Baby Lock Jewel Service Manual
© Baby Lock, all rights reserved
33
Skipped Stitches
Proper Stitch formation:
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The needle goes down through the fabric to its lowest position.
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The needle is the proper size for the fabric being sewn and the thread being used.
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The needle has a long groove down the front and an eye that fits the thread
appropriately. The bigger the needle the bigger the long groove down the front of the
needle and the bigger the eye of the needle.
•
The fabric presses the top thread against the back of the needle but not at the front
because the long groove protects the thread in the front.
•
The hopping foot holds the fabric down firmly as the needle rises to form the loop.
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The top thread is pressed to the back of the needle by the fabric when the needle
rises slightly. The top thread then forms a loop on the back of the needle, using the
principle of friction.
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The hook rotates into the top thread loop just formed and continues to rotate as the
top thread goes across the hook and bobbin case and is wrapped around the bobbin
case thread.
•
The take up lever then pulls the excess top thread back up completing the stitch.
•
Proper tension settings on the bobbin case (bottom thread) and the top tension
assembly (top thread) along with a little help from the take up spring, insure the stitch
is balanced and locked in the fabric.
•
When the stitch is locked in the fabric properly it will be strong and nice looking
because the knots will be locked up in the fabric with proper friction.
Four major causes of skipped stitches:
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Improper loop formation: out of time, poor friction due to slippery fabric and or thread,
poor friction due to wrong size needle for fabric and thread – needle makes too big of
a hole to have proper friction for stitch formation, fabric trampolines due to hopping
foot being set too high, – loop does not form.
•
Improper loop position: out of time, needle installed improperly eye rotated, needle
installed improperly too low.
•
Improper hook position: out of time, improper distance between needle and hook,
damaged hook or broken hook point.
•
Improper needle position: out of time, improper needle bar height setting, bent needle,
wrong needle system, improper needle position setting.
More Causes of Skipped Stitches:
•
If one moves too fast, too slow or too broad it can cause skipped stitches even if
everything else is correct. This happens because the needle is deflected by the
operator while in the quilt fabric and this effectively changes the timing between the
hook and the needle.
•
Too much tension can cause skipped stitches – even if top and bottom are balanced.
•
Tensions that are too loose can cause skipped stitches – as well as thread locks.
•
If the tensions are too imbalanced, then one thread will be straight with no knots in the
fabric and therefore there will be no fabric friction between each stitch. This makes it
possible to pull the straight thread out of the fabric because of no friction on the thread
at each stitch knot.