Straight, even topstitching comes from following a guide, not from a steady hand: use an edgestitch foot, a quilting guide bar or a line of tape on the needle plate so that the fabric edge runs along something fixed, lengthen the stitch to 3 to 3.5 mm, use a topstitch needle one size larger than for the seam, and sew at a slow, constant speed without stopping on curves. Press the seam first and start every row from the same end, and two parallel rows will stay parallel.

What is topstitching and what is it for?

Topstitching is a visible row of stitches sewn from the right side of the garment, parallel to a seam or an edge, usually 6 mm (1/4 in) or more from it. It holds seam allowances and facings flat, strengthens seams that take strain, and decorates: the two rows on a jeans seam, the stitching around a collar, the line along a pocket edge.

Edgestitching is topstitching sewn very close to the edge, 1 to 3 mm (1/16 to 1/8 in) from it. The two are often used together: a row of edgestitching plus a row of topstitching 6 mm away is the classic jeans and shirt finish.

Because it is on the outside, every wobble shows. The methods below remove the causes of wobbles one at a time.

What do you need to topstitch well?

  • A guide. An edgestitch foot (also sold as a stitch-in-the-ditch foot) has a blade in the center that rides along the edge or the seam; move the needle position to set the distance. A quilting guide bar clips to the foot for rows further from the edge. Failing both, a strip of masking tape or a magnetic seam guide on the needle plate.
  • A topstitch needle: 90/14 for medium fabrics, 100/16 for denim and canvas. Its larger eye and deeper groove carry thick thread without shredding it.
  • Thread. Regular polyester thread for a quiet finish, or topstitching thread (about three times thicker) for the heavy, contrasting look. Use topstitching thread on top only, with regular thread in the bobbin.
  • A stitch length of 3 to 3.5 mm (up to 4 mm on denim). Longer stitches lie straighter and show the thread off; short stitches look nervous.
  • Pressed seams. Topstitching does not flatten a lumpy seam; it fixes the lumps in place.

How do you topstitch straight step by step?

  1. Press the seam or edge in its final position, and let it cool. On a faced edge, understitch first so the seam sits exactly at the edge.
  2. Fit the guide. Snap on the edgestitch foot, or set the tape on the needle plate at the distance you want, measured from the needle with a ruler. For a row 6 mm (1/4 in) from the edge, the edge of a standard foot is often exactly 6 mm from the center needle position; check with a ruler on your machine.
  3. Choose the needle position. With an edgestitch foot, move the needle left or right so the stitching falls the distance you want from the blade. Note the setting so a second row matches.
  4. Set the stitch length to 3 to 3.5 mm and, if you are using topstitching thread, loosen the top tension slightly and test on a scrap of the same number of layers.
  5. Start with the thread tails held behind the foot and the first stitch 2 to 3 mm in from the edge; do not backstitch on visible topstitching. Pull the tails to the wrong side at the end and tie them off, or sew the first and last few stitches at a 1 mm length to lock them.
  6. Watch the guide, not the needle. Keep your eyes on the fabric edge where it meets the foot's blade or the tape, about 1 cm (3/8 in) ahead of the needle. Your hands make small corrections there; by the time fabric reaches the needle it is too late.
  7. Sew at a slow, constant speed. Variation in speed is what shows as a wobble. Use the speed limiter if your machine has one, or set your foot and leave it.
  8. Do not stop on a curve. Slow right down and keep the fabric turning smoothly with your fingertips. If you must stop, stop with the needle down, lift the foot, turn a few degrees, and continue.
  9. Pivot at corners with the needle down. Sew to the pivot point, needle down, foot up, turn, foot down. For a sharp outer corner on thick fabric, take one stitch across the corner at 45 degrees instead of a true pivot; it looks sharper from the outside.
  10. Sew every parallel row from the same end, in the same direction, with the same guide setting. Rows sewn in opposite directions drift apart because the fabric feeds a little differently each way.
  11. Cross thick seams with a hump jumper, a folded scrap of fabric or a piece of card placed behind the foot, so the foot stays level as it climbs. A tilted foot skips stitches and veers.
  12. Press the finished row from the wrong side, then from the right side through a cloth.

Which foot gives the straightest topstitching?

The edgestitch foot for anything within about 8 mm (5/16 in) of an edge or a seam. For rows further in, the quilting guide bar or tape. On knits, vinyl, oilcloth and anything that creeps, a walking foot with the guide bar keeps the layers moving together. A clear foot, with no metal in the way, helps on curves. The presser feet post shows what each one looks like.

What are the most common topstitching mistakes?

  • Watching the needle. It is the one place where you cannot correct anything. Watch the guide.
  • Using the seam needle. An 80/12 universal shreds topstitching thread. A topstitch needle with its long eye is the fix; the needles and thread guide lists sizes by fabric.
  • A short stitch. At 2.5 mm the thread sits in the fabric and every tiny wobble shows. Lengthen to 3 to 3.5 mm.
  • Backstitching. It leaves a knot of thread on the outside. Lock the ends with a short stitch length or tie them off at the back.
  • Topstitching thread in the bobbin. It jams most domestic machines. Top only, regular thread in the bobbin.
  • Starting the second row at the other end because it was nearer. It will not be parallel.
  • Stopping and starting on a curve. Each restart leaves a small angle. Slow down instead.
  • Unpressed seams. A seam allowance that has flipped under the stitching makes a ridge the needle climbs and falls off. Press, then stitch.

When should you topstitch instead of leaving the seam plain?

Topstitch when the allowance needs holding down (facings, yokes, a pressed-to-one-side seam on a jacket), when the seam takes strain (jeans, bags, workwear), and when you want the lines to show. A flat-felled seam is topstitching and seam finish in one. Patch pockets are attached entirely by topstitching, and on heavy fabrics such as denim the double row is both the look and the strength.

Leave it plain on fine fabrics where the stitching would pucker, on garments where you want a soft, uninterrupted surface, and on seams that will be pressed open. Where you want the holding without the visible line, stitching in the ditch hides the stitches in the seam.