Needle And Rotary Hook Timing Adjustment; Needle To Rotary Hook Point Gap; Needle Bar Rise And Height - Brother b831 Service Manual

[H NEEDLE AND ROTARY HOOK TIMING ADJUSTMENT
* Be sure to check the position detector ad)ustment (p.43) after the needle and rotary hook timing is adjusted.
1. Needle to rotary hook point gap
Needle q-O 05 mm
Rotary hook point
Needle guard
0.05 mm
0—0.15 mm
®
0]
About 0.2 mm
1. Loosen the screws ®. ® and ©, and move the rotary-hook base O to the right or left untilthe clearances between the
needles and rotary-hook tips are about 0.05 mm.
2. Adjust the engagement ofthespiral gearO by adjusting the clearance between theinner sideofthe rotary-hook base O
and the end face of the spiral gear O to about 0.2 mm by moving the spiral gear O to the right or left.
* Tighten the screws © for the spiral gear O in such a way as not to change the contact.
* The needle guard on the rotary hook is to prevent needle to rotary hook point contact. Be sure to readjust the needle
guard position when the rotary hook is replaced.
2. Needle bar rise and height
* Needle bar rise specifications vary with different models. Use the following table to adjust the rise. The gap between
reference marks is 2.4 mm.
Models-B831 6832 B835 6836 B882
Model
Rise
Feed dial
Application
Standard
Thread cutter
Standard Thread cutter
Thin materials
Synthetic threads 2.6 mm
—
2
—
118-831
Regular materials 2.4 mm
•
2
• ~
Thick materials
2 4 mm
3
Thin materials
Synthetic threads 2 6 mm
2
118-832
Regular materials 2.4 mm
2.4 mm 2
0
Thick materials
2.4 mm
2.4 mm 3 0
118-835
836
Regular materials 2 4 mm
2.4 mm 3 0
118-882
Regular materials 2.4 mm
3
Needle bar rise should be set to 2 4 mm on machineswith which a thread cutter is used.
When adjusting the walking bar feed regulator dial on model B831. press the feed regulator button and align the
machine pulley scale with the red dot.
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