Timing Between The Needle And The Hook - JUKI HZL-NX7 Service Manual

6-8 Timing between the needle and the hook

○ Remove the throat plate, the bottom cover A/B and the bottom cover of the free arm.
Method for checking
1. Check to be sure that the needle entry point and needle bar height are correct.
2. Select the straight stitch. Select the right needle position by using the zigzag width adjusting dial.
(The needle entry point is shifted to the rightmost side.)
3. Now, turn the hand wheel by hand to bring the needle bar to its lowest dead point.
4. Turn the hand wheel further to gradually lift the needle bar until point C where the needle center is aligned
with the tip of blade point of the hook is reached.
5. At this time, check to be sure that the distance D from the tip of blade point of the hook to the upper end
of the needle eye is 3.1 to 3.3 mm. If this distance is not correctly provided, carry out the following adjust-
ment.
Adjustment procedure
1. Loosen the setscrew in the hook driving gear which is not visible from underside of the sewing machine
when the needle center aligns with the tip of blade point of the hook.
2. Select the straight stitch and the right needle position. Move the hook driving gear in the rotational direc-
tion to adjust distance D of 3.1 to 3.3 mm is provided between the tip of blade point of the hook and the
upper end of the needle eye when the needle bar is lifted by 1.6 mm from the lowest dead point by turning
the hand wheel by hand.
At this time, the backlash between the hook driving gear and the gear on the hook side may change de-
pending on the location of the hook driving gear on the hook driving shaft. Adjustment should, therefore,
be carried out with the visible setscrew temporarily tightened, while carefully observing the hook driving
gear in both the rotational direction and axial direction. Adjust the backlash to 0.2 to 0.7 mm on the periph-
ery of the rotating hook.
3. After confirming the timing between the needle and hook is correctly adjusted, securely tighten both set-
screws.
(Caution) After adjustment of the hook, the hook race surface and the bobbin case holder may be stained
with dirt, oil or grease. Wipe them off with alcohol where necessary.
If those parts are left stained, chattering or thread slip-off noise of the bobbin case holder can
occur.
C
Backlash on the periphery of the
rotating hook 0.2 to 0.7 mm
– 20 –
Larger
Backlash
Rotating
hook
Hook
driving
gear
Smaller