
smooth.
(1) Stop-motion lever needs lubrication.
(2) The belt shifter of the speed transmitter
has not changed to the low speed pulley.
o Lubricate the stop-motion lever,
o Readjust the position of the belt shifter.
3
7
5. The machine does
not lubricate.
(1) Oil level in the oil reservoir is too low.
(2) Oil is not circulated.
OFill the lubricating oil up to "HIGH"
mark.
o Apply oil to the oil return felts.
3
3
6. Knife is dropped
during high speed
rotation.
(1) Position of the knife tripping segment
is not correct.
(2) The setting of the low speed cam for
numbers of stitches is not correct.
o Adjust the position of the driving cam so
that the knife is dropped down at a delayed
timing.
o Correct the setting of the low speed cam.
8
6
7. Knife is dropped
1 even if the needle
thread is broken.
(1) The machine is threaded incorrectly. o
Correct the threading.
•
8. Needle is broken.
(1) The needle is bent.
(2) The needle and the hook blade touch
with each other.
(3) Needle thread trimmer hits the needle
when opening its blades.
o Replace the needle,
o Readjust the positions of the needle and
the sewing hook,
o Readjust the position of the trimmer,
o Adjust so that the limiting plate and the
blocking arm touch each other at the time
of starting.
3
7
8
8
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(Please do not hesitate to contact our distributors or agents \
in your area for further informations when nec^sary. /
fOKYO JUKI INDUSTRIAL CO..LTD.
Head Office &Plant: 2-1, 8-chome, Kokuryo-cho, Chofu-shi, Tokyo, Japan
Business Office: 23-3, Kabukt-cho 1-chome, Shinjuku-ku, Tokyo 160, Japan
Cable: JUKI TOKYO Telex: 22967; 232-2301
Phone: [phone] Printed in Japan(T)
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