Thanks for all that replied. Upper tension adjustment took care of my problem of thread bunching up on the bottom of my fabric. I used two different colors and confirmed that the loose upper tension was allowing oodles of extra thread to collect and jumble at the bottom of the seam row.
New tension problem!!! While I have found a sweet spot for the upper tension adjustment that allows me to sew 2-4 layer of vinyl, after about
10-12 inches of stitches the thread breaks. It is totally jammed tight between the upper tension discs. I am assuming that the thread is supposed to ride between the discs bearing all the way down on the shaft that supports the discs. Or, is it supposed to ride up near the outside of the discs the way a belt and pulley would ride? In any case, when my thread breaks, the thread is all the way against the shaft and it's almost impossible to manually pull on either side of the thread. The shaft is smooth and not notched or grooved in any manner. Should I oil this bearing surface?BTW, I've been adjusting the tension by placing the thread between the discs and pulling at it from both ends until it 'feels' right. Then I sew about
3-4 inches and check the stitches to see if they are centered in the fabric. Having done all of this I start sewing, great results, and then, all of a sudden the discs decide to grab my thread and, naturally, sewing comes to an end.All advice appreciated.
Ivan Vegvary