Brother T-8421C Instruction Manual Download Page 45

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T-8421C, 8422C, 8452C, 8722C, 8752C

6. USING THE G50 OPERATION PANEL (ADVANCED OPERATIONS)

6-3. LOCK key

When the power switch is turned on, the LOCK key (1) turns
ON. (The icon (2) is illuminated.)
In this state, the following three key operations are disabled
so that the setting values cannot be changed accidentally.

FUNC key (3)

This key is used to make settings for various functions.

ENTER key (4)

This key is used to accept function settings.

MAX key (5)

This key is used to change the maximum sewing speed.

* Refer to the Service Manual for details on using these

keys.

4194M

Summary of Contents for T-8421C

Page 1: ... 8421C 8422C T 8452C 8722C T 8752C Please read this manual before using the machine Please keep this manual within easy reach for quick reference TWIN NEEDLE DIRECT DRIVE LOCK STITCHER INSTRUCTION MANUAL ...

Page 2: ... 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 ...

Page 3: ...ry CAUTION The instructions which follow this term indicate situations where failure to follow the instructions could cause injury when using the machine or physical damage to equipment and surroundings 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 bew...

Page 4: ...tallation 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 Do not connect the power cord until installation is complete The machine may operate if the treadle is depressed by mis...

Page 5: ...l 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 Be sure to wear protective goggles and gloves when handling the lubricati...

Page 6: ...are present can result in severe injury Turn off the power before opening the cover 4 Be careful not to get your hands caught when returning the machine head to its original position after it has been tilted 3 5 Be careful to avoid injury from the moving thread take up 6 Be sure to connect the ground If the ground connection is not secure you run a high risk of receiving a serious electric shock a...

Page 7: ...T 8421C 8422C 8452C 8722C 8752C v Control box Oil pan 2166B Transformer box 100V 400V system only Oil tank 2506B ...

Page 8: ...ed stitches 31 5 5 Sewing pleat presser stitches 32 5 6 Using the lower thread counter 33 6 USING THE G50 OPERATION PANEL ADVANCED OPERATIONS 34 6 1 Names and functions 34 6 2 Adjusting the needle up stop position 35 6 3 LOCK key 36 6 4 Resetting all settings to their defaults 37 7 USING THE G10 OPERATION PANEL BASIC OPERATIONS 38 7 1 Names and functions 38 7 2 Sewing start and end backtack stitch...

Page 9: ...E ROTARY HOOK LUBRICATION AMOUNT 63 13 STANDARD ADJUSTMENT 64 13 1 Safety switch position 64 13 2 Thread take up amount for thread take up spring 65 13 3 Thread take up spring tension 66 13 4 Clearance between rotary hook and needle plate 67 13 5 Clearance between rotary hook and opener 68 13 6 Presser foot height 68 13 7 Needle and rotary hook timing 69 13 8 Installing the feed dog 71 13 9 Feed d...

Page 10: ...e hook 2 5 B Stitch function Fixed needle bar Split needle bar 1 2 C Thread trimmer 4 T Quick reverse D Thread wiper 0 3 E Lubrication type Minimum lubrication Semi dry F 3 5 7 F Use Foundation Light weight and medium weight materials Heavy weight materials Heavy weight materials For extra thick thread A B C D E F 2167B ...

Page 11: ...ing lever 7 mm Presser foot height Knee lifter 10 mm Feed dog height 1 mm Needle DP 5 11 16 14 22 Motor AC servo motor 4 pole 550W Control circuit Microprocessor T 8452C 403 405 407 Max sewing speed 3 000 sti min Start backtacking and continuous backtacking speed 250 1 800 sti min End backtacking speed 1 000 sti min Max stitch length 5 mm Lifting lever 7 mm Presser foot height Knee lifter 10 mm Fe...

Page 12: ...rse Actuator 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 8452C 8752C Safety devices 16 Thread take up cover 17 Finger guard 2168B G10 operation panel basic function LED G50 operation panel advanced function LCD ...

Page 13: ...ad may cause your hand to slip and your hand may get caught About the machine set up location Do not set up this sewing machine near other equipment such as televisions radios or cordless telephones otherwise 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 extensi...

Page 14: ...gh to hold the weight and with stand the vibration of the sewing machine Drill holes as indicated in the illustration below 3 2 Installation 1 Control box 1 Control box 2 Bolts 3 pcs 3 Nuts 3 pcs 4 Spring washers 3 pcs 5 Washers 3 pcs 2 Connecting rod 6 Connecting rod 7 Nut 4127M 2170B Cotton stand hole Cord hole Head rest hole Control box mounting hole ...

Page 15: ...752C 3 INSTALLATION 6 3 Oil pan 1 Head cushions left 2 pcs 2 Head cushions right 2 pcs 3 Oil pan 4 Oiler 4 Rubber cushions 1 Rubber cushions 2 pcs 2 Nails 4 pcs 5 Knee lifter complying bar 3 Knee lifter complying bar 2874M 2875M ...

Page 16: ...not pushed in as far as it will go the machine head will not be sufficiently stable when it is tilted back 7 Operation panel 1 Operation panel 2 Screws 2 pcs Use for tightening rear cover 8 Cotton stand 1 Cotton stand NOTE Securely tighten the nut 4 so that the two rubber cushions 2 and the washer 3 are securely clamped and so that the cotton stand 1 does not move 2171B 2172B 2878M ...

Page 17: ...urn the screw 8 to adjust so that the amount of play in the knee lifter 7 is approximately 2 mm when the knee lifter plate 1 is gently pressed 5 Securely tighten the nut 6 6 Loosen the nut 9 7 Turn the screw 10 until the distance between the end of the screw 10 and the knee lifter 7 is approximately 5 mm 8 Turn the adjusting screw 10 to adjust so that the presser foot 5 is at the desired position ...

Page 18: ...bricating oil is difficult to obtain the recommended oil to use is Exxon Mobil Essotex SM10 VG10 1 Hold 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 2 Loosen and remove the nozzle and then remove the seal 2 3 Tighten the nozzle Lubricating via the oil cover 1 Tilt back the machine head 2 Remove the rubber cap 1...

Page 19: ...10 Lubrication Apply 1 2 drops of oil to the places indicated by the arrows 2200B Rotary hook race left and right 2174B 2887M Semi dry type and minimum lubrication type Minimum lubrication type only Do not apply oil for semi dry types T 8452C 8752C ...

Page 20: ... be done Do not connect the power cord until all cords have been connected The machine may operate if the treadle is depressed by mistake which could result in injury When securing the cords do not bend the cords excessively or fasten them too hard with staples otherwise there is the danger that fire or electric shocks could occur Be sure to connect the ground If the ground connection is not secur...

Page 21: ... such a way that the connector does not get pulled out All cords that come out from the control box should be secured to the cord holder 2 using the repeat cable tie 1 otherwise vibration from the sewing machine may cause the cords to become disconnected which can cause problems with the operation of the control box 4139M Push in securely until the tabs 6 engage Closing the cover 4141M Removal Sec...

Page 22: ...1 Attach an appropriate plug to the power cord 4 The green and yellow wire is the ground wire 2 Insert the power plug into a properly grounded electrical outlet NOTE Take care when tapping in the staples 3 to make sure that they do not pierce the cords Do not use extension cords otherwise machine operation problems may result Oil pan 4143M Green and yellow wire ground wire Seen from underneath tab...

Page 23: ...priate plug to the power cord 4 The green and yellow wire is the ground wire 2 Insert the power plug into a properly grounded electrical outlet NOTE Take care when tapping in the staples 5 to make sure that they do not pierce the cords Do not use extension cords otherwise machine operation problems may result 4145M Green and yellow wire ground wire Operator 2178B 2177B ...

Page 24: ...ord clamps 2 pcs 9 Power cord 1 Attach an appropriate plug to the power cord 9 The green and yellow wire is the ground wire 2 Insert the power plug into a properly grounded electrical outlet NOTE Take care when tapping in the staples 7 to make sure that they do not pierce the cords Do not use extension cords otherwise machine operation problems may result Operator 4145M 2179B Green and yellow wire...

Page 25: ...3 1 Safety switch position 2 Then check that it sews at high speed when the treadle 3 is gently pressed to position C 3 After pressing the treadle 3 forward check that the needle is lowered to the top of the needle plate when the treadle 3 is returned to the neutral position A when needle down stopping has been set 4 If the treadle 3 is pressed to position D thread trimming is carried out for mode...

Page 26: ...comes gradually stronger at b c and d respectively Backward depression sensitivity adjustment 1 Loosen the nut 3 and turn the bolt 4 When the bolt 4 is tightened the treadle operation becomes heavier and when it is loosened the operation becomes lighter 2 Tighten the nut 3 Adjusting the treadle stroke Remove the nut 5 and then move the connecting rod joint 6 from the position in figure A to the po...

Page 27: ...achine may operate if the treadle is depressed by mistake which could result in injury 1 Turn the machine pulley to move the needle bar to its highest position 2 Loosen the screws 1 3 Insert the needle 2 straight in as far as it will go so that the long groove is facing inward and then securely tighten the screws 1 2461B Long groove 2462B T 8421C 8422C 8722C T 8452C 8752C Long groove ...

Page 28: ...le is depressed by mistake which could result in injury Latch type 1 Open the slide plates 1 by moving them to the right and left 2 Pull the rotary hook latches 2 upward and them remove the bobbins 3 Bobbin case type 1 Open the slide plates 1 by moving them to the right and left 2 Lift up the latch 2 of the rotary hook and then remove the bobbin case 3 3 Remove the bobbin 2463B 2464B ...

Page 29: ... that the thread is not loose anywhere along the thread path 4 Push the bobbin presser arm 3 toward the bobbin 1 5 Raise the presser foot with the lifting lever 6 Depress the treadle Lower thread winding will then start 7 Once winding of the lower thread is completed the bobbin presser arm 3 will return automatically 8 After the thread has been wound on remove the bobbin and cut the thread with th...

Page 30: ...2 Return the rotary hook latch 3 to its original position 3 Turn the machine pulley to rotate the rotary hook 2 until the tension spring 4 is visible 4 Pass the thread through slit 5 in the rotary hook and then pass it under the thread tension spring 5 Pull out the thread to a length of approximately 50 mm 6 Close the slide plates There is an anti spin spring 6 inside the rotary hook The anti spin...

Page 31: ...hread through the thread hole 8 and pull out about 50 mm B C 1 Pass the thread through slot 3 and under the thread tension spring 4 2 Pass the thread through slots 5 and 6 and then through the spring 7 3 Pass the thread through the thread hole 8 and pull out about 50 mm 3 Insert the bobbin case 2 into the rotary hook 4 Push latch 9 of the rotary hook flat 5 Close the slide plates There is an anti ...

Page 32: ...reading the upper thread The machine may operate if the treadle is depressed by mistake which could result in injury Turn the machine pulley and raise the thread take up 1 before threading the upper thread This will make threading easier and it will prevent the thread from coming out at the sewing start Thread the left side thread first ...

Page 33: ...cifications and T 8452C 405 Pass the thread through For foundation specifications and T 8452C 405 Center Refer to p 54 If the tension discs are opened as follows the thread will become easier to thread Models with thread trimmer Press the tension release plate 2 Models without thread trimmer Press the tension release plate 2 or operate the lifting lever or the knee lifter to raise the presser foot...

Page 34: ...e looking at the finished stitches When turning the stitch length dial 2 from a larger setting to a smaller setting it will be easier to turn the dial if the reverse lever 3 is pushed to the halfwaydown position 3 Turn the dial lock lever 1 firmly to the left to lock the stitch length dial 2 Check that the stitch length dial 2 does not rotate 4 7 Using the knee lifter The presser foot 2 can be rai...

Page 35: ...ht needle bar Move the stop lever 1 to the R position To resume twin needle sewing Press the push lever 2 The stop lever 1 will then return to its original position automatically 4 9 2 Number of stitches quick reference guide For 1 4 needle width Determine the stitch length from the chart above to make beautiful corner stitching The number of stitches of the outer needle varies according to the co...

Page 36: ...0 up to 99 When the key is pressed the setting decreases from 99 down to 0 3 Start backtack key When this key is pressed so that the indicator illuminates the number of start backtack stitches 0 99 in the A and B stitch number displays is sewn 4 End backtack key When this key is pressed so that the indicator illuminates the number of end backtack stitches 0 99 in the C and D stitch number displays...

Page 37: ... depressed to the maximum amount The sewing speed can also be adjusted while sewing is in progress When the key is pressed the sewing speed becomes faster When the key is pressed the sewing speed becomes slower 13 Thread trimming lock key models with thread trimmer only When this key is pressed so that the indicator illuminates the sewing machine stops in the needle up position without thread trim...

Page 38: ...til the set number of start backtack stitches has been sewn 4 End backtacking is carried out After it has finished the thread is trimmed automatically models with thread trimmer and the sewing machine stops in the needle up position NOTE If the treadle is depressed backward before sewing of the set number of start backtack stitches is complete end backtacking will not be carried out If the indicat...

Page 39: ...g is being carried out the sewing machine will stop at the point where the treadle returns to the neutral position If the treadle is depressed again operation will resume from the point where it was interrupted If the indicator of the thread trimming lock key is illuminated the sewing machine will stop in the needle up position without thread trimming being carried out Automatic sewing When the AU...

Page 40: ... the thread trimming key to turn on the thread trimming function When the treadle is continuously depressed thread trimming is carried out after the fixed stitches have been sewn Automatic sewing When the AUTO key is pressed to turn on the automatic sewing function the fixed stitches are sewn simply by depressing the treadle once without needing to depress it continuously Start and end backtack se...

Page 41: ...ead trimming is carried out models with thread trimmer Automatic sewing and automatic thread trimming These functions cannot be used Start and end backtack sewing The start backtack key and end backtack key can be pressed to turn on the backtack sewing function If changing the number of end backtack stitches indicated in C and D press the pleat presser sewing key to turn off the pleat presser sewi...

Page 42: ...y 1 for every 10 stitches sewn When the value goes below zero 0 a minus sign appears and counting continues to a maximum of 999 2 When the value goes below 0 a warning icon 1 illuminates and an electronic buzzer sounds for 5 seconds 3 Sewing will be possible even after the treadle is returned to the neutral position and the sewing machine stops However after the treadle has been depressed backward...

Page 43: ...the sewing machine is stopped sewing will be carried out at slow speed 250 sti min while the actuator switch is being pressed NOTE If you press the actuator switch while sewing is in progress backtack stitches will be sewn Correction sewing cannot be carried out while the indicator of the pleat presser sewing key 8 is illuminated If you press this key again while the icon 22 is illuminated the ico...

Page 44: ...u press the key the setting value will increase and the needle up stop position will become lower If you press the key the setting value will decrease and the needle up stop position will become higher The setting range is from 5 to 10 A setting value of 10 corresponds to an angle of rotation of approximately 10 for the upper shaft 4 The setting values will be memorized 4192M 5 Normal sewing machi...

Page 45: ...minated In this state the following three key operations are disabled so that the setting values cannot be changed accidentally FUNC key 3 This key is used to make settings for various functions ENTER key 4 This key is used to accept function settings MAX key 5 This key is used to change the maximum sewing speed Refer to the Service Manual for details on using these keys 4194M ...

Page 46: ... the RESET key press the power ON switch init ALL will appear in orange in the main display 1 1 2 Press for 2 seconds or more Once initialization is complete the main display will return to green 4192M 3 Initialization mode will be exited and normal sewing machine operation will then be possible 4193M If the X keys 2 are pressed at this time you can select the items to be initialized as shown belo...

Page 47: ...s from 9 down to 0 3 Start backtack key When this key is pressed so that the indicator illuminates the number of start backtack stitches 0 9 in the A and B columns of the display are sewn 4 End backtack key When this key is pressed so that the indicator illuminates the number of end backtack stitches 0 9 in the C and D columns of the display are sewn When the treadle is depressed backward the end ...

Page 48: ...nue operating until the set number of start backtack stitches has been sewn 4 End backtacking is carried out After it has finished the thread is trimmed automatically models with thread trimmer and the sewing machine stops in the needle up position NOTE If the treadle is depressed backward before sewing of the set number of start backtack stitches is complete end backtacking will not be carried ou...

Page 49: ...dels with thread trimmer and then the needle bar will stop in the needle up position NOTE If the treadle is returned to the neutral position while continuous backtacking is being carried out the sewing machine will stop at the point where the treadle returns to the neutral position If the treadle is depressed again operation will resume from the point where it was interrupted If thread trimming lo...

Page 50: ...tails on turning the lock function off refer to 8 7 Lock function 1 Activating setting mode While pressing the end backtack key press the power ON switch 2 Setting the needle up stop and needle down stop positions When the key is pressed the UP display will appear When the key is pressed the dn display will appear Needle up stop Needle down stop NOTE If the start backtack key 1 is pressed once mor...

Page 51: ...ile pressing the end backtack key press the power ON switch 2 Selecting SloW slow start Press twice 3 Enabling and disabling slow start When the key is pressed the on display will appear When the key is pressed the oFF display will appear Slow start enabled Slow start disabled NOTE If the start backtack key 1 is pressed once more the start backtack indicator will switch off and the display will re...

Page 52: ...ck key press the power ON switch 2 Selecting Corr correction sewing Press once 3 Enabling and disabling correction sewing When the key is pressed the on display will appear When the key is pressed the oFF display will appear Correction sewing enabled Correction sewing disabled NOTE If the start backtack key 1 is pressed once more the start backtack indicator will switch off and the display will re...

Page 53: ...abling thread trimming lock When the key is pressed the on display will appear When the key is pressed the oFF display will appear Thread trimming locked Thread trimming not locked NOTE If the start backtack key 1 is pressed once more the start backtack indicator will switch off and the display will return to the setting item 4 The setting will be stored and the display will return to the setting ...

Page 54: ...he lock function off refer to 8 7 Lock function 1 2 Setting the maximum sewing speed The maximum sewing speed is set in columns A and B Setting can be carried out in units of 100 sti min When the key is pressed the setting increases When the key is pressed the setting decreases 3 The display will return to what was shown before the MAX key was pressed NOTE While the indicator of the MAX key is ill...

Page 55: ...ecome lower If you press the key the setting value will decrease and the needle up stop position will become higher The setting range is from 5 to 10 A setting value of 10 corresponds to an angle of rotation of approximately 10 for the upper shaft 4 The setting will be stored and the display will return to the setting item 5 Normal sewing machine operation will then be possible 4206M For details o...

Page 56: ...to OFF The lock will be canceled and the functions can then be set 8 8 Resetting all settings to their defaults If the sewing machine stops operating normally the cause may be that an incorrect setting may have been made for the memory data by means of memory switches for instance In such cases it may be possible to restore normal operation by following the steps given below to initialize the memo...

Page 57: ... 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 9 1 Sewing 1 While holding the two upper threads with your fingers turn th...

Page 58: ...ever 2 is pressed during sewing the feed direction will be reversed When it is released the feed direction will return to normal Actuator switch rotation function The actuator switch can be rotated 90 degrees as shown in the illustration Select the position A or B that is easier to use 2916M 2917M 2918M ...

Page 59: ...topper 6 until it touches the reverse stitching lever plate 7 4 Tighten the screw 5 to secure the stopper 6 Sewing 1 Return the stitch length dial 4 to the stitch length for normal sewing 2 Turn the dial lock lever 3 firmly to the left to lock the stitch length dial 4 3 Start sewing 4 At the position where you would like to start sewing condensed stitches press the actuator switch 1 or the reverse...

Page 60: ...wer thread tension CAUTION Turn off the power switch before adjusting the lower thread tension The machine may operate if the treadle is depressed by mistake which could result in injury Turn the adjusting screw 1 to adjust Upper thread tension After the lower thread tension has been adjusted adjust the upper thread tension so that a good even stitch is obtained 1 Lower the presser foot 2 Adjust b...

Page 61: ... but strong enough so that the material does not slip Refer to Adjusting screw height in the table below as a guide to adjustment 1 Loosen the adjusting nut 1 2 Turn the presser adjusting screw 2 to adjust the presser foot pressure 3 Tighten the adjusting nut 1 Reference values Use Adjusting screw height For foundation Approx 34mm For light weight and medium weight materials Approx 34mm For heavy ...

Page 62: ... material to check the floating amount Guide to adjustment when sewing curves When the material is placed under the presser foot 1 and the feed dog 2 is moved to its lowest position and the material is moved there should ideally be some resistance in the material If the floating amount is too small Ease of working handling will be poorer when sewing curves If the floating amount is too large The s...

Page 63: ...h as synthetic yarns When sewing light materials When sewing with a stitch length of 2 mm or less When sewing under any of the above three conditions and you would like to prevent skipped stitches thread tightening problems such as looping or thread breakages Guide to adjustment The standard thread take up amount is when the thread tension spring 3 starts to move when the loop is moved to point B ...

Page 64: ...e weight of the machine head may cause your hand to slip and your hand may get caught 11 1 Daily cleaning procedures The following cleaning operations should be carried out each day in order to maintain the performance of this machine and to ensure a long service life Furthermore if the sewing machine has not been used for a long period of time carry out the following cleaning procedures before us...

Page 65: ...s Minimum lubrication specifications Pour lubricating oil into the oil cover 1 about once every six months Semi dry specifications Pour lubricating oil into the oil cover 1 about as often as grease is applied Use only the lubricating oil NIPPON OIL 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 ...

Page 66: ...ssible when the treadle is depressed NOTE If you do not apply grease when the GrEASEUP notification flashes the notification will continue to flash each time the power is turned on until you reset the notification by carrying out the procedure on the following page If you continue to use the sewing machine after the GrEASEUP notification appears without applying grease or without carrying out the ...

Page 67: ...rease to all locations shown on the next page in the same way 7 Carry out the reset procedure given on the next page NOTE Once the grease tube has been opened remove the nozzle from the tube attach the cap securely and store the tube in a cool dark place The grease should be used as quickly as possible When using the grease again remove any old grease from inside the nozzle first Store the tube aw...

Page 68: ...sumed For example 100 means that 100 of the grease has been consumed 3 Press the RESET key 4 4 The display 3 will change to GuCt 0 5 Press the FUNC key 5 The display 3 will change to stitch number display mode and treadle operation will be possible This completes the reset procedure Pour oil into the oil cover at the same time Refer to p 9 2201B 2202B Turn the machine pulley until the screw 1 can ...

Page 69: ...l be possible when the treadle is depressed NOTE If you do not apply grease when the GrUP notification flashes the notification will continue to flash each time the power is turned on until you reset the notification by carrying out the procedure on the following page If you continue to use the sewing machine after the GrUP notification appears without applying grease or without carrying out the r...

Page 70: ...rease to all locations shown on the next page in the same way 7 Carry out the reset procedure given on the next page NOTE Once the grease tube has been opened remove the nozzle from the tube attach the cap securely and store the tube in a cool dark place The grease should be used as quickly as possible When using the grease again remove any old grease from inside the nozzle first Store the tube aw...

Page 71: ... xxx represents the amount of grease consumed For example 100 means that 100 of the grease has been consumed 5 Press the continuous backtack key 5 for 2 seconds or more 6 The display 1 will change to 0 7 Press the thread wiper key 6 The display 3 will change to stitch number display mode and treadle operation will be possible This completes the reset procedure Pour oil into the oil cover at the sa...

Page 72: ...out sewing any material following the same start stop pattern as when actually sewing 7 Place the lubrication amount check sheet 2 to the left of the rotary hook the right side is the right side of the rotary hook and hold it in place while running the sewing machine at the normal sewing speed for approximately 8 seconds Any type of paper can be used as the lubrication amount check sheet 2 8 Check...

Page 73: ... could result in injury When carrying out inspection adjustment and maintenance When replacing consumable parts such as the rotary hook and knife If the power switch needs to be left on when carrying out some adjustment be extremely careful to observe all safety precautions 13 1 Safety switch position The standard installation position for the safety switch 1 is shown in the illustration at left A...

Page 74: ...e screw 6 Height of stopper left 4 for left thread 1 Loosen the screw 7 and then slide the stopper left 4 to adjust the thread take up amount 2 Tighten the screw 7 NOTE If using a thread trimming sewing machine the trailing length for the left upper thread may become shorter after thread trimming because of the twist in the thread The trailing length is normal if the upper thread length is 35 mm w...

Page 75: ... weight materials 405 407 0 70N Adjustment method Thread take up spring R 1 for right thread 1 Loosen the set screw 3 and turn the adjusting thumb 4 to adjust the tension 2 Tighten the set screw 3 Thread take up spring L 2 for left thread 1 Loosen the tension nut 5 2 Use a small screwdriver to turn the tension stud 6 to adjust the tension 3 Tighten the tension nut 5 Measurement method 3017M Do not...

Page 76: ...used and replace it with a thrust ring 4 of the appropriate width Part code Thickness SA4444 001 0 8 mm SA4038 001 1 0 mm S09260 001 1 2 mm When replacing the rotary hook 1 loosen the three set screws 5 Be careful not to lose the thrust ring 4 at this time NOTE There is a piece of felt 7 for lubrication at the base of the rotary hook shaft 6 Gently press down on the rotary hook 1 when tightening t...

Page 77: ...d may be cut too short models with thread trimmer If the clearance is too small The rotary hook may become damaged The opener 1 may become damaged 13 6 Presser foot height 1 Remove the rear cover 1 and remove the rubber cap 2 2 Loosen the nut 3 and loosen the presser adjusting screw 4 3 Use the lifting lever 5 to raise the presser foot 6 4 Loosen the screw 7 and move the presser bar 8 up or down t...

Page 78: ...ise the needle bar 2 until the reference line 8 or 9 depending on the feed condition on the needle bar 2 is aligned with the bottom edge of the needle bar base 4 7 In this condition secure the machine pulley with tape or similar so that the needle bar 2 will not move The procedure up to this point determines the needle bar lift amount NOTE If the needle bar lift amount is too large It will cause p...

Page 79: ...rd while pushing the needle against the rotary hook tip 15 with your finger to make a mark from the rotary hook tip 15 in the hollow of the needle 15 Check that the distance C from the intersection between the mark from the rotary hook tip 15 and the center line of the needle to the top edge of the needle hole is 1 1 5 mm If the distance is not 1 1 5 mm loosen the screw 5 again and adjust the heig...

Page 80: ...ng quick reverse operation distance C for the left needle will become shorter so do not set it to less than 0 7 mm otherwise the rotary hook tip 15 may touch the projection D and this could damage the rotary hook tip 15 16 Loosen the set screw 16 and then pull the needle bar clamp 17 downward to remove it 17 Turn the screw 18 to adjust so that the distance from the upper edge of the needle hole to...

Page 81: ...needle hole in the feed dog 2 The needle will actually be slightly to the front when it goes into the feed dog 2 and will be slightly to the back when it comes out 3 Tighten the screw 1 NOTE Do not overtighten the screw 1 otherwise it will damage the feed rocker base arm 3 Left right position adjustment Adjust so that neither side of the feed dog touches the needle plate 4 when the needle plate 4 ...

Page 82: ...d dog 1 NOTE If the feed dog is too high The feed dog may touch the needle plate The stitch length may become longer than the stitch length dial setting Thread tightening may be poor when using thick threads It may be difficult to obtain uniform stitch lengths for normal feed and reverse feed Lower thread trimming errors may occur models with thread trimmer If the feed dog is too low The stitch le...

Page 83: ...in the feed bar shaft 1 and turn it to make the adjustment 4 Tighten the set screw 5 When the angle of the feed dog is adjusted the forward back position of the feed dog will change Loosen the two screws 7 and adjust the forward back position of the feed dog in accordance with the needle for lower feed in accordance with the needle plate In addition when the angle of the feed dog is adjusted the h...

Page 84: ...hread is not tight Lower thread is not tight y Has the thread been threaded incorrectly If the thread is threaded incorrectly thread it correctly y Is the upper thread tension or lower thread tension too weak Adjust the upper thread tension or lower thread tension y Is the thread take up spring operating range too small Lower the position of the stopper 20 24 51 65 2 Loops appear in seam y Is the ...

Page 85: ...ke up spring tension too strong Reduce the tension of the thread take up spring y Is the thread take up spring operating range too large Raise the position of the stopper y Are the trailing lengths of the upper threads too short after thread trimming Adjust the pretension y Are the threads not being trimmed cleanly Sharpen the fixed knives or replace the fixed and movable knives if necessary y Is ...

Page 86: ...er foot pressure y Is the sewing speed too fast Use the sewing speed control keys to gradually reduce the sewing speed y Is the thread take up amount too small Adjust the thread take up amount 51 51 66 65 52 28 54 7 Material slippage y Is the presser foot pressure too strong Adjust the presser foot pressure 52 8 Lower thread is tangled at the sewing start Spinning of bobbin during thread trimming ...

Page 87: ...it with sandpaper or replace the damaged part y Is the thread take up amount correct Adjust the thread take up amount 18 20 24 9 51 55 65 54 10 Incorrect thread trimming y Is the movable knife damaged or bent Replace the movable knife 11 Broken needles y Is the material being pushed or pulled with excessive force during sewing y Is the needle bent is the needle tip broken or is the needle hole blo...

Page 88: ...wer cord is too long or too many appliances are being run from a single outlet this may cause voltage drops which will in turn cause the reset function to activate and stop the machine even if the power supply itself is normal 27 15 Nothing appears on the operation panel display y Is the power supply connector disconnected from the control box Insert the connector securely y Is operation panel con...

Page 89: ...er OFF switch first E051 The machine head was detected as being tilted back during sewing Turn the power off and then back on again E055 Was the power ON switch pressed while the machine head was still tilted back Press the power OFF switch and then return the machine head to the upright position Is the 14 pin machine connector inside the control box disconnected Press the power OFF switch and the...

Page 90: ... stop position after thread trimming Remove any thread scraps that may be blocking the motor Press the power OFF switch and then turn the machine pulley by hand and check that it turns easily Check that there are no problems with the thread trimming mechanism E130 The sewing machine or motor do not operate when the treadle is depressed Is the 4 pin motor connector inside the control box disconnect...

Page 91: ...no problems with the thread trimming mechanism E410 Error communicating with operation panel Is the 12 pin operation panel connector inside the control box disconnected Press the power OFF switch and then check that the 12 pin operation panel connector is connected to connector P7 on the main PCB 12 E440 Error writing data to main PCB Problem with main PCB Replace the control box E441 Error readin...

Page 92: ...the main PCB This is displayed if the machine pulley moves stiffly when it is turned by hand or if the sewing machine locks up and an abnormal current is flowing Press the power OFF switch and then turn the machine pulley by hand and check that it turns easily This is displayed if there is some problem with the motor and an abnormal current is flowing Replace the motor Problem with control box Rep...

Page 93: ...T 8421C 8422C 8452C 8722C 8752C 15 7 SEGMENT DISPLAY 84 15 7 SEGMENT DISPLAY 4268M ...

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Brother T-8421C, Instruction Manual

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