Adjusting The Needle Bar Height; Adjusting The Needle And Rotary Hook Timing - Brother LH4-B800E Service Manual

4. Adjustment

4-4. Adjusting the needle bar height

w
r
Turn on the power and set the sewing machine to the home position. Then press the RESET key to lower the presser
foot.
1. Move the needle bar q to its lowest position. (Check that the needle is in the center of the needle hole. If adjust-
ment is necessary, make the adjustment while referring to "4-1. Adjusting the needle zigzag home position sensor
position".)
2. Remove the rubber cap w from the face plate, and then loosen the set screw e of the needle bar clamp.
3. Insert the "1" part of the gauge r between the needle plate t and the lower edge of the needle bar q, and move
the needle bar q so that it touches the gauge r.
* Different gauges are used for each of the three sub-classes -2, -3 and -5, so make sure that the gauge being
used matches the specifications and application for the sewing machine being adjusted.
4. Tighten the set screw e.
5. Install the rubber cap w.
* Check that the knife flank of the needle bar is at a right angle to the knife. If the installation positions are not
correct, the needle bar and knife may touch when the needle zigzags, which may result in noise or cause the
needle to break.

4-5. Adjusting the needle and rotary hook timing

o
q
Turn on the power and set the sewing machine to the home position. Then press the RESET key to lower the presser
foot.
1. Loosen the two set screws w of the rotary hook joint q.
2. Turn the machine pulley in the regular direction of rotation (toward the front) so that the needle bar e just begins
to rise from its lowest position.
3. Insert the "2" part of the gauge r between the needle plate t and the lower edge of the needle bar e, and then
align the rotary hook point y with the center of the needle when the needle bar contacts the gauge.
* Different gauges are used for each of the three sub-classes -2, -3 and -5, so make sure that the gauge being
used matches the specifications and application for the sewing machine being adjusted.
4 - 6
e
q
t
r
0.01 - 0.08 mm
i
u
w
Needle bar
O.K.
NG
e
LH4-B800E
0.3 mm
y
t
Cutter
Lowest
position