I am thinking that a seam guide might just work for this if it is a metal one. Your would have to slow down and just touch the tip with your iron, or possibly use an applique iron, but it should work for you to get a perfect measure along the seam.
I just realized something. The seam is 1/4 (or 1/2) inch in the middle, but the ends at the beginning stay pretty flat to join correctly on a cathedral window quilt. It makes it look like a circle when they are all joined together.
Last edited by RedGarnet222; 02-14-2014 at 06:45 PM.