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Possible Problem Area
Solution Checklist
Rotary hook
1. Check the hook timing and the needle gap; one (or both) may be
out of adjustment.
2.
Check to make sure the rotary hook is rotating smoothly & suffi
-
ciently oiled.
If it is not, clean, oil, and if the problems persist, replace.
If you are still experiencing thread breaks after checking all of the areas discussed in the above table, you
may want to perform a more in-depth analysis. This analysis involves sewing out the test design.
From the beginning of the test, if the problems are addressed as described below, their frequency should
become much less as you continue the test. (Note: the most challenging is the small lettering; quite of-
ten, resolving thread breaks in this area will solve any thread break problems.) As you sew the test design,
use the following table to troubleshoot problem areas.
If thread breaks
occur when
sewing:
Check the following items:
Horizontal or verti-
cal bars at startup,
or soon after (also
called miss-starts).
• Hook timing and needle guard gap
• Make sure tail length (length of thread tail left after a trim) is adequate
• Make sure that thread is being held in trap (in grabber assembly) during
trims
• Check the under thread presser spring
• Inspect thread feeder rollers & pinch rollers for wear and/or damage
At the startup of
the small lettering
• Hook timing
Small lettering
(after startup)
• Needle depth
• Hook timing and needle gap
• Needle orientation
• Make sure the needle plate is centered
• Inspect thread feeder rollers & pinch rollers for wear and/or damage
Triangles & Fill
• Hook timing. Hook timing is the most frequent cause of thread breaks in
this area
• Inspect thread feeder rollers & pinch rollers for wear and/or damage
At the startup of
the circles
• Needle gap
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