JUKI DU-1181 Quick start guide

40040471
No.E371-00
ENGINEER’S MANUAL
1-NEEDLE, TOPAND BOTTOM FEED LOCKSTITCH MACHINE WITH A LARGE HOOK
DU-1181
DU-1181N
®

Introduction
This Engineer’s Manual is for technical service engineers. In the instruction manual for the maintenance engi-
neers of sewing machines and sewing workers in a sewing factory, how to operate a sewing machine is also
described in detail. However, in this manual, [Adjustment Procedure], [Results of Value Change for Adjustment],
and the roles of each component are described: these are not included in the instruction manual.
When maintenance is performed for our sewing machines, refer not only to this manual, but also to the instruction
manual and parts list.
This engineer’s manual describes the basic adjusting values as the reference values in the first page, and the
observed events caused by sewing and mechanical faults as the [Results of Value Change for Adjustment] and
[Adjustment Procedure] in the second page.

CONTENTS
1. Specifications ......................................................................................................... 1
2. Model Designation of the Head Section................................................................ 2
(1) DU-1181...................................................................................................................................... 2
(2) DU-1181N ................................................................................................................................... 2
3. Standard Adjustment.............................................................................................. 3
(1) Height of Needle Bar................................................................................................................. 3
(2) Timing between the Needle and the Hook .............................................................................. 3
(3) Lengthwise Position of Bobbin Case Positioning Finger ..................................................... 5
(4) Height and Position of the Feed Dog ...................................................................................... 5
(5) Feeding Alignment .................................................................................................................... 7
(6) Hand Lifter ................................................................................................................................. 7
(7) Upper Feed Motion.................................................................................................................... 9
1) Outer Presser Foot Position ................................................................................................................9
2) Amount of Interactive Movement of the Outer Presser Foot and the Inner Presser Foot .............9
3) Amount of Alternating Vertical Movement of the Outer Presser Foot and the Inner
Presser Foot..........................................................................................................................................9
(8) Upper Feed Differential........................................................................................................... 11
(9) Upper Feed Cam Timing......................................................................................................... 11
(10) Stitch Length in Forward and Reverse Feed ...................................................................... 13
(11) Thread Tensioner .................................................................................................................. 13
(12) Lubrication............................................................................................................................. 15
4. Grease Application................................................................................................ 17
5. List of Selective Combination Parts and Maintenance Parts............................ 19
6. Optional Parts........................................................................................................ 20
7. Troubles in Sewing and Corrective Measures.................................................... 21
8. Table Dimension Diagram .................................................................................... 24

1. Specifications
No. Item Specifications
1 Model DU-1181/DU-1181N
2Model Name 1-needle, top and bottom feed lockstitch machine with a large hook
3 Applications For medium-weight and heavy-weight materials
4 Sewing Speed Max. 2,000 rpm.
5Needle DP x 17#14 to #23 (Standard: #21), (DB x 1 available)
6Thread #40 to #8
7 Stitch Length Max. 9 mm (for both normal and reverse feed stitching)
8Presser Foot Lift Using hand lifter: 5.5 mm, Using a knee lifter: 15 mm
9 Stitch Length Regulating Method Using butterfly dial
10 Reverse Feed Stitching Using hand lever
11 Thread Take-up Lever Link type
12 Needle Bar Stroke 36.5mm
13 2mm to 5mm
14 Hook Large hook with automatic lubrication system
15 Feed mechanism Feed forked connecting slider type
16 Top Feed Mechanism Linked with hook driving mechanism
17 Using beveled gear
18 Lubrication Automatic lubrication (Manual lubrication only for top feed section)
19 Oil Return Flow Circulated with plunger pump
20 Lubricating Oil JUKI Machine Oil No. 7 (equivalent to ISO VG7)
21 Grease JUKI Grease A (White)
Tube of 10g grease (Part No. : 40006323), or
500g can (P/art No. : 23640204)
22 Bed Size 178mm to 476.6mm
23 Space under the Needle 261mm to 122.6mm
24 Motor 4P-400W Clutch Motor
25 Transmission Belt M Type V-Belt
26 Weight of Machine Head 31Kg
– 1 –
Amount of Alternating Ver-
tical Movement of the Walk-
ing Foot and Presser Foot
Rotating Hook Driving
Shaft System

12 3 456789
DU 1181–
2. Model Designation of the Head Section
(1) DU-1181
Name: 1-Needle, Top and Bottom Feed Lockstitch Machine with a Large Hook
– 2 –
8Specification Code for Destination
AStandard (WEEE compatible)
GChina (within China)
DU.S.A. and Japan
9Accessory Specification Code
AStandard
BCE compatibel
12 3 45678910
DU 1181N–
(2) DU-1181N
Name: 1-Needle, Top and Bottom Feed Lockstitch Machine with a Large Hook
9Specification Code for Destination
AStandard (WEEE compatible)
GChina (within China)
DU.S.A. and Japan
10 Accessory Specification Code
AStandard
BCE compatibel

A
B
(1) Height of Needle Bar
3. Standard Adjustment
Marker Lines engraved in the Needle Bar (for DP x 17): (Standard) A
Marker Lines engraved in the Needle Bar (for DB x 1): B
– 3 –
Requirement:
•The needle bar should be
brought to the lowest dead
point.
(2) Timing between the Needle and the Hook
1) Needle Lifting Amount and Positions of the 2) Clearance between the Needle and the
Needle and Blade Point of the Hook Blade Point of the Hook
Requirement:
•The needle bar should be lifted from
the lower dead point.
Standard Adjustment
Standard Adjustment
Coincidence with
the lower line en-
graved on the
needle bar
1.2mm
2.5mm
D
C
Marker Lines engraved in the Needle Bar (for DP x 17): (Standard) C
Marker Lines engraved in the Needle Bar (for DB x 1): D
0.02 to 0.07mm

1. Turn the hand-wheel to bring the needle bar to the lowest dead point.
2. Loosen the clamping screw of the needle bar connecting bracket
.
3. Align the marker line Aengraved in the needle bar to the lower end
of the needle bar lower metal and fasten the clamping screw of
the needle bar connecting bracket .
(Cautions) 1. For the needle DP x 17 (Standard), use the second
marker line AA
AA
Afrom the lowest, engraved in the
needle bar.
2. For the needle DB x 1, use the fourth marker line BB
BB
B
from the lowest, engraved in the needle bar.
3. After adjustment, make sure that the outer presser
foot does not come in contact with the needle bar.
oStitch skipping or thread breakage
may be caused.
– 4 –
oIrregular stitches, stitch skipping
or thread breakage may be
caused.
oIrregular stitches, particularly
isolated idling loops, will occur
when the hook timing is too early
or too late.
oIrregular stitches can be improved
when the hook timing is
appropriately set later.
oWhen the hook timing is set too
late, the thread tension may be
lowered.
oIsolated idling loops can be
improved when the hook timing is
set appropriately earlier.
1) Needle Lifting Amount and Positions of the Needle and Blade
Point of the Hook
1. Loosen the set screw of the throat plate and remove the throat plate.
2. Lift the needle bar 2.5 mm up from the lowest dead point.
3. Align the marker line C(for DP x 17) to the lower end of the needle
bar lower metal .
For the needle DP x 17 (Standard), use the lowest engraved
marker line Con the needle bar.
For the needle DB x 1, use the third marker line Dfrom the
lowest engraved on the needle bar.
4. When the positions of the needle and the blade point of the
hook are adjusted, loosen the hook set screw and turn the hook
by hand. Then align the center of the needle with the blade point
of the hook.
2) Clearance between the Needle and the Blade Point of the Hook
1. When setting the clearance between the needle and the blade
point , loosen the hook set screw so taht the clearance of 0.02
to 0.07 mm is provided between the needle and the blade point
.
Adjustment Procedure Results of Improper Adjustment
Adjustment Procedure Results of Improper Adjustment

1) Height of the Feed Dog
2) Position
Requirements:
•Feed Level: Maximum (9 mm)
•The clearances A and B between the throat
plate and the front and rear of the feed
dog should be equal.
Feed
base
Upper surface of
the throat plate
1.2mm
(4) Height and Position of the Feed Dog
– 5 –
Requirements
• Feed Level: Minimum (0mm)
•The maximum projection of the
feed dog should be 1.2 mm
above the surface of the throat
plate.
(3) Lengthwise Position of Bobbin Case Positioning Finger
Requirements:
•The needle entry should be within a range between
the center of the bobbin case positioning finger
projection and the shoulder section.
•The needle bar should be brought to the lowest dead
point.
Standard Adjustment
Standard Adjustment
AB
Range of Needle Entry

oThread tension failure may be
caused.
1) Height of the Feed Dog
1. Set the stitch dial to 0 mm on the scale.
2. Turn the hand-wheel and set the feed dog to the position where it
projects to the upper limit from the throat plate .
3. Loosen the feed driving fork end clamping screw to move the feed
driving fork end up and down and set the height of the feed dog
1.2 mm higher than the upper surface of the throat plate. Then, fix
the clamping screw.
2) Position
1. Set the stitch dial to 9mm on the scale.
2. Loosen the feed bar arm clamping screw and make sure that the
feed dog moves evenly to both the front and rear grooves on the
throat plate . Then, fix the clamping screw. (A = B)
– 6 –
1. Turn the hand-wheel to bring the needle bar to the lowest dead point.
2. Loosen the set screw of the bobbin case positioning finger .
3. Move the bobbin case positioning finger in the arrow direction so
that the needle entry is within the range between the center of the
projection on the bobbin case positioning finger and the shoulder
section and fix it using the set screw of the bobbin case position-
ing finger .
Adjustment Procedure Results of Improper Adjustment
Adjustment Procedure Results of Improper Adjustment
If the height of the feed dog is
excessive:
oThe feed dog will come in
contact with the throat plate .
oThe stitch length may become
larger than the value specified in
the stitch dial.
oIrregular stitches may be caused.
If the height of the feed dog is
insufficient:
oThe stitch length may become
shorter than the value specified in
the stitch dial.
oThe feed driving force may be
weakened.
Position:
oThe throat plate may come in
contact with the feed dog , and
the feed bar arm may come in
contact with the bed, resulting in
abnormal noise.

First or second
tooth
(5) Feeding Alignment
Requirements:
•Feed Level: Maximum (9 mm)
•Just when the first or second tooth at the front end of
the feed dog is lowered from the upper surface
of the throat plate, the center of the needle hole
should come in contact with the upper surface
of the throat plate.
•The marker dot Aengraved on the feed driving cam
should agree with the marker dot Bengraved on
the feed rock cam.
Standard Adjustment
A
B
Hand-wheel
side
Earlier Later
– 7 –
(6) Hand Lifter
Requirements:
•The lifting amount of the inner presser foot should
be 5.5 mm using the presser lifting lever.
Standard Adjustment
5.5mm

Feed Driving Cam
If the feed driving timing is earlier:
oIsolated idling loops will be
improved, but the thread tension
is lowered.
If the feed driving timing is later:
oIrregularstitchesmaybecaused.The
thread tension will be improved.
oThe needle breakage may be
caused.
The feed dog action will be different
in forward feed stitching from that in
the reverse feed stitching, compared
to that in standard adjustment.
Feed Rock Cam
oThe stitch length in forward and
reverse feed stitching, also, the
sewing pitch may differ from those
specified in the stitch dial. Irregular
stitching may be caused.
Feed Driving Cam
1. Set the stitch dial to 9 mm on the scale.
2. Loosen the feed driving cam set screw .
3. Turn the feed driving cam to the position where the center of the
needle hole contacts the upper surface of the throat plate and
the first or second tooth at the front of the feed dog sinks from the
upper surface of the throat plate. Then, fix the feed driving cam.
Feed Rock Cam
1. Set the stitch dial to 9 mm on the scale.
2. Loosen the feed rock cam set screw .
3. Align the marker dot Aengraved on the feed driving cam with the
marker dot Bengraved on the feed rock cam and fix the feed rock
cam.
(Reference) Three points; the screw No. 1 of the feed driving cam, the
screw No. 1 of the feed rock cam and the screw No. 2 of
the upper bevel gear are almost aligned in line.
(Caution) In the adjustment, if the feed rock cam is deviated in
the direction of the arm shaft, the machine operation
may feel heavy.
Adjustment Procedure Results of Improper Adjustment
– 8 –
If the height is too high:
oThe cloth feeding operation may
not be stable because the bottom
surface of the inner presser foot
is not in close contact with the
upper surface of the throat
plate.
1. Lift the hand lifter.
2. Loosen the clamping screw of the presser lifting bracket .
3. Adjust the distance from the upper surface of the throat plate to
the bottom surface of the inner presser foot to set it to 5.5 mm.
Then fix the hand lifter using the clamping screw of the presser
lifting bracket .
Adjustment Procedure Results of Improper Adjustment

1) Outer Presser Foot Position
2) Amount of Interactive Movement of the Outer Presser Foot and the Inner Presser Foot
3) Amount of Alternating Vertical Movement of the Outer Presser Foot and the Inner Presser Foot
Requirements:
•Feed Level: Maximum (9 mm)
•Aclearance of 2.4 mm should be provided
between the outer presser foot and inner
presser foot when the outer presser foot
and the inner presser foot are rested
on the throat plate and the outer presser
foot is brought closest to the inner
presser foot .
Requirements:
•Feed Level: Minimum (0 mm)
•The inner pressure foot should be 1.2
mm (the height of the feed dog) higher than
the outer presser foot .
•The amount of alternating vertical move-
ment of the outer presser foot should be
equal to that of the inner presser foot .
Requirement:
•The marker line engraved on the top feed
arm should be aligned with the center of
the cam rod hinge screw .
(Amount of alternating vertical movement
for top feed: 2.5 mm)
2.4mm
2.4mm
(7) Upper Feed Motion
– 9 –
Standard Adjustment
A
B
Amount of alternating
vertical movement
C
D

oIf the position is set incorrectly, top
feed components may come in
contact each other, which results
in abnormal noise.
oDepending on the materials to be
sewn, set the alternating vertical
movement of the outer presser
foot to a slightly larger value.
In the following cases:
• Sponge material is sewn.
•Overlapped section of the ma-
terial is sewn.
• Piping stitches are performed.
If the amount of alternating vertical
movement of the outer presser foot
and inner presser foot is greatly dif-
ferent from the standard values:
oThe stitch length may differ from
the value specified in the stitch
dial.
oThe feed force will be lowered. In
such a case, lower the sewing
speed (the number of motor revo-
lutions).
oDepending on the material to be
sewn, increase the height of the
presser feet.
In the following cases:
•Sponge material is sewn.
•Overlapped section of the ma-
terial is sewn.
oWhen the movement amount is in-
creased, the stitch length may dif-
fer from the value specified in the
stitch dial.
oWhen the movement amount is in-
creased, the feed force may be
decreased. In this case, lower the
sewing speed (the number of mo-
tor revolutions) slightly.
1) Position Adjustment for the Outer Presser Foot
1. Set the stitch dial to 9 mm on the scale.
2. Lower the inner presser foot onto the throat plate and turn the
hand-wheel. Stop the hand-wheel when the outer presser foot is
brought closest to the inner presser foot .
3. Loosen the connecting arm clamping screw .
4. Move the outer presser foot by hand and fix it with the connecting
arm clamping screw so that the clearance of 2.4 mm is provided
between the outer presser foot and the inner presser foot .
2) Amount of Interactive Movement of the Outer Presser Foot and
the Inner Presser Foot
1. Set the stitch dial to 9mm on the scale.
2. If the movement of the outer presser foot is insufficient:
(Movement of the inner presser foot is excessive).
(1) Loosen the clamping screw of the top feed arm .
(2) Align the thread take-up lever with the upper dead point and lower
the presser bar lifter.
(3) Move the top feed shaft slightly in the direction Band fix it
with the clamping screw .
3. If the movement of the outer presser foot is excessive:
(Movement of the inner presser foot is insufficient).
(1) Loosen the clamping screw of the top feed arm .
(2) Align the thread take-up lever with the upper dead point and lower
the presser bar lifter.
(3) Move the top feed shaft slightly in the direction Aand fix it
with the clamping screw .
(Caution)When the amount of alternating vertical amount is 3 mm
or more, the amount of alternating vertical movement of
the outer presser foot and the inner presser foot
should be set to equal.
3) Amount of Alternating Vertical Movement of the Outer Presser
Foot and the Inner Presser Foot
1. Loosen the cam rod hinge screw using a spanner of 14 mm.
2. Adjustthe cam rod boss positionbymovingitupordown( CD)
and fix it using the cam rod hinge screw .
o Upper Position C: Max. Movement (5 mm)
o Lower Position D: Min. Movement (2 mm)
(Cautions) 1. When the sewing operation is performed while the
amount of alternating vertical movement of the outer
presser foot and the inner presser foot is at around
the maximum, irregular stitch length may be caused.
In such a case, lower the sewing speed (reduce the
number of motor revolutions).
2. When the amount of alternating vertical movement
is changed for sewing a heavy material, make sure
that the needle bar does not come in contact with
the outer presser foot .
– 10 –
Adjustment Procedure Results of Improper Adjustment
AB
A<B

25.5±0.15mm
B
A
(8) Upper Feed Differential
– 11 –
Standard:
•Attach the slide block assembly
through the long eccentric hole so
that the distance between the cen-
ter of the upper feed driving shaft
and the center of the slide block
assembly bolt becomes 25.5 ±0.15
mm.
•The ratio of bottom feed to top feed
is 1:1.
(9) Upper Feed Cam Timing
Requirement:
•When the needle is lowered, and the
inner presser foot is also lowered and
aligned with the upper surface of the
throat plate, the needle eyelet top end
should be aligned with the upper surface
of the throat plate.
A
B
Upper position (Direction B)
Smaller top feed amount Lower position (Direction A)
Larger top feed amount
Standard Adjustment
Standard Adjustment
Top feed
Bottom feed
If the timing is early
(Direction A): If the timing is late
(Direction B):

If the timing is early (Direction A):
oThe stitch length may differ from
the value specified in the stitch
dial. (The stitch length becomes
smaller).
oThe load of the reverse feeding
may be given to the walking foot.
If the timing is late (Direction B):
oThe needle thread may easily split
finely.
oThe stitch length may differ from
the value specified in the stitch
dial. (The stitch length becomes
larger).
Cloth
Cloth
Deviation
If it is set to the upper position:
If it is set to lower position:
oCheck the item of (7) Upper Feed
motion-1) because the position of
the outer presser foot is changed.
oDeviation will occur between the
upper cloth and the lower cloth.
oChange it depending on the
sewing condition.
Cloth
Cloth
Deviation
1. Lift the presser bar lifter.
2. Loosen the slide block nut using a spanner of 11 mm.
3. Adjust the position of the slide block assembly up or down ( B,
A) and fix it using the slide block nut .
– 12 –
1. Loosen the two set screws of the upper feed cam .
2. When the upper surface of the throat plate is aligned with the
inner presser foot , turn the upper feed cam so that the top end
of the needle eyelet is aligned with the upper surface of the
throat plate. Then fix it, using the set screws .
The upper cloth is insuffi-
ciently fed, so will be curved
in the direction of arrow.
Adjustment Procedure Results of Improper Adjustment
Adjustment Procedure Results of Improper Adjustment
The upper cloth is exces-
sively fed, so will be curved
in the direction of arrow.

(10) Stitch Length in Forward and Reverse Feed
– 13 –
Requirements:
•Feed Level : 9 mm
•When the hand-wheel is turned by hand
and a cloth is sewn 10 stitches in both for-
ward and reverse feed stitching the differ-
ence in stitch length should be 2 mm or
less.
Standard Adjustment
Reverse feed
stitching Forward feed
stitching
Turn it in direction B.
Forward feed stitch length < Reverse
feed stitch length
A
B
Direction A
The stitch length for the forward
feed stitching is increased.
The stitch length for the reverse
feed stitching is decreased.
Direction B
The stitch length for the forward
feed stitching is decreased.
The stitch length for the reverse
feed stitching is increased.
Forward feed
stitching Reverse feed
stitching
(11) Thread Tensioner
Requirement:
•When the presser foot is lifted
and the distance between the
upper surface of the throat
plate and the bottom surface of
the inner presser foot is set
to 3.0 mm, the thread tension
disc comes in perfect contact
with the throat plate. When the
distance is set to 5.5 mm, the
thread tension disc perfectly
rises from the throat plate.
Standard Adjustment
3.0 mm: The thread tension disc lies
in perfect contact with the throat plate.
5.5 mm: The thread tension disc per-
fectly rises from the throat plate.
Turn it in direction A.
Forward feed stitch length > Reverse
feed stitch length

oThe stitch length in the normal
feed stitching may differ from that
in the reverse feed stitching.
1. Set the stitch dial to 9 mm on the scale.
2. Loosen the set screw of the pin on the feed regulator base .
3. Adjust the feed regulator base pin using a spanner of 14 mm, fix it
using the set screw .
(Caution) 1. After adjustment, make sure there is no backlash in
the forked link because it may cause stitch failure.
2. After adjustment, make sure that the stitch length in
forward feed is the same as that in reverse feed. Also,
reconfirm the amount (2 to 5 mm) of alternating verti-
cal movement for the upper feed, and the feeding align-
ment (positions of feed driving cam and feed rock
cam).
– 14 –
Adjustment Procedure Results of Improper Adjustment
If the thread tension disc starts rising
too early:
oThe thread tension disc may
rise during stitching, which may
cause thread tension failure.
If the thread tension disc starts
rising too late:
oThe thread tension disc may not
rise even when the hand lifter is
lifted. The thread is pulled out
while tension is given to it.
1. Insert a gauge of 3.0 mm into the gap between the throat plate upper
surface and the inner pressure foot and lower the hand lifter.
2. Loosen the set screw of the thread tensioner (assembly) .
3. Push in the thread tensioner (assembly) and fix it with the set
screw of the thread tensioner (assembly) at a position where
the thread tension disc does not rise.
Adjustment Procedure Results of Improper Adjustment

(12) Lubrication
– 15 –
DE
Standard Adjustment
Maximum Minimum
AA
CB
A
Splashed oil
Splashed oil
Oil Level (Trace)
1mm
2mm
Requirements: 2000rpm
<Adequate range of the hook oil level>
1) Face Section Oil Level Adjustment
2) Hook Oil Level Adjustment
Splashed oil
(little)
(Much)
Splashed oil
Oil Level (Trace)
1mm
Requirements: 2000rpm
<Adequate range of the face section oil level>
Fig. 1
(little)
(Much)

1) Face Section Oil Level Adjustment
1. Loosen the set screw of the oil preventive plate and remove the oil
preventive plate .
2. For adjustment of the oil level for the thread take-up lever and needle
bar crank section , turn the oil level adjusting pin .
3. Turn the oil level adjusting pin in the direction Bas seen from the
position shown in Fig.1 and, when the marker dot A, engraved on
the oil level adjusting pin, becomes close to the needle bar crank ,
the oil level becomes minimal. When the oil level adjusting pin is
turned in the direction Cfrom the position shown in Fig.1 and the
marker dot Abecomes close to the opposite side of the needle crank
, the oil level becomes maximal. Adjust pin properly the oil level
becomes optimali.
4. After adjusting the oil level, by using the oil level adjusting pin ,
warm-up the sewing machine for 30 seconds. Then insert an oil level
check (trace) paper from the arrow direction for 10 seconds to mea-
sure the oil level. (Speed: 2000 rpm.)
2) Hook Oil Level Adjustment
1. When the oil level adjusting screw , attached to the hook shaft
metal, is turned in the direction of + (Direction D), the oil level is
increased. When the oil level adjusting screw is turned in the direc-
tion of – (Direction E), the oil level is decreased. Adjust it properly.
2. After adjusting the oil level, using the oil level adjusting screw ,
warm-up the sewing machine for about 30 seconds. Then, insert the
oil level check paper into the hook bottom for 5 seconds to measure
the oil level. (Speed: 2000 rpm.)
– 16 –
Adjustment Procedure Results of Improper Adjustment
If the hook oil level is insufficient:
oThread tension may be
insufficient.
oThe hook will generate heat and
be worn out earlier, which may
cause seizure of the hook.
oIIrregular stitches may be caused.
If the hook oil level is excessive:
oThe thread will be stained with oil.
The cloth also may be stained with
oil.

– 17 –
4. Grease Application
The lubricating locations in component assembling work are as follows.
oIf any component disassembling work is performed, apply JUKI GreaseA(a tube of 10g white grease: P/N 40006323)
or 500g can (P/N 23640204) onto the specified locations.
∗Greasing :
o Machine Frame & Miscellaneous Cover Components
oFeed Mechanism Components
∗
∗
∗
∗
∗
oHand Lifter Components
oMain Shaft & Thread-up Lever Components ∗