Half Square Triangles with No Trimming

There’s a phrase I hear over and over again with quilters, “I hate half square triangles!” When I ask why the answers are similar; “I hate trimming”, “they’re too much work”, “they’re never the right size.

My Take on Half Square Triangles (HST’s)

It’s all about accuracy, both in the cutting and in the sewing.

First of all, no matter how you cut them, if you’re not sewing your seam in the right place they won’t be right.

Start by Nailing that 1/4 inch seam!

Let’s do an experiment together. Take 2 strips of fabric that are 2 1/2 inches wide, and about 6 inches long. (Don’t sew yet.) Place them with right sides together and using an accurate ruler and a sharp pen or pencil, DRAW the 1/4 inch sewing line along one long edge of the fabrics and think about sewing them together.

Would you use a 1/4 inch piecing foot, or choose the 1/4 inch seam stitch on your computerized sewing machine? Or do you have a piece of painters’ tape stuck onto your throat-plate? Or a sticky note? Maybe a magnetic seam guide?

Here’s something to think about; if you sew directly on that 1/4 inch line, then press your seam allowance to one side, your block will be the width of the thread too small. It doesn’t sound like much, but it can be. That’s why we hear about a “scant quarter inch seam”..  In the garment industry there’s a term called “turn of cloth” which refers to the amount of fabric that gets “absorbed” into a fold or seam.

To make a block the right size, you need to sew right BESIDE the 1/4 inch line with no space between the line and your needle.

Go ahead and sew those strips together.

Press the seam allowance to one side and measure the finished width of your piece. It should be 4 1/2 inches. Exactly 4 1/2 inches.

Is it 4 1/2 inches? If it isn’t, pick out your seam and try again. Don’t even consider half square triangles until you get the seam exact.

My Presser Foot Choice

For 1/4 inch seams, including half square triangles, I use this foot. I sew on Husqvarna/Viking sewing machines and this is their foot. (part #412785545) Notice that it has no flange. In my years of sewing and quilting, I’ve seen many bent flanges. If you’re relying on that flange for accuracy, and it’s bent, well, you know. SOL. Notice that it’s not plastic? I’ve sewn through a few plastic feet, and when you do that, it leaves a burr on the bottom of the foot which drags on the fabric. (My machines have a setting so I can avoid sewing anything but a straight stitch, but I have to remember to set it, lol.)

Here’s where I direct the edge of my fabric for a perfect 1/4″ seam. Just to the left of the red line. See the arrow?

How I cut Half Square Triangles

I’m thrifty, with my time and my fabric. To me, cutting 2 squares, then drawing a line diagonally across them, then sewing 1/4 inch on both sides of the line before cutting along the line, then pressing open, then measuring and trimming, oh my, I’m tired just thinking about it.

Another method is to cut 2 larger squares and sewing around the outer edge before cutting twice on the diagonals before pressing, measuring and trimming. Tiring times four.

Maybe this method turns your crank, cut even larger squares, draw on both the diagonals, sew on either side, cut, press, measure and trim. 8 times more tired.

Ok, you need a special ruler. Here are two I’ve tested. Your local quilt shop likely carries one or the other, if not, I’ve added links to Amazon.ca. Both are designed to use strips pre-cut to the width of your desired half square triangle.

Easy Angle 4.5in

Fons & Porter Flying Geese Ruler

Cut two strips the width of your finished block. Place them right sides together and press them.

Square off one end, for me, the left end because I’m right handed.

Lay your ruler on the strip as shown. Exactly. See how on this ruler the yellow triangle extends beyond the top of the fabric? Also notice that the line for 2 1/2 is ON the fabric. Cut along the diagonal line. Lift the ruler, rotate it by 180 degrees and position it like this.

Cut along the straight edge for your next pair. Continue across the strip set, rotating the ruler and cutting. (Showing an Easy Angle Ruler and a 3 1/2 inch wide strip set this time)

It’s Time to Sew Those Half Square Triangles

Using a “scant” quarter inch seam, and beginning at the “blunt” end, string piece them. There’s no need to raise the presser foot, just take one stitch off one pair and shove the next pair under the foot. A new, sharp needle helps prevent “hungry machine”, I like to use a universal 80/12 for piecing.

As you cut them apart, trim the points off, as shown by my red arrows.

To open them out, press with the dark side up to set the stitches, then pull the top layer to open into a square and gently press. Not iron, press.

This post got much longer than I thought it would, but I just wanted to share more and more and more. I hope it helps you master half square triangles, remember, practice makes perfect.

Here’s a quilt I made that used 100’s of these, click here.