Have you ever wondered why your quilt block does not measure the size it is supposed to be? Here may be the answer – If you were to sew your block with an exact 1/4” seam, it is going to be a little smaller than the correct size. A scant 1/4” seam is just shy by just a few threads, and in the process of piecing your quilt block that is important. Because, once you sew the seam and press it, the piecing thread and the fold from pressing will replace the thickness of a few threads. Voila – you now have a block to measure correctly. Using a fine 50 weight thread such as Aurifll will also help to get those seams correct. If you are using a heavier fabric or thread, you may have to adjust the size of your seam allowance too. The 1/4” foot that attaches to your machine may not always be correct. If you have a machine that your needles moves right or left, try that to get it correct also. If you are off that tiny 1/8” and you have 4 seams in your block, you could be off 1/2" in your finished block size. Small errors add up, especially if you have a lot of seam. So the hint is – Always test your 1/4” seam before you start a new project. You will thank yourself!!
How to test your seam allowance for accuracy
Cut three 1 1/2” x 3 1/2” strips of fabric. Sew the strips together along the long edge with a scant 1/4” seam allowance. Press the seam allowances towards the center strip. The center strip should now measure exactly 1”. The three pieces together should measure 3 1/2” square. If it does not, you will need to adjust your guide and retest again. Practice makes precision piecing and be patient; it will pay off in the end.