Understanding Quilt Block Patterns

Sewing Half-Square Triangles

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.

As a review: Methods 1 and 2    Methods 3 and 4

Method 5 – Bias Strips = Half-Square Triangles
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.

Step 1 – 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……..

Step 2 – With the right sides of the fabric facing each other, sew a ¼” seam along both sides of the strip.

Step 3 – Press the strips to set the seams.

Step 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.

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.

Step 5 - Open each half-square triangle, and press (preferable press the seam allowance so it is under the darker fabric).

Step 6 – Trim the “dog ears” off of the edges of the squares.

Method 6 – Two Large Rectangles = Multiple Triangles

Using this method, you will cut large, but manageable rectangles, mark sewing and cutting lines, sew them, and then cut the triangles.  The preparation/marking time is less than if you were marking each square separately.  The sewing time also is less since there is only one unit of fabric to handle instead of individual triangles.

Step 1 – Determine how large to cut the rectangle pieces of fabric.  To determine the cut size, take the finished size and add ⅞” to both sides.  For example, if you are using 2” squares (finished size), the cut size will be 2⅞” square. 

Figure out how many of these squares you would like to have on your fabric.  Using the above example, 6 squares across would require a 17¼” length, and 4 squares down would require a 11¼” width of fabric.  This configuration would result in 24 squares of half-square triangles.  You may wish to add extra on each of the sides.

Step 2 – On the wrong side of the lighter fabric, draw the cutting lines of your squares.  Using the same example, mark 24 squares that measure 2⅞ ” each.  Then draw a diagonal line through the center of each square.  This, too, is a cutting line.

Step 3 – Place the fabric right sides together (one marked and the other one not marked).  Sew each of the squares two times, ¼” on each side of the diagonal line through the center of the square.

Step 4 – Press the sewn rectangle to set the stitching.  Cut on the drawn lines to make your triangles.

First, cut the lines to make strips.

Once you have strips, cut them apart into squares.

And, finally, cut the squares apart, making triangles.

Step 5 - Open each half-square triangle, and press (preferable press the seam allowance so it is under the darker fabric). 

Step 6 – Trim the “dog ears” off of the edges of the squares.

Spider Quilt Block This 4 patch, two color quilt block is made with simple half-square triangles placed in different directions in the block. If I were sewing this block, I would use a speed method of sewing the patches together. Spider Quilt Pattern This 9 patch two color block is made of half-square triangles as well. As you can see, by changing the direction of the patches, you will create a completely different look. In this case, both this and the block to the left have been named Spider - although the designs are completely different. Beginner's Delight Quilt Block This easy-to-make, 5 patch is made from two different sizes of half-square triangles. The larger half-square triangles in the center create a pinwheel, and the small half-square triangles around the outside frame the center pinwheel. The QuiltBlockLibrary.com offers a variety of Four Patch, Five Patch, Seven Patch, and Nine Patch Patterns, with suggested color variations. While it is not necessary to stick with the suggested colors, maintaining the placement of dark, light and medium fabrics will allow you to retain the traditional design of the quilt block.     If you aren't already signed up to receive this series of emails:   Sign up for the weekly How-to-Quilt.com Newsletter Get Great Quilting Tips and Ideas for Quilts Name Email: (required) Peaceful Piecing! www.QuiltBlockLibrary.com www.How-to-Quilt.com www.TheQuiltingCoach.com   Web www.How-To-Quilt.com