5-22
5) Relationship between the Take-up Lever and the Hook
Hook point timing is directly related to thread tension and thread breaks. The following pictures show the location
of hook when the take-up lever starts to move up from the lower dead stop (main shaft rotation angle: 291
�
).
Groove of the hook is in the (A) range. The
hook point will take up the thread when the
loop is too small. Stitching will be faster
than the take-up movement. As a result, the
thread tension will be too loose, upper
thread loop will be too small, and skipped
stitches will occur.
[CAUTION]
In normal hook timing, the hook should be in the (C) range as shown in the picture below.
Fast Hook Timing
Slow Hook Timing
[Fig.5-33]
too small
too large
[Fig.5-34]
[Fig.5-35]
(B)
(C)
(A)
Groove of the hook is in the (B) range. The
hook point will take up the thread when the
loop is too large, so there may not be
skipped stitches. However, the take-up
movement will be faster than the stitching
and thread breaks may occur.
