When I first started quilting, I thought HSTs (half-square-triangles) were these mystical, magical things that only the really good quilters knew how to use. You know, the REAL quilters. I made a couple of quilts with HSTs in them and I didn’t really understand them, so I viewed them as a necessary evil.
Recently, I did the Summer Sampler Series which was AWESOME for skill building and things kind of clicked into place. And now when I run into them in the Farmer’s Wife blocks, I’m honestly a little relieved that I can rotary cut and not use those templates!
HST math: The magic number for squares and rectangles is (finished size) + 1/2. So if you wanted a square with a finished size of 1 1/2″, you would cut a square 2″. The magic number for HSTs is (finished size) + 7/8″. So if you wanted a finished size of 1 1/2″, you would cut a square 2 3/8″. Theoretically. However. HSTs are tricky little things and having them be an extra 1/8″ is usually a good thing. You have to trim them anyway… and it’s easier to trim an extra 1/8″ off than to adjust or start over because you’ve ended up with it being a little too small. So I always add an inch to my finished size. So for finished size 1 1/2″, I would cut a square 2 1/2″.
There are 101 ways to do HSTs. Ok, maybe not, but there are a few. Here are two, and if neither one floats your boat, there are other ways just a Google-search away!
For both methods, you start the same way. I want my finished HST to be 1 1/2″, so I cut myself a 2 1/2″ square out of both fabrics. For the first method, you line up the squares together, facing each other. Draw a line from corner to corner.
Now sew 1/4″ out from the line on both sides.
Cut along the line.
Now you have two HST squares, ready to be ironed!
The other way, line up your square with the bias line on your cutting mat (or ruler).
Line your ruler up with the bias line.
Now do that with every single one of your squares. Then line up your triangles, one of each fabric with right sides together and sew a 1/4″ seam along the long edge.
Now you have your HST squares ready to iron. HSTs tend to run in packs, and if you iron the seams to the side, you can end up with REALLY bulky points. I iron my bias seams open.
And then if I’m sewing them together, I iron the seams to the sides just like with normal blocks.
But before you sew them together, they have to be trimmed. Have to? Well… Yes. Because you’re sewing them together on the bias, they’re going to be a bit wonky by the time they’re ironed. They’ll be more parallelograms than squares.
I use a small cutting mat to trim them on. My small cutting mat is 12″x12″ and it wasn’t very spendy. Totally worthy purchase. Plus, it marks the quarter and half inch lines, and that helps A LOT.
Line up your center seam with the bias line on your cutting mat. Since I want a 1.5″ finished size and this is now a square, I want it to be (finished size) + 1/2″, or 2″. I want all of the edges of my square to meet or overlap a 2″ square on my cutting mat.
Line up the ruler with one of the 2″ lines.
Now turn the cutting mat clockwise 90 degrees.
Line up your ruler and trim again. Keep doing it until you have your square at the right size.
This cut down (ahahaha) my cutting time tremendously. I find that sometimes I have to shift the square to line it up again, but it’s just a small shift and I’m ready to go. No repositioning the square, no contorting myself into funny positions to get it done. And then repeat for however many squares you need!