How to finish seams without a serger

You can finish seams beautifully without a serger. The quickest finish is a zigzag stitch along each raw edge; pinking shears suit stable fabrics that barely fray; and for a clean inside, enclose the raw edges with a French seam on light fabrics, a flat-felled seam on sturdy ones, or a Hong Kong finish on unlined jackets. Choose by the weight of the fabric, how much it frays, and whether the inside will be seen.

Which seam finish should I use?

All of these work within the 1.5 cm (5/8 in) seam allowance that most woven patterns use, Sewly's included, so you do not need to change the pattern.

Seams pressed open or to one side?

Decide before you finish. A seam pressed open (allowances spread flat on either side) is finished on each allowance separately, either before you sew it or straight after. A seam pressed to one side is finished with both allowances together after sewing, usually trimmed to about 1 cm (3/8 in) first. French and flat-felled seams always lie to one side. Whatever you choose, finish each seam before another seam crosses it, or the ends become unreachable.

Zigzag or overcast finish

1. Set a zigzag stitch about 4 mm wide and 1.5 to 2 mm long.
2. Sew along the raw edge of the allowance so the right-hand swing of the needle lands a hair off the edge, or exactly on it. The thread wraps the edge and holds the fabric threads in.
3. If the fabric tunnels (rolls up into a ridge under the stitch), sew the zigzag 6 mm (1/4 in) in from the edge instead and trim close to the stitching afterwards.
4. If your machine has an overcast stitch and an overcast foot, use them: the foot has a small guide that keeps the edge flat.

This is the finish to use on curves such as armholes and crotch seams, where the others are fiddly.

Pinked finish

Cut along the raw edge with pinking shears, taking off as little as possible. The zigzag edge resists fraying on stable cottons and wool. For more security, sew a straight line 6 mm (1/4 in) from the edge first, then pink.

Turned and stitched (clean finish)

Press the raw edge of each allowance 3 to 6 mm (1/8 to 1/4 in) to the wrong side and edgestitch it 1 to 2 mm (1/16 in) from the fold. Neat and durable on light cottons and linens; too bulky on thick fabrics and awkward on tight curves.

French seam

A French seam encloses the raw edges inside a narrow tube. With a 1.5 cm (5/8 in) allowance:

1. Place the pieces wrong sides together, the opposite of a normal seam, and sew 6 mm (1/4 in) from the edge.
2. Trim the allowance to 3 mm (1/8 in). Press it to one side, then fold the fabric along the seam so the right sides are together, and press the fold sharply.
3. Sew 1 cm (3/8 in) from the fold. The raw edges are now trapped inside.
4. Press the finished seam to one side, usually toward the back.

In imperial the arithmetic is exact: 1/4 in plus 3/8 in makes 5/8 in. In metric, 6 mm plus 1 cm makes 1.6 cm, close enough to 1.5 cm on most garments. If threads poke out after the second seam, trim the first one closer next time.

Flat-felled seam

The strongest finish, used on jeans and shirts. Both raw edges are enclosed and the seam is stitched flat to the garment.

1. Sew the seam at 1.5 cm (5/8 in). Sew it right sides together if the felled side should be inside, wrong sides together if it should show outside, as on jeans.
2. Trim one allowance to 6 mm (1/4 in).
3. Fold the wider allowance in half over the trimmed one, tucking its raw edge under, and press.
4. Press both toward the trimmed side so the folded edge lies flat on the garment, and pin.
5. Edgestitch along the fold, 1 to 2 mm from it. From the right side you see two parallel rows of stitching.

A felling foot does steps 3 to 5 faster on long straight seams. See flat-felled seam.

Hong Kong finish

Each allowance is wrapped in a strip of light bias fabric, so the inside of an unlined jacket looks as good as the outside.

1. Cut bias strips 2.5 to 3 cm (1 to 1 1/4 in) wide from a light fabric such as cotton lawn or lining.
2. Sew the seam and press it open.
3. Sew a strip to the edge of one allowance, right sides together, 6 mm (1/4 in) from the edge.
4. Wrap the strip around the raw edge to the underside and press.
5. From the top, stitch in the ditch of the first seam to catch the strip underneath. Trim the excess strip close to the stitching; bias barely frays.

Bias-bound seam

The same idea with a folded binding: double-fold bias tape slipped over each raw edge, or over both together, and edgestitched. It is quick with ready-made tape, and the bias binding calculator tells you how much to make from a square of fabric.

Pressing the finished seam

Press after each finishing step, at the right heat for the fiber: about 200 °C (390 °F) for cotton and linen, 150 °C (300 °F) with a press cloth for wool, silk and viscose, 110 °C (230 °F) for polyester. Pressing flat after the first pass of a French or flat-felled seam is what makes the second pass accurate.

What about knits?

Knits do not fray, so they do not need a finish to survive. A narrow zigzag along both allowances together keeps them flat and tidy through washing. Avoid French and flat-felled seams on stretchy knits: the extra rows of straight stitching cannot stretch with the fabric.

Common mistakes and fixes

• The zigzag rolls the edge into a ridge. Stitch slightly in from the edge and trim, narrow the stitch, or use the overcast foot.
• French seam whiskers on the right side. The first seam was too wide or not trimmed enough. Unpick the second seam, trim to 3 mm (1/8 in), and sew it again.
• A stiff, bulky flat-felled seam. The fabric is too thick for felling. Use a zigzag finish pressed to one side with a row of topstitching instead.
• Pinked edges fraying in the wash. The fabric frays more than expected. Add a straight stitch 6 mm (1/4 in) from the edge, or zigzag over the pinked edge.
• An unreachable seam end. The seam was crossed before it was finished. Finish what you can reach, and stitch the short remaining bit by hand with an overcast stitch.

If you are not sure which finish suits a step, ask the guide that comes with your Sewly pattern: it answers about your pattern and your fabric. For the stitching itself, see how to sew a straight seam.