Brother LH4-B800E Service Manual page 107

4. Adjustment
4-14-3. Adjusting the lower thread clamp opening timing
t
t
Sewing start
t
Carry out the adjustment in "4-2. Adjusting the feed home position sensor position" before carrying out this adjust-
ment.
1. Loosen the set screw w of the feed arm support q, and then align reference line A of feed guide shaft B e with
the edge of the feed arm support q. When the feed mechanism moves by 6—7 mm, the opening plate r moves
and the lower thread lamp t opens. To change the opening timing, loosen the set screw w and move feed guide
shaft B e to the left or right.
The end of the thread which is being held by the lower thread clamp t is wound around inside the seam. If the
*
opening timing is too early, it can cause problems such as poor winding or pulling-up of the lower thread. If the
opening timing is too late, it can cause problems such as stretching, uneven seams or bird's nests at the sewing
start, depending on the type of material.
4 - 20
r
6 - 7 mm
Lower thread winds around seam
r
w
w
Lower thread releases from lower thread clamp
LH4-B800E
q
e
Reference line A
q
e