Brother b831 Service Manual page 23

Thread Trimmer Adjustment (Opener)
0.2 mm
1.0~1.5 mm
2.4 mm
Procedures
1. Turn the machine upright,
2. Set the feed regulator dial to 0.
3. When needle O rises 2.4 mm from its lowest point, align rotary hook point O with the centerof needle O (right and
left).
(Loosen the pinion screw and adjust by turning the rotary hook.)
4. Install the throat plate with screw O and screw 0.
5. Temporarily install bobbin case opener 0 with flat screw O and washer 0 (right and left).
6. Adjust so that the clearance between the rotary hook and bobbin case opener 0 is 0.2 mm with screw ©when bobbin
case opener 0 is fully pulled back in the arrow direction (right and left).
Procedures
7. Loosen screw 0, remove screw O. and remove throat plate 0.
8- Turn the machine over.
9. Remove knife return spring 0 (right and left).
10. Turn the machine upright
11. Temporarily fasten movable knife ® with screw o and screw
12. When bobbin case opener 0 is fully pulled back, adjust so that the clearance between the tip of movable knife ® and
rotary hook position bracket is 0.05~0.2 mm with screw O and screw ® while pressing the upper face of movable
knife ®.
13- Install throat plate 0 with screw O and screw 0
14. Install knife return spring 0.
• If stud screws are unfastened, fixed knives will be removed.
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