By Chris Sharp, MFC
Cracks in the glass are caused by:
- Not cutting deep enough before bending
- Sewing through a scratch made by the razor blade; never cut paper away while still on the glass; always fold paper to cut away
- Excessive back tacking
- Allowing too much motion on high stress points
Before sewing the first panel, make up a mock panel using the same materials. As you sew this piece, adjust the tension of the thread to get thread “knot” in center of the glass. If the tension is too tight, the thread will constantly break and the stitching will skip.
Another cause of skipped stitches is a buildup of adhesive and the AR coating. Clean the needle and shuttle hook when changing the bobbin. If using metal bobbins, put a drop of oil under the bobbin. Spray some silicone on top of the bobbin case. This will help reduce friction and skipped stitches.
Stitching at full speed will cause too much friction and lead to thread failure. Half machine speed works the best.