Brother LH4-B800E Service Manual download pdf (Page 106)

LH4-B800E

4 - 19

4. Adjustment

(A)

(B)

1 mm

(A)

(B)

(A)

(B)

1 - 2 mm

4-14. Adjusting the lower thread trimming

4-14-1. Adjusting the lower thread trimmer fixed knife engagement amount

Lower thread trimming complete

1. With the power turned off, move the lower thread trimmer cam lever q in the direction of the arrow so that the knife

driving lever w is in the position shown in the illustration. Check that the cam (A) of the movable knife e is sitting

securely on top of the cam (B) of the base plate r.

2. Loosen the screw t, and then adjust so that the fixed knife y and the movable knife e are engaged by approxi-

mately 1 mm.

* If the engagement amount is too small, the lower thread may not be fully cut, and the material may get caught

when it is removed after sewing.

4-14-2. Adjusting the lower thread retaining amount

Smaller

Larger

1. Turn on the power and set the sewing machine to the home position.

2. Loosen the screw q, and then adjust the lower thread retainer w to a distance of 1—2 mm as shown in the

illustration.

* If the lower thread retaining amount has been reduced, check that the roller (B) of the lower thread clamp plate e

is sitting securely on top of the lower thread retainer cam (A).

* If the lower thread is pulling up at the first stitch at the sewing start, check if the lower thread is being pulled out of

the lower thread clamp plate e, and that it is not too loose when it is coming out from the bobbin case.

The lower thread will pull out of the lower thread clamp plate e at the first stitch at the sewing start, which can

cause problems such as lower thread cast-off, lower thread loops or poor lower thread winding.

This can cause problems such as poor sealing at the sewing start, or wound lower thread sticking out of the rear

tack.

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Brother LH4-B800E Service Manual Page 106