Brother CB3-B917 Service Manual
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Brother CB3-B917 Service Manual

Brother CB3-B917 Service Manual

Chainstitch button sewer
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SERVICE MANUAL
CB3-B916A
CB3-B917A
Please read this manual before making any adjustments.
CHAINSTITCH BUTTON SEWER
CHAINSTITCH BUTTON SEWER WITH THREAD TRIMMER

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Summary of Contents for Brother CB3-B917

  • Page 1 SERVICE MANUAL CB3-B916A CB3-B917A Please read this manual before making any adjustments. CHAINSTITCH BUTTON SEWER CHAINSTITCH BUTTON SEWER WITH THREAD TRIMMER...

  • Page 2: Safety Instructions

    This service manual is intended for B916A/B917A; be sure to read the B916A/B917A instruction manual before this manual. Carefully read the "SAFETY INSTRUCTIONS" below and the whole of this manual to understand this product before you start maintenance. As a result of research and improvements regarding this product, some details of this manual may not be the same as those for the product you purchased.
  • Page 3 2. Notes on safety WARNING Do not put your hand into any openings near the belt, as your hands could get caught in the belt, and serious injury could result. CAUTION Environmental requirements The ambient temperature should be within the Use the sewing machine in an area which is free range of 5°C to 35°C during use.

  • Page 4: Maintenance And Inspection

    CAUTION Sewing This sewing machine should only be used by When turning the machine pulley by hand in operators who have received the necessary order to check the needle down position in the training in safe use beforehand. hole of the button, turn the pulley until the needle is at the final position after one cycle.
  • Page 5 3. 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. Safety devices: Eye guard, Finger guard, Needle bar cover, Pulley covers,...

  • Page 6: Table Of Contents

    CONTENTS 5. ADJUSTMENTS MECHANICAL DESCRIPTIONS ---------------1 ---------------------------------35 1-1. Start mechanism 5-1. Needle bar height 1-2. Number of stitches changing 5-2. Loop spreader 1-3. Brake mechanism 5-3. Point where needle and looper meet 1-4. Needle bar mechanism 5-4. Clearance between needle bar and looper 1-5.

  • Page 7: Mechanical Descriptions

    1.MECHANICAL DESCRIPTIONS 1. MECHANICAL DESCRIPTIONS 1-1. Start mechanism Lower shaft Drive shaft Clutch assembly 2.Press Stop cam Clutch lever 4.Clutch mounts here 3.Press Pulley Ball bearing 5/16 Ball presser plate 1.Depress pedal 101s Press in with the ball presser plate Clutch connects here 102s CB3-B916A/B917A...

  • Page 8: Number Of Stitches Changing

    1. MECHANICAL DESCRIPTIONS 1-2. Number of stitches changing Number of stitches control lever Number stitches adjustment lever Number stitches 104s adjustment cam Number of stitches 6, 8 105s Number of stitches 12, 16 Stitch 32 lever Roller Number of stitches 106s adjustment gear Number of stitches 24, 32...

  • Page 9: Brake Mechanism

    1.MECHANICAL DESCRIPTIONS 1-3. Brake mechanism Number of stitches control lever 1.Drop Clutch shaft Clutch 3.Clutch released 2.Drop Ball presser plate 108s Ball presser plate Clutch released 109s CB3-B916A/B917A...

  • Page 10: Needle Bar Mechanism

    1. MECHANICAL DESCRIPTIONS 1-4. Needle bar mechanism Needle bar clamp connector Needle bar drive lever 5. Rocking motion 4. Rocking motion Needle bar clamp 6. Vertical motion Needle bar 3. Vertical motion Crank rod Needle Stop cam 1. Rotation 2. Eccentric Pulley 111s 1-5.

  • Page 11: Feed Mechanism

    1. MECHANICAL DESCRIPTIONS 1-6. Feed mechanism 1-6-1. Vertical feed mechanism 116s Feed roller shaft Vertical feed connecting Vertical feed link A 2. Right – left 4. Forward – back Feed bracket Slide block 3. Rocking Feed plate Vertical feed lever Feed roller Vertical feed cam 5.
  • Page 12 1. MECHANICAL DESCRIPTIONS 1-6-1. Horizontal feed mechanism 119s Feed link 3. Rocking Worm Feed bracket Feed roller shaft Feed plate Horizontal feed lever Lower shaft 4. Right - left Feed roller Lower shaft helical gear Vertical feed Drive shaft helical gear Cam shaft 1.

  • Page 13: Thread Trimmer Mechanism

    1. MECHANICAL DESCRIPTIONS 1-7. Thread trimmer mechanism Connecting rod Connecting lever Thread trimming Thread cutter connecting rod lever Pawl Number of stitches adjustment cam 1. Rotation Fixed knife Cam shaft Movable knife 123s Thread trimming lever Number of stitches adjustment lever Number of stitches adjustment cam Number of stitches 6, 8 124s...

  • Page 14: Button Clamp Mechanism

    1. MECHANICAL DESCRIPTIONS 1-8. Button clamp mechanism 1-8-1. Button clamp descent (sewing start) Button clamp lifter Button clamp driving lever Spring Button clamp Button clamp lifter regulating connecting rod plate Button clamp arm assembly Button clamp driving connecting rod Button clamp driving lever Clutch shaft Button clamp Clutch...

  • Page 15: Tension Release Mechanism

    1.MECHANICAL DESCRIPTIONS 1-8-3. Button clamp opener [B917A] Claw adjustment Size adjustment plate plate Button clamp Button clamp opener 130s lever Button clamp opener Button clamp Returns to Button clamp plate cam claw opener lever original 129s position 1-9. Tension release mechanism Disconnects 131s Auxiliary tension (Opens...

  • Page 16: Disassembly

    2. DISASSEMBLY 2. DISASSEMBLY CAUTION Turn off the power switch before starting any Be sure to wear protective goggles and gloves cleaning work, otherwise the machine may when handling the lubricating oil and grease, so operate if the pedal is depressed by mistake, that they do not get into your eyes or onto your which could result in injury.

  • Page 17: Button Clamp

    2. DISASSEMBLY 2-3. Button clamp lifter 1. Spring guide 1. Spring Button clamp 2. Button clamp arm 3. Holder shaft 203s 4. Stud screw 6.35 5. Button clamp lifter arm shaft 204s Button clamp opener claw 6. Button clamp lifter arm Claw adjustment plate CB3-B916A/B917A...

  • Page 18: Looper

    2. DISASSEMBLY 2-4. Looper 3. Loop spreader 1. Feed plate 4. Disconnecting rod 2. Needle plate 206s [B917A] 205s 8. Loop spreader guide [B917A] 5. Movable knife 9. Loop spreader base 6. Fixed knife 7. Needle guard 207s 13. Loop spreader link 12.

  • Page 19: Number Of Stitches Changing

    2. DISASSEMBLY 2-5. Number of stitches changing Number of stitches control lever 8. Number of stitches adjustment cam 7. Thread trimming lever Thrust washer 10. Number of stitches adjustment M gear 3. Number of stitches adjustment gear 9. Snap ring 2.

  • Page 20: Needle Bar

    2. DISASSEMBLY 2-6. Needle bar 7. Tension release rod 5. Spring 6. Adjustment stud 3. Needle bar clamp 1. Needle thread take - up 4. Needle bar clamp connector 2. Needle bar 211s 8. Crank rod upper part 9. Set collar 11.

  • Page 21: Assembly And Adjustment

    3. ASSEMBLY AND ADJUSTMENT 3. ASSEMBLY AND ADJUSTMENT CAUTION Assembly and adjustment of the sewing machine Be sure to wear protective goggles and gloves should only be carried out by a qualified when handling the lubricating oil and grease, so technician.
  • Page 22 3. ASSEMBLY AND ADJUSTMENT 304s 5. With the screw flat of the thread take-up lever shaft facing toward you, pass it through the tension release rod insert into the frame, push lightly, and tighten the screw. 6. Pass the adjustment shaft through the tension release rod and presser driving lever , and then fit the snap ring...

  • Page 23: Number Of Stitches

    3. ASSEMBLY AND ADJUSTMENT 3-2. Number of stitches changing Mark 309s 308s 1. Fit the clutch to the clutch shaft and secure with 2. Rotate the stop cam (pulley) and align the marking on the vertical feed cam with the cam positioning pin the set screw 3.
  • Page 24 3. ASSEMBLY AND ADJUSTMENT 10. Tighten the number of stitches adjustment cam until the clearance between it and the pawl is 0.5 mm. 0.5 mm 312s 11. Attach the spring to the spring hanger and dowel 12. Fit the connecting rod to the connecting rod shaft and attach the ring 313s...

  • Page 25: Loopre

    3. ASSEMBLY AND ADJUSTMENT 3-3. Looper 1. With the reference line of the loop spreader groove cam facing toward you and upward, fit it to the lower shaft , and temporarily tighten in a position 2 mm from the metal piece. Reference Reference line...
  • Page 26 3. ASSEMBLY AND ADJUSTMENT 12. Remove the loop spreader and the loop spreader guide 322s 13. Place the set screw collar onto the looper setting shaft so that the set screw is aligned with the hole, push the looper onto the looper setting shaft as far as it will go, and then provisionally tighten the set screw 323s...
  • Page 27 3. ASSEMBLY AND ADJUSTMENT 14. Align the reference line of the loop spreader groove cam Reference with the looper setting shaft , contact gently, and line tighten. 327s 15. Attach the needle guard to the frame and adjust so that the clearance between the needle and the needle guard is 0.1 –...
  • Page 28 3. ASSEMBLY AND ADJUSTMENT 18. Fit the loop spreader guide to the loop spreader 332s 19. Install the movable knife to the frame 333s 20. Rotate the stop cam to move the sewing machine to the stop position. Contact 334s 21.
  • Page 29 3. ASSEMBLY AND ADJUSTMENT 23. Attach the needle plate to the frame. 24. Temporarily attach the feed plate to the feed bracket 337s 25. Put the sewing machine in the stop position, or align the arrow mark on the vertical feed adjustment lever to the (2 hole) position.

  • Page 30: Button Clamp

    3. ASSEMBLY AND ADJUSTMENT 3-4. Button clamp 1. With the screw flat of the button clamp lifter arm shaft all the way back, pass it through the button clamp lifter arm and then attach it to the button clamp lifter bracket Apply grease 342s 2.

  • Page 31: Clutch

    3. ASSEMBLY AND ADJUSTMENT 3-5. Clutch 1. Tilt the sewing machine downward 2. Turn the spring hanger to adjust so that the distance 10 – 12 mm from the edge of the clutch is 10 – 20 mm. 3. Attach the clutch tension spring to spring hangers 344s 4.

  • Page 32: Cover

    3. ASSEMBLY AND ADJUSTMENT 3-6. Cover 1. Attach the cover to the looper cover 347s 2. Attach the top cover to the frame. (With the top cover on the frame, it will fit well if you pull slider B toward you.) 348s Take-in B Take-in A...
  • Page 33 3. ASSEMBLY AND ADJUSTMENT 4. Attach the face plate and the following parts to the frame. (Face plate thread guard , needle bar cover , face plate thread guide , and sub-tension thread guide 5. Attach the needle 6. Attach the eye guard 352s 7.

  • Page 34: Replacement Of Parts

    4.REPLACEMENT OF PARTS 4. REPLACEMENT OF PARTS CAUTION Assembly and adjustment of the sewing machine If the power switch needs to be left on when should only be carried out by a qualified carrying out some adjustment, be extremely technician. careful to observe all safety precautions.
  • Page 35 4. REPLACEMENT OF PARTS Vertical feed lever 25. Feed roller 27. Worm Horizontal feed lever 26. Feed roller 411s < Assembly and adjustment > 1. The screw flat of the lower shaft should be facing Washer straight downward and the worm tightened temporarily.
  • Page 36 4. REPLACEMENT OF PARTS 6. Place end A of the stop cam side in a vertical position and align the take-in of feed cams with the cam positioning pin . Tighten the stop screw at the side of direction of rotation to the screw flat of the cam shaft .
  • Page 37 4. REPLACEMENT OF PARTS 10. Tighten the button clamp driving lever temporarily so that the clearance between the button clamp driving fork and the driving link , and between the driving link and the vertical feed cam , is 1 mm. 11.
  • Page 38 4. REPLACEMENT OF PARTS 18. Insert the brake shaft into the hole in the bed. 19. Insert the brake lever shaft into the oval hole in the brake lever , and provisionally tighten the set screw on the bottom side of the clutch body 20.

  • Page 39: Cushion Rubber

    4. REPLACEMENT OF PARTS 4-2.Cushion rubber 3.Ball < Disassembly > presser plate 5.Steel ball 5/16 1.Bolt 6.Pulley 7.Steel ball 7/32 2.Open the cover 8.Pulley return spring and tilt the sewing machine 428s 9.Clutch 4.V-belt tension spring 406s 11.Cushion rubber 10.Clutch plate 431s Use a screwdriver to pry 430s...

  • Page 40: Driving Lever Pawl

    4. REPLACEMENT OF PARTS 4-3.Operating lever pawl < Disassembly > 1.Bolt 2.Open the cover and tilt the sewing machine downward. 3.Put the machine into 4.Operating lever pawl 428s the start condition. 436s < Assembly > 1. Attach the operating lever pawl to the connecting rod assembly With the sewing machine in the start condition, install so...

  • Page 41: Adjustments

    5.ADJUSTMENT 5. ADJUSTMENT CAUTION Assembly and adjustment of the sewing machine Be sure to wear protective goggles and gloves should only be carried out by a qualified when handling the lubricating oil and grease, so technician. that they do not get into your eyes or onto your skin, otherwise inflammation can result.

  • Page 42: Movable Knife

    5. ADJUSTMENT 5-7.Movable knife 5-8.Number of stitches control lever 0.5 – 1 mm Clutch Roller Fixed knife Number of Connecting stitches adjustment Movable lever knife 0.5 mm 335s Number of stitches 425s adjustment Connecting lever 336s Start the sewing machine by pressing the rear part of the Adjust the connecting rod so the boss A on the movable knife clutch.

  • Page 43: 5-12.Worm And Worm Gear Backlash

    5. ADJUSTMENT 5-12.Worm and worm gear backlash 5-13.Pulley clearance in thrust direction Ball presser plate Pulley Approx. 0.3 mm 0.8 mm Horizontal feed cam Clutch plate Tighten Screw Loosen Worm Worm gear 424s 346s The clearance between the pulley and the clutch plate should Adjust the feed cam to obtain a backlash of approximately 0.3 be 0.8 mm.

  • Page 44: 5-15.Auxiliary Tension Timing

    5. ADJUSTMENT 5-15.Auxiliary tension timing 5-16.Thread tension timing Slow Quick Needle bar loosening loosening Auxiliary TQx1 45 mm tension 0.5 mm 10 mm TQx7 508s 507s B917A With the machine in the start condition, the tension discs While the needle bar is raised and the reference line of the should be 0.5 mm apart.

  • Page 45: 5-19.Button Clamp Installation

    5. ADJUSTMENT 5-19.Button clamp installation 5-20.Elevation amount of button clamp Button clamp regulating plate Button clamp Button clamp 13 – 14 mm Feed plate 513s 514s Place the button on the button clamp and set the scale of the The distance between the upper part of the feed plate and the horizontal feed and the vertical feed to the distance between tip of the button clamp should be 13 –...

  • Page 46: 5-24.Button Clamp Opener (B917A)

    5. ADJUSTMENT 5-24.Button clamp opener (B917A) 1. When the pulley is turned and, at the final stitch, the Button Button clamp Roller clamp lifter lever and the roller contact, adjust the lifter lever Contact adjustment plate so that the button clamp opener claw B contacts the button clamp open lever at the same time.

  • Page 47: 5-27.Rotor

    5. ADJUSTMENT 5-27.Rotor Fig. A Fig. B Take-in Decrease Increase Thread remainder at first stitch Thread missed at first stitch Rotor 520s 521s 522s The standard position of the rotor is the position where, with the machine stopped, the 1.5 mark (B917A) is aligned with the take- For B916A, it is where the 2 mark is aligned with the take-in.

  • Page 48: Troubleshooting

    6. TROUBLESHOOTING 6. TROUBLESHOOTING Problem Cause Solution Page 1. Broken Tension is too strong. (1) Loosen the tension control nut on the main crossover stitch tension. (2) Lower the auxiliary tension control. B917A - 45 mm B916A - 46 mm TQx1 601s TQx7...
  • Page 49 6. TROUBLESHOOTING Problem Cause Solution Page 2. Thread frays at Thread take-up lever pulls too much Raise the thread take-up lever to decrease the final stitch thread. amount of thread taken in. (B917A) Stitch is normal. Thread frays between thread tension and material.
  • Page 50 6. TROUBLESHOOTING Problem Cause Solution Page 4.Thread breaks Inconsistent thread looping due to (1) Use a platform feed plate. bunching of material. Thread frays and breaks. Thread breaks at different 612s points. Thread breaks (2) Increase the button clamp pressure. and stitch skips simultaneously...
  • Page 51 6. TROUBLESHOOTING Problem Cause Solution Page 7.Thread remains Needle catches the stitch behind the (1) Move the loop spreader away from the needle. in loop on odd material, preventing thread tightening. stitches 603s (4-hole) (2-hole) A frays appears in the loop. Occurs with 0.3 –...
  • Page 52 6. TROUBLESHOOTING Problem Cause Solution Page 11. Stitches skip Insufficient needle thread length (1) Decrease the thread cutter lever to stitch at sewing start control cam gap when the machine is in the stop position. 624s (4-hole) 0.5 mm 626s 627s (2) Decrease main tension control setting.
  • Page 53 6.TROUBLESHOOTING Problem Cause Solution Page 12. Final stitch Looper misses thread. Refer to “11.Stitches skip at sewing start” . skips 631s Approx. Approx. Occurs together Approx. 45 mm with thread cutter 20 mm 20 mm Link skipped Needle thread errors. Link skipped Stitch comes out Thread cut cleanly...
  • Page 54 6. TROUBLESHOOTING Problem Cause Solution Page 15. Thread parts Thread splits on material top. (1) Increase the sub tension. at stitch link 639s 606s Thread winds (2) Use a finer thread. onto looper in machine stop (3) Decrease the number of stitch. position.
  • Page 55 6. TROUBLESHOOTING Problem Cause Solution Page 17. Clutch does Motor is not turning fast enough for the Use a standard pulley. not engage. needle bar to advance to the stop 50Hz-----N75 pulley (Machine position (standard motor speed is 1500 60Hz-----N65 pulley stops before rpm).
  • Page 56 SERVICE MANUAL NAGOYA, JAPAN 118-916/917 Printed in Japan I0070790 2000.07. F (1)

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