When was the last time your quilt block was the exact size it was supposed to be? If your blocks are off a bit, perhaps it’s time to re-check your seam allowances.
Cut three strips of fabric, 1-1/2″ wide. Stitch them side-by-side, using your best 1/4″ seam. Press seam allowances away from center strip. Now, measure the center strip. Is it exactly 1″ wide? If it isn’t, you aren’t sewing an exact 1/4″ seam, and need to make adjustments.
By the way – just what is a “scant 1/4″? It’s a 1/4” seam that’s just a thread or two less than a true 1/4″. So it really isn’t a 1/4″. Want more information? Read about it on Diary of a Quilter.