Brother T-8421D User manual

Instruction Manual
TWIN NEEDLE DIRECT DRIVE LOCK STITCHER
T-8421D
T-8422D
T-8452D
T-8722D
T-8752D
Please read this manual before using the machine.
Please keep this manual within easy reach for quick reference.

Safety Instructions
Thank you very much for buying a BROTHER sewing machine. Before using your new machine, please read the
safety instructions and the explanations given in the instruction manual.
With industrial sewing machines, it is normal to carry out work while positioned directly in front of moving parts such
as the needle and thread take-up, and consequently there is always a danger of injury that can be caused by these
parts. Follow the instructions from training personnel and instructors regarding safe and correct operation before
operating the machine so that you will know how to use it correctly.
Safety indications and their meanings
This instruction manual and the indications and symbols that are used on the machine itself are provided in order to
ensure safe operation of this machine and to prevent accidents and injury to yourself or other people.
The meanings of these indications and symbols are given below.
Indications
DANGER
The instructions which follow this term indicate situations where failure to follow the instructions will result in
death or serious injury.
WARNING
The instructions which follow this term indicate situations where failure to follow the instructions could result in
death or serious injury.
CAUTION
The instructions which follow this term indicate situations where failure to follow the instructions may result in
minor or moderate injury.
Symbols
This symbol ( ) indicates something that you should be careful of.
The picture inside the triangle indicates the nature of the caution that must be taken. (For example, the
symbol at left means “beware of injury”.)
This symbol ( ) indicates something that you must not do.
This symbol ( ) indicates something that you must do.
The picture inside the circle indicates the nature of the thing that must be done. (For example, the
symbol at left means “you must make the ground connection”.)
i

Notes on safety
Notes during use
DANGER
• Wait at least 5 minutes after turning off the power switch and disconnecting the power cord from the
wall outlet before opening the control box cover. Touching areas where high voltages are present
can result in severe injury.
WARNING
• Do not allow the machine to come into contact with liquids. Otherwise it may cause fire, electric
shocks, or operating problems.
• If any liquid gets inside the sewing machine (machine head or control box), immediately turn off the
power and disconnect the power plug from the electrical outlet, and then contact the place of
purchase or a qualified technician.
Notes on the operating environment
CAUTION
• Do not connect anything to the USB port other than the USB media. Otherwise, problems with
operation may result.
• Use the sewing machine in an area which is free from sources of strong electrical noise such as
electrical line noise or static electric noise. Sources of strong electrical noise may cause problems
with correct operation
• Any fluctuations in the power supply voltage should be within ±10% of the rated voltage for the
machine.Voltage fluctuations which are greater than this may cause problems with correct operation.
• The power supply capacity should be greater than the requirements for the sewing machine's power
consumption. Insufficient power supply capacity may cause problems with correct operation.
• The ambient temperature should be within the range of 5°C to 35°C during use.Temperatures which
are lower or higher than this may cause problems with correct operation.
• The relative humidity should be within the range of 45% to 85% during use, and no dew formation
should occur in any devices.Excessively dry or humid environments and dew formation may cause
problems with correct operation.
• In the event of an electrical storm, turn off the power and disconnect the power cord from the wall
outlet. Lightning may cause problems with correct operation.
Notes during installation
CAUTION
• Do not connect the power cord plug until installation is complete. The machine may operate if the
treadle is depressed by mistake, which could result in injury.
• Secure the table so that it will not move when tilting back the machine head. If the table moves, it
may crush your feet or cause other injuries.
• Use both hands to hold the machine head when tilting it back or returning it to its original position. If
only one hand is used, the weight of the machine head may cause your hand to slip, and your hand
may get caught.
• Machine installation should only be carried out by a qualified technician.
• When securing the cords, do not bend the cords excessively or fasten them too hard with staples.
Otherwise, fire or electric shocks may occur.
• Be sure to wear protective goggles and gloves when handling the lubricating oil and grease so that
they do not get into your eyes or onto your skin. Otherwise inflammation can result. Furthermore, do
ii

not drink the oil or eat the grease under any circumstances. Diarrhea or vomiting may result. Keep
the oil and grease out of the reach of children.
• Contact your Brother dealer or a qualified electrician for any electrical work that may need to be
done.
• The sewing machine weighs approximately 50 kg (110 lb).The installation should be carried out by
two or more people.
• Turn off the power switch before inserting or removing the plug. Otherwise damage to the control
box may result.
• If using a work table which has casters, the casters should be secured in such a way so that they
cannot move.
• Be sure to connect the ground. If the ground connection is not secure, you run a high risk of
receiving a serious electric shock, and problems with correct operation may also occur.
Notes during sewing
CAUTION
• Turn off the power switch while threading and replacing the bobbin, and when not using or going
away from the sewing machine. The machine may operate if the treadle is depressed by mistake,
which could result in injury.
• Attach all safety devices before using the sewing machine. If the machine is used without these
devices attached, injury may result.
• Do not touch any of the moving parts or press any objects against the sewing machine while sewing.
Otherwise, it may result in injury or damage to the sewing machine.
• Secure the table so that it will not move when tilting back the machine head. If the table moves, it
may crush your feet or cause other injuries.
• Use both hands to hold the machine head when tilting it back or returning it to its original position. If
only one hand is used, the weight of the machine head may cause your hand to slip, and your hand
may get caught.
• Do not hold the machine head by the panel when tilting it back or returning it to its original position.
Otherwise, it may result in injury or damage to the sewing machine.
• To prevent problems, do not use objects with sharp points to operate the operation panel.
• This sewing machine should only be used by operators who have received the necessary training in
safe use beforehand.
• The sewing machine should not be used for any applications other than sewing.
• Be sure to wear protective goggles when using the machine. If goggles are not worn, there is the
danger that if a needle breaks, parts of the broken needle may enter your eyes and injury may result.
• If using a work table which has casters, the casters should be secured in such a way so that they
cannot move.
• If an error occurs in machine operation, or if abnormal noises or smells are noticed, immediately turn
off the power switch. Then contact your nearest Brother dealer or a qualified technician.
• If the machine develops a problem, contact your nearest Brother dealer or a qualified technician.
iii

Notes during cleaning
CAUTION
• Turn off the power switch and disconnect the power cord before carrying out these operations. The
machine may operate if the treadle is depressed by mistake, which could result in injury.
• Secure the table so that it will not move when tilting back the machine head. If the table moves, it
may crush your feet or cause other injuries.
• Use both hands to hold the machine head when tilting it back or returning it to its original position. If
only one hand is used, the weight of the machine head may cause your hand to slip, and your hand
may get caught.
• Do not hold the machine head by the panel when tilting it back or returning it to its original position.
Otherwise, it may result in injury or damage to the sewing machine.
• Be sure to wear protective goggles and gloves when handling the lubricating oil and grease so that
they do not get into your eyes or onto your skin. Otherwise inflammation can result. Furthermore, do
not drink the oil or eat the grease under any circumstances. Diarrhea or vomiting may result. Keep
the oil and grease out of the reach of children.
Notes during maintenance and inspection
CAUTION
• Turn off the power switch and disconnect the power cord plug before carrying out inspection,
adjustment or repairs, or when replacing consumable parts such as the rotary hook or knives. The
machine may operate if the treadle is depressed by mistake, which could result in injury.
• If the power switch needs to be left on when carrying out some adjustment, be extremely careful to
observe all safety precautions.
• Secure the table so that it will not move when tilting back the machine head. If the table moves, it
may crush your feet or cause other injuries.
• Use both hands to hold the machine head when tilting it back or returning it to its original position. If
only one hand is used, the weight of the machine head may cause your hand to slip, and your hand
may get caught.
• Do not hold the machine head by the panel when tilting it back or returning it to its original position.
Otherwise, it may result in injury or damage to the sewing machine.
• Maintenance and inspection of the sewing machine should only be carried out by a qualified
technician.
• Always be sure to turn off the power switch and then wait one minute before opening the motor
cover. If you touch the surface of the motor, it may cause burns.
• Ask your Brother dealer or a qualified electrician to carry out any maintenance and inspection of the
electrical system.
• When replacing parts and installing optional parts, be sure to use only genuine Brother parts.
Brother will not be held responsible for any accidents or problems resulting from the use of non-
genuine parts.
• If any safety devices have been removed, be absolutely sure to re-install them to their original
positions and check that they operate correctly before using the machine.
Note regarding modification
CAUTION
• To prevent accidents and problems, do not modify the sewing machine (including control devices) by
yourself. Brother will not be held responsible for any accidents or problems resulting from
modifications made to the sewing machine.
iv

Warning labels
The following warning labels appear on the sewing machine. Please follow the instructions on the labels at all times
when using the machine. If the labels have been removed or are difficult to read, please contact your nearest
Brother dealer.
v

(1)
(2)
1 Moving parts may cause injury.
2 Operate with safety devices installed. 1
3 Turn off the power before carrying out
operations such as threading, changing the
needle, bobbin, knives or hook, cleaning and
adjusting.
(3)
Be sure to connect the ground. If the ground
connection is not secure, you run a high risk of
receiving a serious electric shock, and problems
with correct operation may also occur.
(4)
Direction of operation
(5)
Be careful to avoid injury from the moving thread
take-up.
(6)
Be careful not to get your hands caught when
returning the machine head to its original position
after it has been tilted.
(7)
1* Safety devices:
(A)Finger guard
(B)Thread take-up cover
(C)Motor cover
vi

Names of major parts
<T-8452D,8752D>
(1) Bobbin winder
(2) Thread wiper(T-8422D/T-8452D/T-8722D/
T-8752D)
(3) Lifting lever
(4) Quick reverse (Hand switch)
(5) Presser foot
(6) Control box
(7) Knee lifter assembly
(8) Power switch
(9) Stitch length dial
(10) Reverse lever
(11) Oil gauge window
(12) Machine pulley
(13) Operation panel
(14) Cotton stand
(15) Stop lever(T-8452D/T-8752D)
(16) Thread take-up cover
(17) Finger guard
(18) Motor cover
vii

Machine specifications
A- 4 7
Rotary hook Standard hook Large hook
B- 2 5
Stitch function Fixed needle bar Split needle bar
C- 1 2
Thread trimmer －○
D
- 4 T
Quick reverse ○ ○
Thread wiper ○ －
E- 0 3
Lubrication type Minimum lubrication Semi dry
F
- F 3 5 7
Use Foundation
Light-weight and
medium-weight
materials
Heavy-weight
materials
Heavy-weight
materials (For
extra thick thread)
T-8421D
- -T3F -T0F -T03
Max. sewing speed 3,000 sti/min 4,000 sti/min 4,000 sti/min
Start backtacking and
continuous backtacking speed 250 to 1,800 sti/min
End backtacking speed 1,000 sti/min
Max. stitch length 4mm
Presser foot
height
Lifting lever 7mm
Knee lifter 13mm
Feed dog height 1mm
Needle (DP×5) #9 to #14 #11 to #16
Motor AC servo motor (4-pole, 550W)
Power supply Single-phase 200V-230V, 3-phase 200V-230V, Power consumption 500 VA
Control circuit Microprocessor
viii

T-8422D
- -403 -405
Max. sewing speed 4,000 sti/min 3,000 sti/min
Start backtacking and continuous
backtacking speed 250 to 1,800 sti/min
End backtacking speed 1,000 sti/min
Max. stitch length 4mm 5mm
Presser foot height Lifting lever 7mm
Knee lifter 10mm
Feed dog height 1mm
Needle (DP×5) #11 to #16 #14 to #22
Motor AC servo motor (4-pole, 550W)
Power supply Single-phase 200V-230V, 3-phase 200V-230V, Power consumption
500 VA
Control circuit Microprocessor
T-8452D
- -403 -405
Max. sewing speed 3,000 sti/min
Start backtacking and continuous
backtacking speed 250 to 1,800 sti/min
End backtacking speed 1,000 sti/min
Max. stitch length 5mm
Presser foot height Lifting lever 7mm
Knee lifter 10mm
Feed dog height 1mm
Needle (DP×5) #11 to #16 #14 to #22
Motor AC servo motor (4-pole, 550W)
Power supply Single-phase 200V-230V, 3-phase 200V-230V, Power consumption
500 VA
Control circuit Microprocessor
T-8722D, T-8752D
- -403(T-8752D only) -405, -407
Max. sewing speed 3,000 sti/min
Start backtacking and continuous
backtacking speed 250 to 1,800 sti/min
End backtacking speed 1,000 sti/min
Max. stitch length 7mm
Presser foot height Lifting lever 7mm
Knee lifter 10mm
Feed dog height 1mm
Needle (DP×5) #11 to #16 #14 to #22
ix

Motor AC servo motor (4-pole, 550W)
Power supply Single-phase 200V-230V, 3-phase 200V-230V, Power consumption
500 VA
Control circuit Microprocessor
x

1Installation ..................................................................................................................................... 1
Points to note before installation ........................................................................................................... 1
Table processing diagram............................................................................................................ 2
Installing the sewing machine...................................................................................................... 3
Lubrication ................................................................................................................................... 7
Connecting the cords................................................................................................................. 10
Turning on the sewing machine power ...................................................................................... 15
Carrying out test sewing ............................................................................................................ 15
Adjusting the treadle operation .................................................................................................. 16
2Preparation before sewing ......................................................................................................... 17
Installing the needle............................................................................................................................. 17
Removing the bobbins......................................................................................................................... 18
Winding the lower thread..................................................................................................................... 18
Installing the bobbin cases .................................................................................................................. 19
Threading the upper thread................................................................................................................. 22
Adjusting the stitch length.................................................................................................................... 24
Using the knee lifter plate .................................................................................................................... 24
Using the thread wiper......................................................................................................................... 24
Screens where sewing is possible............................................................................................. 25
Corner sewing ..................................................................................................................................... 25
Stopping the needle bars (left and right).................................................................................... 25
Number of stitches: quick-reference guide ................................................................................ 26
3Using the operation panel (Basic operations).......................................................................... 27
Name and function of each operation panel item................................................................................ 27
About the home screens...................................................................................................................... 27
About the detailed home screen ................................................................................................ 28
About the quick home screen .................................................................................................... 29
Types of icons............................................................................................................................ 30
Menu screen........................................................................................................................................ 30
Program setting method ...................................................................................................................... 31
Program structure ...................................................................................................................... 31
Setting start backtacking............................................................................................................ 34
Main sewing settings ................................................................................................................. 34
Setting end backtacking............................................................................................................. 35
Using program individual functions and program common functions ........................................ 36
Using the production counter..................................................................................................... 40
Using the lower thread counter.................................................................................................. 40
Setting the home screen mode.................................................................................................. 41
Adjusting the needle up stop position ........................................................................................ 42
4Using the operation panel (Advanced operations) .................................................................. 43
Adding and deleting steps ................................................................................................................... 43
Editing steps ........................................................................................................................................ 44
Setting main sewing parameters when several steps exist ....................................................... 44
Setting the sewing start step ............................................................................................................... 45
Table of Contents
xi

Copying programs ............................................................................................................................... 45
Initializing the currently-selected program ........................................................................................... 46
Setting the working pace ..................................................................................................................... 46
Setting memory switches (standard) ................................................................................................... 47
List of memory switches ...................................................................................................................... 48
Hand switch ......................................................................................................................................... 53
Setting hand switch functions .................................................................................................... 55
Reading and writing data using USB media........................................................................................ 56
Data read/write items in USB media mode and media folder structure ..................................... 56
Initialization.......................................................................................................................................... 58
5Sewing.......................................................................................................................................... 59
Points to note before sewing ............................................................................................................... 59
Sewing ....................................................................................................................................... 59
Backtacking ............................................................................................................................... 60
Sewing condensed stitches ....................................................................................................... 60
6Adjusting the stitch tension ....................................................................................................... 62
Adjusting the thread tension................................................................................................................ 62
Adjusting the upper roller pressure...................................................................................................... 63
Adjusting the presser foot floating amount (minute lifting amount)...................................................... 64
Adjusting the upper thread trailing length after thread trimming.......................................................... 65
Adjusting the thread take-up amount................................................................................................... 66
7Daily cleaning procedures.......................................................................................................... 68
Points to note when cleaning............................................................................................................... 68
Cleaning..................................................................................................................................... 68
Lubrication ................................................................................................................................. 68
Checking the condition of the needle and upper thread ............................................................ 69
Draining lubricating oil ............................................................................................................... 69
Lubricating the oil cover (every 6 months)................................................................................. 69
Adding grease (when the grease up warning screen is displayed) ........................................... 70
8Adjusting the sewing machine (Standard adjustments) ......................................................... 72
Points to note when making adjustments............................................................................................ 72
Adjusting the safety switch position ........................................................................................... 73
Adjusting the thread take-up amounts of the thread tension springs......................................... 74
Adjusting the tension of the thread tension spring..................................................................... 75
Adjusting the clearance between the rotary hook and the needle plate .................................... 75
Adjusting the clearance between the rotary hook and the opener............................................. 76
Adjusting the height of the presser foot ..................................................................................... 77
Adjusting the needle and rotary hook timing.............................................................................. 78
Installing the feed dog................................................................................................................ 81
Adjusting the position of the feed dog........................................................................................ 82
Adjusting the height of the feed dog .......................................................................................... 83
Adjusting the feed dog angle ..................................................................................................... 84
Adjusting the rotary hook lubrication amount............................................................................. 85
9Troubleshooting .......................................................................................................................... 87
Troubleshooting during sewing............................................................................................................ 87
List of error codes................................................................................................................................ 94
xii

Points to note before installation
CAUTION
• Do not connect the power cord plug until installation is complete. The machine may operate if the
treadle is depressed by mistake, which could result in injury.
• Secure the table so that it will not move when tilting back the machine head. If the table moves, it
may crush your feet or cause other injuries.
• Use both hands to hold the machine head when tilting it back or returning it to its original position. If
only one hand is used, the weight of the machine head may cause your hand to slip, and your hand
may get caught.
• Machine installation should only be carried out by a qualified technician.
• Contact your Brother dealer or a qualified electrician for any electrical work that may need to be
done.
• The sewing machine weighs approximately 50 kg (110 lb).The installation should be carried out by
two or more people.
About the machine set-up location
• Do not set up this sewing machine near other equipment such as
televisions, radios or cordless telephones. Such equipment may
be affected by electronic interference from the sewing machine.
• The sewing machine should be plugged directly into an AC wall
outlet. Operation problems may result if extension cords are
used.
Carrying the machine
• The sewing machine should be carried by the arm and the motor
cover by two people as shown in the illustration.
• Hold the motor cover (A) by hand also so that the pulley does not
rotate.
• Do not hold the operation panel.
1Installation
1Installation
1

Tilting back the machine head
• Hold section (B) with your foot so that the table does not move,
and then push the arm with both hands to tilt back the machine
head.
• Do not hold the operation panel.
Returning the machine head to its original position
1. Clear away any tools, etc. which may be near the table holes.
2. While holding the face plate with your left hand, gently return the
machine head to the upright position with your right hand.
• Do not hold the operation panel.
Table processing diagram
• The top of the table should be 40 mm in thickness and should be strong enough to hold the weight and with-
stand the vibration of the sewing machine.
• Drill holes as indicated in the illustration below.
(1) Control box mounting hole
(2) Head rest hole
(3) Cord hole
(4) Cotton stand hole
2

Installing the sewing machine
1Install the control box and the
connecting rod.
(1) Control box
(2) Bolt [4 pcs.]
(3) Nut [8 pcs.]
(4) Spring washer [4 pcs.]
(5) Washer [4 pcs.]
(6) Connecting rod
(7) Nut
2Install the oil pan.
(1) Head cushion(left) [2 pcs]
(2) Head cushion(right) [2 pcs]
(3) Oil pan
(4) Oiler
1Installation
3

3Install the rubber cushions and the
knee lifter complying bar.
(1) Rubber cushion [2 pcs.]
(2) Knee lifter complying bar
4Install the machine head.
(1) Hinge [2 pcs.]
(2) Machine head
(3) Head rest
CAUTION
Tap the head rest securely into the table
as far as it will go. If the head rest is not
tapped in as far as it will go, there is the
danger that the machine head will not be
sufficiently stable when it is tilted back.
5Install the operation panel.
(1) Operation panel
(2) Screw [2 pcs.]
(Use for tightening rear cover)
4

6Install the cotton stand.
(1) Cotton stand
(2) Rubber cushion [2 pcs.]
(3) Washer
(4) Nut
Securely tighten the nut so that the
two rubber cushions and the washer
are securely clamped and so that the
cotton stand does not move.
Adjusting the knee lifter
7Turn the machine pulley so that the
feed dog is below the top of the
needle plate.
8Lower the presser foot (2) by using
the lifting lever (1).
9Loosen the nut (3).
10 Turn the screw (5) to adjust so that
the amount of movement (play) in
the knee lifter (4) is approximately 2
mm when the knee lifter plate is
gently pressed.
After adjustment is completed,
securely tighten the nut (3).
11 Loosen the nut (6).
12 Turn the screw (7) until the distance between the end of the screw (7) and the knee lifter (4) is approximately
5mm.
1Installation
5

13 Turn the adjusting screw (7) to
adjust so that the presser foot (2) is
at the desired position within a
distance of 13 mm from the needle
plate when the knee lifter plate is
fully pressed.
14 After adjustment is completed,
securely tighten the nut (6).
6

Lubrication
The sewing machine should always be lubricated and the oil supply replenished before it is used for the first time,
and also after long periods of non-use.
Use only the lubricating oil <JXTG Nippon Oil & Energy Corporation Sewing Lube 10N; VG10> specified by
Brother.If this type of lubricating oil is difficult to obtain, the recommended oil to use is <Exxon Mobil Essotex SM10;
VG10>.
CAUTION
• When cutting the nozzle of the oil tank, hold the base of the nozzle securely. If you hold the end of
the nozzle, injury from the scissors may result.
• Do not connect the power cord plug until adding lubricating oil is complete. The machine may
operate if the treadle is depressed by mistake, which could result in injury.
• Be sure to wear protective goggles and gloves when handling the lubricating oil and grease so that
they do not get into your eyes or onto your skin. Otherwise inflammation can result. Furthermore, do
not drink the oil or eat the grease under any circumstances. Diarrhea or vomiting may result. Keep
the oil and grease out of the reach of children.
1Hold the base of the nozzle of the accessory oil
tank (1), and use scissors to cut about half-way
along the straight section (A) of the nozzle.
2Loosen and remove the nozzle, and then remove
the seal (2).
3Tighten the nozzle.
Lubricating the oil cover
4Tilt back the machine head.
5Remove the rubber cap (1).
6Use the accessory oil tank (2) to pour lubricating oil
into the oil cover (3) until the oil level reaches the
reference line (4).
CAUTION
Do not fill with lubricating oil past the reference line (4). If
you pour in too much lubricating oil, it may spill out when
the machine head is tilted back.
7Replace the rubber cap (1).
8Return the machine head to its original position.
1Installation
7