The seam begins to drift, so your hand reaches forward to yank it back. For a moment you think you’re helping. Then the fabric stretches, the seam slants, and the raw edges no longer line up as neatly as they did before stitching began. Straight seams aren’t made by pulling fabric through the machine. They’re made by gently guiding the fabric through while the feed dogs and presser foot do the rest.
Sewing machines are designed to move fabric forward at a set speed. Pulling from the back of the machine can bend the needle, make stitch length uneven, and even stretch delicate, thin fabrics. Pushing the fabric from the front of the machine might make it fold or ripple, especially in long seams like side seams, or hems, or anywhere two pieces of fabric are sewn together so the raw edges stay aligned throughout the entire seam. Your hands guide and don’t dictate speed.
Before sewing together the parts of a garment, sew some test pieces first. Cut two long rectangles from woven fabric. Place the rectangles right sides together and pin or clip along the cut edges. Mark where your sewing will start with a bit of tailor’s chalk, or line up the edge of the fabric with your sewing machine’s seam guide, if one is available. Start with a small backstitch to anchor the stitches in place, then place both hands either side of the fabric. Watch the raw edges of your fabric meet the guide, don’t stare just at the needle.
If the seam starts to go off course, stop the machine while the needle is still down. Having the needle down acts as an anchor, and keeps your seam line steady as you make adjustments. Only lift the presser foot if you need to loosen or turn the fabric to make a slight adjustment. Lower the presser foot again before continuing to stitch. Don’t move the fabric sideways with the needle up, or you’ll create a jagged bend in your seam. A straight seam can and should have multiple stops and starts, it isn’t a race!
The speed of your machine can have more of an effect than you might expect. Sewing too fast can mean you won’t notice the raw edges drifting away from the seam guide. Speed can also make it hard to take out misplaced pins before reaching the presser foot. Sewing at a more moderate pace gives you time to remove your pins as they come to the edge of the presser foot, to smooth out layers of fabric as you go, and to check that the two pieces of fabric stay perfectly matched in width at the seam edge. If your machine has speed control, start with a low setting. If it doesn’t, practice pressing down gradually until you develop a rhythm of slow and even movement.
How the fabric is managed before the sewing even begins makes a huge difference. If you have pinned the seam with pins only along the ends, it can be tempting to start stitching, only to have the top layer of fabric slide forward as you go. Adding more pins, or clips, in between the ends, especially in longer seams, can help keep the fabric pieces in place as you stitch. If your project uses fabric that easily shifts, or slides, consider basting the two pieces together before the final stitching. Once you’ve finished sewing, see whether the two raw edges stayed even, or if they were perfectly matched all along, or at least in a few places. Seeing this can tell you more than a quick once-over looking at the seam from across the room.
Sewing a straighter seam is a much more peaceful experience. You can let the fabric move smoothly through the machine; you don’t have to tug at it or force it into place. The raw edge of the fabric will hover near the seam guide, and the needle will not have to catch and rescue a drifting seam. The next time you sew a test seam, look around at your hands as you stitch. Where they’re tense, you are probably pulling the fabric too hard. When that happens, you are more likely to sew an unflatteringly wavy or uneven seam. Slow down, relax and guide the fabric instead.