I used to think that my 1/4" seam was accurate and consistent. I was sure of it, because when I did my first (and second) - a 4 patch - everything lined up nicely. Came to find that they were consistent, yes...consistently bigger than a 1/4"! Learned that one doing warm wishes, where my strip blocks were consistently smaller than my square blocks!! There was a lot of trimming and ripping going on...but I learned how to line up my seams BEAUTIFULLY!! I finally took a hint from here and stuck some painter's tape on my machine as a 1/4" guide and I'm working on a D9P, and oh the ease and glory and wonderfulness of consistent 1/4" seams!! :D