Brother HE-800B, Service Manual

Page: 113 / 178

7. ADJUSTMENT
HE-800B
104
7-13. Adjusting the lower thread trimming
7-13-1. Adjusting the lower thread trimmer fixed knife engagement amount
1. With the power turned off, move the lower thread trimmer cam lever (1) in the direction of the arrow so that the knife driving
lever (2) is in the position shown in the illustration.
2. Check that the cam A of the movable knife (3) is sitting securely on top of the cam B of the base plate (4).
3. Loosen the two screws (5), and then adjust so that the fixed knife (6) and the movable knife (3) are engaged by
approximately 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.
7-13-2
.
Adjusting the lower thread retaining amount
1. Turn on the power and set the sewing machine to the home position.
2. Loosen the two screws (1), and then adjust the lower thread retainer (2) 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 (3) 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 not being pulled out of the
lower thread clamp plate (3), and that it is not too loose when it is coming out from the bobbin case.
If the lower thread retaining amount is too small
The lower thread will pull out of the lower thread clamp plate 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.
If the lower thread retaining amount is too great
This can cause problems such as poor sealing at the sewing start, or wound lower thread sticking out of the rear tack.
4343Q 4342Q
4345Q 4344Q
Approx.
1 mm
Lower thread trimming complete
Smaller
Larger
1 – 2 mm