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In Quilting/ Quilting Tutorials

How to Make Triangle in a Square Quilt Blocks

Have you ever wondered how to make a Triangle in a Square quilt block? This Tri-Rec quilt block tutorial will show you how to make these fun triangle quilt blocks using rulers to cut out your Triangle fabric pieces.

Check out this video tutorial to watch how I make the Triangle in a Square quilt blocks from start to finish:

What are Tri-Rec Quilt Blocks?

Tri-Rec quilt blocks are also known as Triangle in a Square quilt blocks. The top angle of the center Triangle shape is a little less than 60 degrees, which makes this triangle and Isosceles triangle.

Prep Your Quilting Fabric for Making Triangles

Before we begin cutting the Triangles, it is super helpful to prepare your fabric with spray starch or best press.

When piecing any triangles for a quilt, you’ll be sewing along the bias. The bias is a term used to refer to the diagonal of the fabric grain. If you grab a piece of fabric, you can pull it diagonally and see how much it stretches; it doesn’t stretch nearly as much if you pull straight on grain.

To accommodate for sewing on the bias, I find that prepping my fabric really helps to stabilize it and keep it from stretching while I am working with it. Watch the video linked above to see how I use Best Press to prepare my fabric. I do this for ANY project that will involve sewing on the bias.

Cutting out the Triangles

I prefer using Rulers like these to make Tri-Rec Quilt blocks. Alternatively, you can also use AccuQuilt if you prefer. Learn more about AccuQuilt here!

Wondering which rulers to use?

I should start off by mentioning that a Tri-Rec Triangle in a Square quilt block is NOT the same thing as an equilateral triangle or a 60 degree triangle. The center triangle shape is an isosceles triangle. Each of the angles at the bottom base of the triangle are the same, and the angle at the top point of the triangle is a little less than 60 degrees.

My favorite ruler for making Tri-Rec blocks is this one by Planted Seed Designs. Alternatively, Creative grids makes a larger size option that is also very nice! This one makes Tri-Recs up to 6.5″ and the Creative Grids set goes all the way up to 9.5″.

The rulers from Planted Seed Designs come as a set – it includes both the center triangle shape as well as the background shape too. The ones from Creative Grids are sold separately.

Cutting on Grain

Fabric Grain is particularly important when making Triangle in a Square quilt blocks. You’ll want the bottom edge of your triangle to be straight on grain, which means it wont be stretchy. Alternatively, this means that both sides of the center triangle will have some stretch in them, so be extra careful not to distort the edges while handling them.

If you are cutting out a lot of pieces for many Tri-Rec blocks, I like to begin by cutting WOF strips and then rotate the rulers to get the most shapes from the fabric without wasting.

You should note, if your background fabric is not a solid, you’ll want to be very careful to cut out the correct number of LEFT side triangles and RIGHT side triangles. The easiest way to do this is to cut them out with your fabric folded.

Tips for Piecing Triangle Quilt Blocks

When you’re ready to actually start sewing the fabric pieces together, you’ll want to be very careful not to stretch them, as the fabric is cut on a bias edge. Place them right sides together, leaving a little 1/4″ space at the top. Watch the video for the best explanation on how to line up your pieces.

For best results while piecing your quilt blocks, I recommend using a sharp new needle in your sewing machine. If you are using quilting cotton fabric, a size 75 or 80 needle is perfect. (A bigger needle will also work if that’s what you have on hand.)

If you find that your little triangle tips get sucked into your sewing machine while you sew – I have some tips to keep that from happening! My sewing machine tends to “eat” the corners and we definitely don’t want that happening!

First, use Leaders & enders – Leaders and enders are just bits of scrap fabric you can stitch on prior to sewign your actual pieces. They will keep the threads up and hold them in place before you feed your pieces into the machine. And an ender is the same thing just after you stitch your piece. The ender from one set can serve as a leader on the next if you don’t trim the thread. 😉

How to Piece the Triangle Quilt Block

Begin by lining up the center triangle with the right side triangle with right sides together. Have the tip of the side overlap 1/4″ for seam allowance, and stitch together. Press the seam open, and you’ll notice a little point at the top of the piece.

Once you’ve stitched one side of the background to your block, you can press the seam open with a hot iron and repeat for the other side. Watch the full video to see these steps in action!

Trimming Your Triangle in a Square Quilt Blocks

When making Triangle in a Square quilt blocks, I personally found no need to trim or square up the blocks after sewing. But of course, if you want to square them up, you can now use a square ruler to make each block the perfect size. I recommend that you pay close attention to the 1/4″ seam allowance at all 3 points of the triangle while you are trimming.

Putting Tri-Rec Blocks into a Quilt

The Triangle in a Square Quilt Block is a fun one for many different designs! You can play around with them yourself to create something fun, or check out my Bonanza quilt pattern which will be available in my shop soon! The Bonanza pattern includes 3 sizes and features Tri-Rec blocks! You can use this Triangle in a Square Ruler Set for the crib and throw size of the Bonanza pattern.

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