SunStar SWF/B Series User Manual page 37

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.
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.
[CAUTION]
In normal hook timing, the hook should be in the (C) range as shown in the picture below.
too small
too large
(B)
Hook groove
(C)
(A)
5-19
Fast Hook Timing
Slow Hook Timing
[Fig.5-34]
[Fig.5-35]
[Fig.5-36]