How to Sew Half-Square Triangles (Method 5 of 6)

The half-square triangle is a basic piece used in many quilt blocks. Very simply, it is a square that is cut in half from corner to corner (diagonally) to create two triangles within one patch.

As amazing as it sounds, there are several ways to sew these units together. Some of these methods increase the accuracy of the resulting patch (for example Methods 2 and 4). Other methods increase the speed or convenience of sewing many half-square triangles (Methods 5 and 6).

Which method you use depends upon personal preference.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Fabric
• Thread
• Sewing Machine or Needle
• Scissors or Rotary Cutter
• Ruler

1. 

   Using this method, you will cut strips of fabric on the bias, sew the edges, and then cut the strip, making your squares. Using this method, you will sew strips on the bias, taking care not to stretch the fabric as you sew. There is no marking using this method, unless you mark your cutting line instead of just using the rotary cutter and ruler.
   
   This method is a little more complex than some of the others, and does result in some wasted fabric pieces.
   
   Determine the size of the strips to cut, and then cut them. Using the example of a 2” finished size square, each strip will be cut 1⅞” wide. If the finished size is a 3” square, each strip will be cut 2¾” wide. For other sizes, you may need to experiment; or if you know the math……..

2. 

   With the right sides of the fabric facing each other, sew a ¼” seam along both sides of the strip.

3. Press the strips to set the seams.

4. 

   This step is easiest if you have a plastic square to use with your rotary cutter. If you don’t, you can measure and mark the fabric and then cut.
   
   Place the square ruler on the strip of fabric so that the diagonal part of the ruler is lined up with the side of the strip.
   
   Check to see that the seam allowance is the correct distance from the edge of the ruler where you will cut. If you are cutting a 2” finished size square, the edge of the ruler should be 2” away from the seam allowance. This is a little tricky, since you are measuring at a 45° angle. Once you have done it a couple of times, you will get the hang of it.

5. 

   Once you have cut one triangle set out, turn your fabric (or ruler) around to cut the other side of the strip. You will be cutting these triangle units in a flip-flop manner to minimize the wasted fabric. Following the pictures will be helpful.

6. 

   Open each half-square triangle, and press (preferable press the seam allowance so it is under the darker fabric).

7. Trim the “dog ears” off of the edges of the squares.

Resources

• How To Quilt
• Quilt Block Library