How to Sew Set-In Seams By Machine and Hand
With set-in seams, the piece to be added is stitched into the unit in two steps. Diamond blocks frequently contain set-in squares and triangles. Joining stitches for these pieces run from marked dot to marked dot and do not extend into seam allowances.
Transferring Dots to Fabric Pieces
To ensure that the pieces fit together accurately, the pattern templates should have dots marked on the 1⁄4" seam line at the outer and inner corners. To transfer those dots to the fabric pieces, first pierce a small hole through each dot on the template with a large needle or awl. Make sure the hole is just large enough for the point of a fabric pen or pencil. Align the template over the wrong side of the fabric piece and mark through the holes.
Starting a Set-In Seam by Machine
Seams that begin away from the fabric edge need to be secured with a few backstitches.
Begin sewing forward at the dot for a couple of stitches, take a couple of backstitches, and continue sewing to the opposite edge or dot. Avoid the urge to backstitch too far. You do not want to go past the starting point. Too many layers of thread will add unnecessary bulk to the finished seam. Stitching forward, backstitching, and stitching forward again gives the beginning part of the seam three layers of thread.
1. Turn your work so the starting dot is 1⁄4" in front of the needle. Stitch forward to the dot.
2. Leaving the needle in the fabric, pivot the work 180º and continue sewing the seam. With this method, there are only two layers of thread in the beginning part of the seam.
Ending a Set-In Seam by Machine
Seams that end away from the fabric edge need to be secured with a few backstitches.
Stop sewing forward at the dot and take a few backstitches.
1. Stop sewing forward at the dot. Leave the needle in the fabric at the dot and pivot the work 180º.
2. Take a couple of stitches forward on top of the previous stitching.
Assembling a Set-In Seam by Machine
1. Mark joining dots at the 1⁄4" seam lines on the wrong side of each piece at the outer and inner corners.
2. Pin and sew together the first two pieces, starting and stopping at the dots. Press the pieces open.
3. Matching the corners and dots of the first and third pieces, pin and sew from the dot at the inside corner to the dot at the outer edge.
4. Bring the edge of the second piece up and align it with the adjacent edge of the third piece, matching corners and dots, and sew from the dot at the inside corner to the dot at the outer edge.
5. Press the unit open. Sew a set-in triangle in the same manner as a set-in square.
Assembling a Set-In Seam by Hand
The following instructions describe how to set a square into the opening left by two pieced-together diamonds.
1. With right sides together, pin one edge of the two-diamond unit to one edge of the square, aligning matching points. Hand-stitch the seam from the open end of the diamond into the corner, beginning and ending at the matching points and removing pins as you sew. Backstitch at the inside corner to secure, but do not cut the thread. Note: Keep seam allowances free of stitching. They are not sewn down as they are in machine piecing.
2. Bring the adjacent edge of the square up and align it with the adjacent edge of the diamond unit. Insert a pin at aligned matching points, then pin the remainder of the seam line. Hand-stitch the seam from the corner to the open end of the angle, removing pins as you sew. Do not sew past the matching points at the end. Backstitch to secure the seam. Trim thread, leaving a short thread tail.
3. Press both seam allowances of the set-in square toward the diamonds; press the diamonds' joining seam to one side. Sew a set-in triangle in the same manner as a set-in square.