Tuesday, March 15, 2016


If I were still teaching school, I would explain to my students that a half-square triangle (HST) was simply a square made from two isosceles right triangles. They are often used in quilt block patterns and can scare the beginning quilter. BUT they don't need to.

In this post I will attempt to present to you, along with some other tips, different ways you can make a half-square triangle. Choose the method you like best and then you can make beautiful block squares that contain HST.

Before I begin, I should stress that I will talk about making a 1/4 inch seam. In reality, you should make a scant 1/4 - inch seam. If you take a full 1/4 - inch seam, when you press it open, it will be a little smaller than what you expected. That is why I like to even make the squares a little bigger than you will see in other instructions. (I talk about this below.) Then you can trim them up to be perfect.

I always followed directions and cut the squares the size instructed, but was then upset because after I sewed the squares together to make the block, my block would always be smaller than it was supposed to be. The worst time was when I was making a quilt for one of my granddaughters, I cut the sashing, sewed it together and then when I was going to sew it to the blocks, it sections were longer than my block. Did I mention stars would be formed at the corners. Well, I wasted all that time and material making the sashing. I have never made that mistake again. Now I don't even cut out sashing until I have the finished blocks made and trimmed to be consistent. Then I know exactly how long I need to cut the sashing pieces.

The first method I am going to share with you is the most recent method I have learned. It is called the TUBE METHOD. It works great if you are using "yardage" of fabric and not scraps. You can even use fat quarters if you are making smaller HST. (Recently I was helping my friend Fran make a quilt for her new grandbaby. She only had fat quarters and wanted to make a finished 8 - inch square, but the fat quarter wasn't wide enough to utilize this method with this big of a square.

For the "Tube" method, cut two strips the width of the fabric (wof) 1/2 inch wider than you want the finished HST to be. For example, for a finished 2 - inch HST, cut the strip 2-1/2 inches wide.

Sew them together with right sides facing 1/4 of an inch down each side (like you were making a tube.)

Mark your ruler with tape across the 3 inch marks - that would be a 1/2 inch bigger than the strip was cut or 1 inch bigger than the desired finished HST. (Another example - for a finished 3 inch HST, the strip would be cut 3-1/2 inches wide and the ruler would be marked at 4 inches.)

Match the raw edge of the seam with the edge of the tape. The point of the ruler should be at the seam on the other side.

With a rotary cutter, cut along edges of ruler.

Rotate the ruler around to the other edge. Line up the ruler with the cut edge. The point should be at the other side seam.
Cut along the other edge of the ruler. Then rotate the ruler back around and repeat process.

In my approximate 9 - inch strip I was using for this tutorial, I was able to get four "cut" triangles with only a little waste.

Press over the seams to set the stitches, and then press them open. The HST will measure a little bigger than 2-1/2 inches (which is good).
You want to be able to trim it down to a neat 2-1/2 inch HST. 
You will match the 45 degree line on the ruler with the diagonal seam and trim off the excess around the square.

Then rotate it around and match the 45 degree line again and the cut sides you trimmed with the 2-1/2 inch lines, trim the other two sides.

Here are my four perfectly cut 2-1/2 inch HST that will make a finished 2 - inch HST when sewed in a block.

and some fun designs I came up with using them.

Since I only had the four, you will have to use your imagination as to how the pattern would look with a bunch of them.

WHY I love this tube method....With just two seams, you can get a bunch of HSTs made. I also like that after they are cut, you have excess to cut away to make them perfectly. That's the secret to having HST work out so well in a block. If they all consistently measure the desired amount, then the seams will match up so that you have those "points".

The other two methods are the most common ones and are similar.

I have seen template patterns for triangles but I don't think I would ever just cut out triangles. It seems such a waste of time. Remember two right triangles will make a square or rectangle. So why not start with a square or rectangle and then with one cut, get two triangles.

What you have to remember is that you won't be using a 3 - inch square to cut two 3 - inch triangles to sew together to make a finished 3 - inch HST . The cut should be 3-7/8 - inches. BUT....

What I have found easier to do and remember is cut the square a whole inch bigger. (In my example 4 inches) Best thing about doing this is you have will a little excess to trim off to make that perfect 3 - inch HST. An inch is so much easier to remember than 7/8 and it is easier to measure by on the ruler. 

Both methods start this same way....Cut the square 1 inch bigger than what you want the finished HST to be. (Save some time and cut both of the prints at the same time....right sides facing.)  

Now is the difference....

Measure with a rotary cutter diagonally across the square. (Match one edge of the square with the 45 degree line on the ruler. The ruler should run through two of the corners of the square.)


Match the cut diagonal edge with the edge of your pressure foot and sew the two triangles together.
You can feed the next one through and not have to cut the thread until you are finished.

Press the seam to set the threads and then press the seam open.
The HST can be trimmed down to the
perfect 3-1/2 inch HST you are after to make a finished 3 - inch HST.
The other method using these two 4 - inch squares is to draw a diagonal line instead of cutting on it.

This time you will sew 1/4 inch from this line using the line as your match up with the attachment foot.

Once you finish, turn the square around and sew on the other side of the line.
Press the seam to set the stitches and
then cut along the line. You can do this with a rotary cutter or with scissors.

Press open and trim the excess to 3-1/2 inches to make the perfect 3 - inch HST when you sew them in a block.

My HST using these two methods....

Here is my favorite block which uses four HSTs for the corners. It is called a Churn Dash block.

This is the quilt I mentioned earlier that my friend Fran is making. Isn't it going to be beautiful!

So next time you see a pattern you like with half-square triangles, remember they are not so bad to do.

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