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hand sewing

How to Sew Set-In Seams by Machine and Hand for Quilt Blocks

Set a square or triangle into a quilt block by marking matching seam-line dots and stitching each edge only between its endpoints.

By ThatPainter Team 3 min read
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To sew a set-in seam without stitching into the seam allowance, mark the seam-line endpoints and sew each adjoining edge only from dot to dot. In quilt piecing, a set-in square or triangle fills an opening where the surrounding pieces cannot be joined with continuous straight seams. The same endpoint rule applies whether you sew by machine or by hand.

Mark the seam endpoints first

On the wrong side of each piece, mark the matching inner and outer dots on the seam line. The American Patchwork & Quilting Editors’ example uses a 1/4-inch seam line. Accurate matching dots identify the corners and show exactly where each seam segment must begin and end.

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If you are using a template, an optional marking aid is to pierce its dots with a large needle or awl, then mark through the holes with a fabric pen or pencil.

Sew a set-in seam by machine

  1. Pin the first two pieces together, matching their dots, and sew from dot to dot. Press the pieces open.
  2. Match the first-and-third-piece corners and dots. Sew from the inside-corner dot to the outer-edge dot.
  3. Bring the square’s adjacent edge up to the next edge of the opening. Match the corners and dots, then sew from the inside corner to the outer edge.
  4. Press the unit open. Set in a triangle in the same way as a square.

Secure a seam that starts away from an edge

When a machine seam begins at a dot rather than at the fabric edge, secure its start: sew forward a couple of stitches, take a couple of backstitches, then continue to the opposite edge or dot. Stop at the marked endpoint; do not sew through the corner into the seam allowance.

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Sew a set-in seam by hand

The hand method below joins a square into the opening formed by two pieced diamonds. Use hand-sewing needles; no particular brand or model is required.

  1. Put the pieces right sides together. Align one edge of the diamond unit with an edge of the square and match the points. Hand-stitch from the open end toward the inside corner, beginning and ending at the matching points. Remove pins as you sew.
  2. At the inside corner, backstitch to secure the seam, but do not cut the thread. Keep the seam allowances free of stitching. As the American Patchwork & Quilting Editors explain, “They are not sewn down as they are in machine piecing.”
  3. Bring the square’s adjacent edge up to the adjoining edge of the diamond unit. Match the points, pin the rest of the seam, and stitch from the corner toward the open end. Stop at the matching point, backstitch, and trim the thread, leaving a short tail.
  4. Press the square’s seam allowances toward the diamonds and press the diamonds’ joining seam to one side. Set in a triangle in the same manner.

Check the corners before pressing

  • Check that the marked corners meet.
  • Check that stitching stops at the dots, without crossing into the seam allowance.
  • For hand sewing, check that the inside corner is secured and that the seam allowances have not been stitched down.

If the unit does not lie as intended, recheck the point alignment and seam endpoints before suspecting the machine or needle. Matching and stopping at the dots are the key controls in this technique.

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Quilt set-in seams are not garment set-in sleeves

This method is for setting a square or triangle into a quilt block. A garment set-in sleeve is a separate pattern piece joined to a bodice armhole, often with ease in the sleeve cap; it uses a different construction procedure.

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