To sew a straight seam, pin the two pieces right sides together, line their edges up with the 1.5 cm (5/8 in) mark on your machine's throat plate, and stitch at a 2.5 mm length while watching the fabric edge against that mark, not the needle. Backstitch three or four stitches at each end. To turn a corner, stop with the needle down exactly on the corner point, lift the presser foot, pivot the fabric, lower the foot and carry on.
Set up the machine
- Needle: a universal 80/12 for medium woven cotton and linen, a 70/10 for lawn and voile, a 90/14 or a denim needle for denim and canvas. Put in a new one if you cannot remember the last time you changed it.
- Thread: a good all-purpose polyester, the same in the needle and the bobbin.
- Stitch: straight stitch, length 2.5 mm (about 10 stitches per inch). Use 2 mm (about 12 per inch) on very fine fabrics and curves, and 3 mm (about 8 per inch) on thick layers.
- Test: sew a seam through two layers of a scrap of your fabric. Both sides should look the same, with no loops and no puckering. If not, see sewing machine basics for threading and tension.
Find your seam guide
The seam allowance is the distance between the fabric edge and the stitching. Most woven patterns use 1.5 cm (5/8 in); Sewly patterns use 1.5 cm on wovens and 1 cm (3/8 in) on knits by default, and draw the sewing line as a dashed line on each piece so you can see where it falls.
Look at the metal throat plate to the right of the needle: engraved lines mark distances from the needle, often in both millimeters and eighths of an inch. Find the one you need. If there is none, measure 1.5 cm from the needle and stick a strip of masking tape there, as long as possible so the fabric edge rides along it well in front of the foot. Magnetic seam guides are handy too, but check your machine's manual before putting a magnet near a computerized machine.
How to sew a straight seam, step by step
- Pin right sides together. Match the ends and the notches first, then pin in between every 8 to 10 cm (3 to 4 in), pins at right angles to the edge with their heads toward you.
- Position the fabric. Place the edge on the guide line, with the needle about 1 cm (3/8 in) below the top edge.
- Hold the threads. Hold both thread tails lightly behind the foot for the first few stitches. This stops them being pulled down into a tangle under the fabric.
- Lower the foot and backstitch. Sew three or four stitches forward, three or four in reverse back to the top edge, then forward again. This locks the seam. See backstitch.
- Guide, do not push. Rest your hands flat on the fabric, in front of and to the left of the foot. Let the feed dogs pull it through; your hands only steer. Keep your eyes on the fabric edge and the guide line, not on the needle.
- Remove pins before they reach the foot. Sewing over pins can bend or break the needle and knock the seam off line.
- Finish. At the bottom edge, backstitch three or four stitches, sew forward again to the edge, raise the needle and the foot, and pull the fabric away toward the back. Cut the threads, leaving about 1 cm (3/8 in).
- Press. Press the seam flat as sewn to set the stitches, then press it open or to one side as the pattern says, from the wrong side.
How to pivot at a corner
- Mark the pivot point with a dot 1.5 cm (5/8 in) from both edges, where the two sewing lines cross. On patterns that draw the sewing line, such as Sewly's, it is the corner of the dashed line.
- Sew toward the corner and slow down for the last 2 cm (3/4 in). Turn the handwheel by hand for the last stitch or two so the needle goes down exactly on the mark.
- With the needle down in the fabric, lift the presser foot.
- Turn the fabric around the needle until the next edge lines up with the seam guide.
- Lower the foot and carry on sewing.
- Before turning the piece right side out, cut the corner off diagonally, 3 mm (1/8 in) from the stitching, so the point turns out sharp instead of lumpy.
For a very sharp point, such as the tip of a collar or a tie, take one or two short stitches straight across the corner instead of a single pivot. It leaves room for the allowances inside and gives a crisper point once turned.
How to sew a curved seam
Shorten the stitch to 2 mm, sew slowly, and turn the fabric gradually so the edge keeps the same distance from the guide. On tight curves, stop every few stitches with the needle down, lift the foot, turn slightly and lower it again. Afterwards, clip or notch the allowance so the curve lies flat: straight clips on inward curves, small wedges on outward curves, stopping 2 mm (1/16 in) from the stitching.
Pressing temperatures by fiber
Pressing every seam before crossing it with another is half of what makes a garment look professional.
| Fiber | Iron setting | Steam | Notes |
|---|---|---|---|
| Linen | Three dots, about 200 °C (390 °F), or the linen setting | Plenty | Press while slightly damp |
| Cotton | Three dots, about 200 °C (390 °F) | Yes | Press cloth on dark colors to avoid shine |
| Wool | Two dots, about 150 °C (300 °F) | Yes | Always use a press cloth |
| Silk, viscose | Two dots, about 150 °C (300 °F) | Light | Press cloth, from the wrong side |
| Polyester, nylon | One dot, about 110 °C (230 °F) | Little | Test first: synthetics can melt or turn shiny |
Practice drills
- Draw straight lines 1.5 cm apart on sheets of paper and sew along them with no thread in the needle. The holes show exactly how straight you are.
- Draw a square spiral on paper or a scrap and sew it, pivoting at every corner.
- Sew two pieces of striped fabric together along one stripe.
- Make a cushion cover: four straight seams and four corners, with a result you will use.
Common mistakes and fixes
- The seam wanders. You are watching the needle. Watch the fabric edge on the guide, and sew more slowly; speed comes later.
- A thread nest at the start. The presser foot was up when you started, or the thread tails were not held. Cut the nest out from the underside, rethread the top thread with the foot up, and start again holding the tails.
- Puckered seam. Stitch too short for the fabric, or tension too high. Lengthen to 2.5 to 3 mm and test on a scrap.
- The layers end up uneven. The top layer creeps forward. Pin more often, reduce the presser foot pressure if your machine allows it, or use a walking foot.
- Skipped stitches. A blunt or wrong needle. Change it and check it is pushed all the way up, flat side to the back on most home machines.
- Fabric pulled into the needle hole. Thin fabric gets pushed down at the start. Start 1 cm (3/8 in) in from the edge, or start on a small folded scrap and sew straight off it onto your seam.
Once your seams are straight, finish the raw edges so they do not fray: see finishing seams without a serger.