I know I'm not the only one to struggle with this. I always avoided block swaps because I wasn't sure I could turn out accurate blocks, and the stress was just too much for me. Once I hosted a project where everybody made some blocks for a quilt. I supplied the background material, so I know it was all cut right (or at least consistently wrong – kidding, my cutting skills are actually pretty good). One woman's blocks were all too small. In keeping with the generous nature of a quilter, I went to her house to help her figure out the problem. She showed me her whole set up. I showed her how her quarter inch seam was actually wider than a quarter inch, which resulted in her blocks turning out too small. She just looked at me blankly and finally said she'd just keep her blocks and make more because her blocks all fit together just fine. Okaaaay.
Then a very generous quilter sent me some paper and plastic measurement thingies to help me measure an accurate quarter inch seam. I was very grateful to her, but because at that point I was still not clear on adjusting the needle placement (that came later), I couldn't get it to work consistently and so I was too stressed to join in her block swaps. But not for long!
I've pondered and played with the foot issue on my sewing machine from the start. My machine came with a handful of feet, and I've purchased a handful more, all in the quest of the perfect quarter inch seam. I have finally achieved it, and this is my story...
Then, just to keep life interesting, every so often I'd feel the need to do a zig zag stitch and wouldn't change the foot. Problem! This made the needle hit the edge of the foot. It gradually chipped away the plastic on the right edge until I *could* do a zig zag with this foot. But then one day the right edge broke off, and there I was, with no good quarter inch foot.