You put the top and bottom fabrics over each other, flatten them, and start cutting. Once you get to the final corner, the bottom fabric has moved just a couple of millimeters. You try to sew the two pieces, but they don’t line up, even though you cut both from the same pattern. This problem is common with small accessories like tote bags, since seams tend to be short, there’s an exposed zipper area, boxed corners, and linings that require precision to align properly.
The reason layers shift during sewing or cutting is because the layers aren’t moving as one piece. The upper layer slides over the lower layer, the lower layer stretches as it moves, or the fabric gets raised as you cut it. Even a stable cotton can shift if there aren’t enough pins or weights to hold it in place. This problem is even worse when there are multiple layers of fabric or when the fabric is dragged across the table during cutting or sewing.
To avoid shifting when cutting, make sure your fabric is properly supported while cutting. Make sure that the grainline is straight before starting to cut, and smooth out all layers of the fabric to avoid any stretching. Use enough pins or weights to hold the fabric in place. If you’re using scissors, keep the blade close to the cutting surface while cutting to minimize the fabric from being raised. A rotary cutter and cutting mat can help prevent shifting when cutting woven fabrics, as the fabric remains flat during the cut, although it should still be secured to avoid shifting.
It’s also possible that the fabric shifted when sewing. When you place two layers of fabric right sides together, the presser foot and feed dogs might not move the top and bottom layer of fabric at the same speed. As a result, the bottom layer of fabric might move faster than the top layer, causing one edge to be longer than the other. It’s helpful to pin or clip the fabric together to prevent this shifting. If you’re working on a seam that needs to be precisely aligned, such as a zipper area or a curved section, basting may be a better option than pinning, as it will allow you to control the fabric better.
Hand placement can also cause shifting while sewing. If you pull the fabric from the back of the presser foot, or push the fabric towards the needle, the seam will distort and the edge will stretch. Instead, lightly guide the fabric and let the machine feed it. Instead of trying to control the fabric at the needle, watch the seam guide or the raw edge. If the fabric layers start to separate, stop sewing, leave the needle in the fabric, lift the presser foot, realign the fabric, and continue sewing instead of continuing to sew misaligned fabric.
A great way to practice proper alignment without worrying about ruining a project is to cut several pairs of small squares from your scrap fabric. Then mark each pair at corresponding points along the edges, place the right sides together, and secure one pair with two pins, one pair with several pins or fabric clips, and one pair with a row of basting. Sew each pair using the same seam allowance. Afterward, check the edges to see which technique resulted in the least amount of shifting. This will help you determine which method will work best for your fabric, and how much shifting occurs when sewing different fabrics.
Before progressing to the next step of your construction process, make sure to check for a gradual shift between the matching edges rather than checking only the corners. If a lining edge, zipper edge, or side seam starts out lined up but finishes noticeably shifted, figure out why and fix the problem before trimming or turning the fabric. One of the easiest ways to achieve cleaner textile construction is to ask yourself, “Are my fabric layers still in the same spot?”