Inspect the strips carefully if they are not the correct size:
- 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 next set of patches before sewing to help them stick together, or secure their 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, and then press and measure. If dimensions are still not accurate, don't worry, you'll get there with a few more changes.
Consider Changing the Needle Position
- Cut additional 2" wide strips of fabric.
- Change the needle position if possible. 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 presser foot as described on page 2. Press and measure. If seams are still not accurate you can place a seam guide on your sewing machine's throat plate, next page.