How to Make Half Square Triangles

In one of my challenge groups, there are a lot of new quilters, and I noticed that they are struggling with making the Half Square Triangles (HST) for Block 1 of the challenge.  So I thought I would do a blog post on it. 

There are many ways to make HSTs.  But if you are a new quilter, and don't have any special gadgets or rulers yet, then the easiest way to make them is to add 7/8" to your FINISHED size when you cut your fabric.  So if you want a 2.5" FINISHED HST, you would add 7/8" to 2.5" and you cut your fabric at 3-3/8".  Now that measurement gives you some wiggle room, because you will be trimming your finished square to the measurement you need.

Measure 3.5 Inches to cut your fabric

Most people would round that 3-3/8" up to 3.5" as that is easier to find on your ruler.
Once you have your fabric cut, turn the lighter fabric over and make a mark diagonally from one corner to the opposite corner.

 Now layer your light fabric on top of your dark fabric and take them to your sewing machine.  You are going to sew a scant 1/4" to BOTH sides of the line.  NOT ON THE LINE!!!  If you look at my pictures, the foot on my machine is NOT a 1/4" foot, so I am not guiding that drawn line right next to my foot.  It is a bit away from the edge of my foot, to give me the seam allowance I need.

Sewing the first scant 1/4" seam allowance

Sewing that second seam allowance

 Once you are done sewing both seam allowances, it's time to cut them apart.  As you can see in this first picture, the seam allowance is right on the 1/4" mark when I line up my ruler.  

Now, take your triangle to your pressing station, and gently press open your triangles.  You don't want to use too much pressure with your iron, because you are working with bias, and it is so easy to get it stretched, if you aren't careful.

When you are done pressing, take them back to your cutting station, and line up the 45 degree line on your ruler with the diagonal seam line and trim to the size you need your UNFINISHED unit to be.  In this example, I started with 3.5" squares of fabric, and I could get 3" HSTs.  But if your sewing isn't exact, and you didn't quite sew from corner to corner, you should still be able to get a 2.5" HST unit out of yours, if you started with 3.5" squares.  The important thing to remember here, is to line up the 45 degree line,  on your seam.  Make sure you have enough room on all 4 sides to get the size you need, before you trim.  If you look in this first picture, you can see the corner of my ruler is lined up on the corner of my square, and there is a dashed line that goes all the way to the opposite corner of the square.  That is my 45 Degree line on my ruler.  You don't need to worry about the other lines, the only one that is important for this exercise is the 45 degree line.

Trimmed to 3" square

 Now if you want to trim this down to 2.5 inches, you still need to make sure your 45 degree line is on your seam allowance, and then move the ruler so that the corner under the ruler is at the 2.5" mark.  Then you can trim two sides of your square with out moving the ruler.  Remember, we already trimmed all 4 sides to be straight.  So we can just move the ruler to our 2.5" mark and trim two sides to make a 2.5" HST unit.  Notice how the seam line is on the 45 degree line on the ruler... you need to make sure you do that, or your HST unit will not be correct.

Now your HST unit is ready to be stitched into your block.  I will write another blog post about sewing a HST unit to other units  to show what it will look like when sewn into a block.  You need to keep your 1/4" seams so you don't chop off your points.

Until next time.... Happy Crafting!!!