-38-
7.
TIMING OF NEEDLE AND ROTARY HOOK ASSEMBLY
(CLEARANCE BETWEEN THE NEEDLE AND THE ROTARY HOOK POINT)
STANDARD
For left straight line sewing, the rotary hook assembly point and the needle outer edge should match when the
needle rises 2.9-3.3 mm from bottom dead center. The clearance between the rotary hook assembly point and
the routing surface of the needle (#14) at this time should be no greater than 0.15 mm on both left and right and
the rotary hook assembly point should not touch the needle.
ADJUSTMENT
1.
Turn the selection dial, turn the Zigzag dial, to the maximum and set to left straight line sewing.
2.
Loosen the three screws securing the lower shaft gear.
3.
Align the position of the rotary hook assembly. (Adjust so that the rotary hook assembly point matches the
outer edge of the needle when the needle rises 2.9-3.3 mm from bottom dead center.)
4.
Tighten the three screws securing the lower shaft gear.
5.
Turn the selection dial to select zigzag sewing.
6.
Turn the adjustment screw so that the clearance between the rotary hook assembly point and the routing
surface of the needle at this time is no greater than 0.15 mm. Check that for both the left and right needle
descent positions, the needle does not touch the rotary hook assembly point.
Adjustment Points
If there is a difference in the clearances between the rotary hook assembly point and the routing surface of the
needle at the left and right needle descent positions, loosen the needle bar block shaft A set screw and adjust
the needle bar block assembly left-right position to eliminate the difference left and right.
∗
If the clearance is larger at the right needle descent position.... Move the needle bar block to the left.
∗
If the clearance is larger at the left needle descent position ...... Move the needle bar block to the right.
*
If the needle adjustment is inadequate, the following problems may occur.
1.
If the clearance is too large, skipped stitches may occur.
2.
If the clearance is too small, the needle may generate an irregular noise (scraping metal sound) or the
needle may break.
3.
If the needle rises too little, skipped stitches, split thread, or cut thread may occur.
4.
If the needle rises too much, skipped stitches, split thread, or cut thread may occur due to a loop forming
in the thread.
*
Before adjusting the needle and rotary hook assembly timing, execute 4. NEEDLE DOWN POSITION
ADJUSTMENT, 5.NEEDLE FLOW and 6. LEFT STRAIGHT LINE SEWING NEEDLE DESCENT AND
ZIGZAG MAXIMUM LEFT NEEDLE DESCENT.
(BL6300)
(BL6800)
Needle bar block shaft A
set screw
0.5 mm
max.
0 mm
2.9-
3.3 mm
