Slider Adjustment; Bobbin Thread Clamp Spring - Brother b831 Service Manual

[§ SLIDER ADJUSTMENT
1. Slider
Bobbin thread clamp spring
Lever L
Lever R
Connecting rod
0.3~0.5 mm v
0.3~0.5 mm
Movable knife return spring ^ ^
Bobbin thread clamp
1) Remove the bobbin thread clamp spring.
2) The slider O toslider base O gap should be 0.3 to0.5 mm when the movable knife O is worked back and forth with
the movable knife rocker arm O- (The slider O should not strike the slider base O )
3) Loosen set screw 0. and adjust the forward/back position ofthe movable knife rocker arm O.
2. Bobbin thread clamp spring
If the thread end is not clamped lightly on horizontal
rotary hook machines, stitch formation at the beginning
of sewing is not possible. The bobbin thread clamp
spring O is provided on this machine to hold the thread
end.
The bobbin thread clamp spring O should be installed
directly below and slightly to the side of the movable
knife.
Note: Be careful th clamping area of the bobbin thread
clamp spring O does not touch the rotary hook
or feed dog.
BB Insufficient bobbin thread clamp spring tension
• Stitches will be skipped at the beginning of sewing when a heavy thread is replaced with a light thread.
BB Excessive bobbin thread clamp spring tension
• Several stitches will be skipped at the beginning of sewing.
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