Half-square triangles seem to appear in a lot of my quilts. That’s why I like to have several methods at my fingertips for making them accurately and quickly. The key when choosing a method is to look at the quilt pattern you want to make—if it’s scrappy, you might want to make only two HSTs at a time. If the blocks are repetitive, you might want to make either four HSTs at a time, or even or eight at a time.
To make a ton of similar HSTs at one time, I recommend using either triangle paper or the strip method. I haven’t written about these methods yet, but I probably will because they are useful methods to employ when you have a lot of similar HSTs to make for a quilt.
The most important thing to remember when choosing a method for making HSTs is to make your decision before you start cutting or even better before you buy any fabric for a quilt because different methods have different fabric and cutting requirements.
1. Figure out the size of the HSTs you need
For example, take a look at this block. It measures 12” finished (12.5” unfinished). The eight HSTs that make up the corner units are 2” finished (2.5” unfinished). They are all the same so I want to use the eight HSTs at a time method.
To figure out the size of the squares to cut, add 1 inch to the finished size of the HSTs in your block then multiply that by two. The HSTs in my block are 2” finished. Add 1” to that and you get 3”. Multiply that by 2 and you get 6”.
2. Cut two squares of fabric
To make eight 2” finished HSTs at a time for this block, I need to cut two 6" squares, one cream and one navy.
3. Draw a diagonal line from corner to corner on the back of the lightest square
After drawing the diagonal line, draw two sewing lines on either side of this diagonal line, 1/4-inch away. You don’t have to mark the sewing lines, but I always do. Marking the sewing lines makes it easier to be precise and when I’m making eight of something at one time, I wanna be precise.
A quarter-inch seam marker like the one shown here is a must-have for this technique--it really makes the process of marking those lines easier! In fact, with this tool, I can mark just the sewing lines and be done with it.
You can buy quarter-inch seam markers in several sizes, so I highly recommend purchasing a large and small one so you can use them regardless of how large the HSTs are in the quilt you’re making. The ones shown here are by Fons & Porter, and you can find them at Joannes, Amazon, and local quilt stores.
Notice also that I'm using my sandboard to keep the fabric square from wiggling while I mark it. You can read about sandboards here.
4. Draw a diagonal line from corner to corner in the other direction on the back of the lightest square
Draw a diagonal line and two sewing lines on the back of the lightest square going in the other direction. Again, you don’t have to mark the sewing lines, but I highly recommend it.
5. Place the squares right sides together, pin, and sew
Pin away from the sewing lines.
Sew on all four sewing lines. If you didn’t mark the sewing lines, sew 1/4” on either side of the diagonal lines.
6. Press the square
Pressing the square to set the seams and to flatten everything nice and neat before you cut these HSTs apart.
7. Draw a line across the square through the middle in both directions
Draw a vertical line down across the middle of the square. Draw another line, this time horizontally across the middle of the square. These two lines will help you cut your HSTs apart accurately.
Notice that I’m using my handy-dandy sandboard to prevent my square from wiggling while I mark the horizontal and vertical lines.
8. Cut the HSTs apart on the cutting lines
Cut on the vertical and horizontal lines you just marked in Step 7.
9. Cut the HSTs apart
Cut each of the HSTs apart. If you marked the square on the diagonal, cut on this line. If you used a quarter-inch seam marker like I usually do, you may have marked only the sewing lines and not the diagonal. That’s okay because you don’t have to cut exactly in the middle—just between the two sewing lines.
10. Trim the HSTs to their unfinished size
The HSTs in our block are 2” finished, 2.5” unfinished. So you must trim your HSTs to 2.5 inches. I have a shortcut that I use to trim HSTs that is superfast and that’s what I’m going to show you now. For this shortcut to work, you’ll need a small square ruler and either some ruler tape or a dry erase marker. You can also use the Quilt in a Day Square Up Ruler to trim your HSTs.
If you don’t own the Quilt in a Day ruler or you don’t want to mark your square ruler, you can trim your HSTs the conventional way—after pressing. Jump over here if you prefer to trim your HSTs after pressing.
Still here? OK, here goes. Again, your HSTs are not pressed yet. Mark a line on your square ruler connecting the marks on the ruler that match your HSTs unfinished size. I want to trim my HSTs to 2-1/2”, so I’ve marked a diagonal line connecting the 2-1/2” mark on two sides of the square ruler. You can mark this line with ruler tape or with a dry erase marker.
You can easily skip this marking business by buying the Quilt in a Day Square Up ruler, which is designed for trimming HSTs. Since I make so many HSTs, you can guess which way I typically go.
Lay the mark you’ve made on the SEAM of your HST triangles and trim. Trim both sides of the HST.
Because trimming both sides means you might have to rotary cut horizontally (which is not safe because the rotary cutter might slip and cut you), I recommend placing the HST on a turntable cutting mat or using a safety glove on your non-cutting hand. Fons and Porter sell a glove they call the Klutz glove that’s perfect for this. And no, I don’t work for Fons and Porter. I just love some of their products and the fact that you can get them at your local Joanne’s and on Amazon.
You can save yourself even more time by carefully aligning the top edge of the ruler with the top edge of the HST and placing the diagonal line on the seam. At that point you only have to trim only one side and call it done, done, done!
11. Press the HSTs
Press open or to the dark. Pressing open may help the block to lay flatter--especially if a lot of seams are coming together at the intersections like they do in a pinwheel block.
You’ll notice that after pressing, two dog ears appear on either side of the HST. You can avoid this by cutting off the dog ears prior to pressing.
You now have eight matching half-square triangles, ready for piecing into your block.
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