SunStar HC Series User Manual page 34

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:
292°).
Fast Hook Timing
too small
Slow Hook Timing
too large
[CAUTION] In normal hook timing, the hook should be in the (C) range in the picture below.
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.
[Fig.4-26]
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.
[Fig.4-27]
[Fig.4-28]