How to easily cut quilt squares on the diagonal

Hi friends!

Today I wanted to do a quick post on how to easily cut quilt squares on the diagonal!

Cut Quilt Squares on the Diagonal

Have you ever tried to cut a square in half on the diagonal and had a hard time lining up the ruler? You get it to line up with the bottom but by the time you adjust the ruler at the top of the block, the bottom is no longer lined up. Arg!

Here is my tip:

First, turn the square on point and line up the ruler with the bottom point of the square. Make sure you can see the point, don’t cover it.

Second, open your rotary cutter and place the blade right at the tip, up against the ruler. NOW, you can move the top of the ruler to line up with the top point of the square and the ruler and rotary cutter will hold the bottom in alignment!

Once you have top lined up, then you are ready to cut! And since you have your rotary cutter ready to go, you don’t have to worry that things will shift while you go grab the cutter. Ta-done!

The 2 triangles are called half square triangles.

Which one can get confused with Half Square Triangle Units.

Half Square Triangle (HST) units are units made up of 2 half square triangles sewn together. But since we all usually make them using the 2 at once, or maybe the 8 at once method, we never actually cut the triangles! We sew first and cut later.

Want to know more about HST units? Click here.

Cut Quilt Squares in half on the diagonal – Twice

When you need to cut a square into quarter square triangles, you need to cut on the diagonal twice.

Make your first cut the same as for the half square triangles.

Then, without moving the triangles, line the ruler up along the other diagonal and make your second cut. If you have a rotating cutting mat, this makes it easy.

You will have 4 triangles called quarter square triangles.

What’s the difference between quarter square triangles and Quarter Square Triangle (QST) units? A QST unit is made up of 4 quarter square triangles!

Want to know more about QST units? Click here.

Tips on working with Bias

When you cut a square in half (or in quarters) you end up with bias edges being exposed. Those edges are stretchy which is why bias strips are sometimes used to create binding for a curved quilt, or in appliqué when you need a flower stem to curve.

When you cut a square in half on the diagonal once, the long edges of the triangles are on the bias. Be careful with those edges, handle gently and try not to pull on them or stretch them.

When you cut a square in half on the diagonal twice, the short edges of the triangles are on the bias.

If you are worried about stretching them, you can spray starch on your square before cutting to provide some protection.

When would you need to use half square triangles or quarter square triangles? There are some more complex units in quilting where you need them because you are not making a HST unit or a QST unit; you are adding a triangle to the side of another unit. As a matter of fact, for one of the blocks next week in the Sisterhood quilt along, one of the units uses both of them!

Hope that helps!

happy quilting!

Kate