I have a 1/4 inch foot for my Janome. It isn't exactly 1/4 inch. I found out it wasn't exact when I made a circle quilt. Luckily I figured it out early in the project. I can move my needle position a couple of clicks to make it exact. I now check it from time to time and it hasn't changed. I am taking my machine in for a tune up tomorrow and will check it again when I get it back. Can you move your needle to make a perfect 1/4 inch with your foot?