Hi there I am just getting into sewing as a hobby and would like to make some bags for my sailboat out of various heavy materials among other small projects. A friend of mine gave me what I believe is a singer 111w155 (the label has been removed). I had to do a bit of research to figure out how to retime the machine, it was 1 tooth off on the timing belt. I set needle height and all that according to the manual, and got it sewing.
The problem I am having is I can't seem to get enough top tension, no matter what I do. According what I've been reading, I have too loose top tension or too tight bottom tension. I have tried every combination from having the top tention loose to all the way tight, and same thing with the bottom tension. I tried every combination from tight to loose enough for the spring screw to fall out (luckily I found it in the carpet). I still get the same results. The top stitch looks ok most of the time from above, bottom stitch is loose and can see the top stitch poking through to the bottom.
I am new to sewing but I have worked as a machinist for 10 yrs, so not new to precision mechanical stuff. I have checked and rechecked that I'm threading the machine correctly, and using new needles. I have gotten the machine to make a few good looking stitches, but then I change nothing and make another stitch on the same material and it's all screwed up. The material I have been sewing is some pvc coated fabric I used to make covers for my milling machine, it was all I have on hand before I order something else.
I have searched a fair amount and cant seem to find anybody else with the same issues. I am guessing I need some new parts, or I'm missing some other adjustment. Anybody have any ideas? Thanks!