The term '1/4 inch' seam is both a misnomer & a moving target. It's misnamed because you don't measure the
seam, you measure the
resultant patch. Here's a good way to check:
http://www.quiltingboard.com/tutoria...ce-t89997.html
It's a moving target because different fabric and thread combos can make the seam placement different on different projects. Some folks are lucky with their 1/4" foot because it is positioned correctly for their fabric & thread choices. I have to move my needle position to get the seam where it needs to be, and if I use different thread or fabric, I recheck at the start of the project and adjust the needle position if needed. It only takes a couple minutes. Once you figure out where the seam should be, you may find that the foot guide isn't going to work, or your machine has a fixed needle position then you need to use a piece of tape or magnetic guide to create the correct seam.