Inspect the Unit and its Seams
- Were seam allowances pressed adequately? It's easy to "lose" width in patches that aren't fully pressed. Press again and recheck.
- Make sure aligned strip edges didn't shift away from each other when you sewed the seam. If they did, try placing a very warm iron on top of the patches before sewing to help them stick together or secure edges with very fine straight pins before sewing. Remove pins as the needle approaches.
- Are the seams irregular, wide in some spots and narrow in others? Sew more slowly to improve accuracy. Set the machine to run on half speed if possible.
Sew another set of strips, then press and measure. If dimensions are still not accurate, don't worry, you'll get there with a few more changes.
Cut several more 2" wide strips of fabric to use in test units.
Change Needle Position
Change the needle position if your sewing machine allows it. Move the needle a notch to the right if you must shorten the seam allowance. Move it to the left if you must increase the allowance.Sew another test set, again aligning the fabric with the right edge of the presser foot. Press and measure. If seams are still not accurate you can place a seam guide on your sewing machine's throat plate.
Before you add an extra guide, look at the grooved lines on the throat plate to see if there's one located 1/4" to the right of the needle. Sew another test strip, aligning edges to that line. Press and measure.
