Tuesday’s Triangle — Half Square Triangles with a Ruler

16 08 2011

Once again this week, I’m showing another way to make half square triangles.  This time I’m using a ruler made specifically for this purpose.

Start by cutting two strips of fabric 1/2 inch larger than the desired finished size of the block.  I chose to cut two strips right side together at one time.  That way the triangles are ready to stitch as soon as they are cut.  Cut off the selvedges on one end so there is a clean straight edge. 


Omnigrid makes the triangle rulers that I use the most.  They come in two sizes, one will make up to a 6 inch finished block and the other up to an 8 inch finished block.  If you are searching for them their names are R96 and R96L respectively. (There is also a metric version called the R915)

A close-up of a portion of the ruler shows a circle and arrows which show the proper direction of the fabric grain line when cutting half square triangles.  The numbers on the lines refer to the finished size of the half square triangle not the cut width of the strip.  There are also a lines across the 45 degree angle tips.  This line is to be lined up with one side of the strip.

There are other manufacturers of rulers that follow the same concept.  I have one from  EZ Quilting called Easy Angle. (Have I mentioned I’m the Queen of Gadgets?  The right tool for the job and all that.)  The main difference on that ruler is the numbers refer to the cut size of the strip rather than the finished size.

 Fons & Porter also have a ruler that will do the same thing it is called Half and Quarter, it makes both half square triangles and quarter square triangles.  (Omnigrid has a separate ruler for quarter square triangles.)

To cut triangles, line up one straight edge of the ruler with the clean-cut end of the strip and line up the appropriately numbered line with the long cut edge of the fabric strip.  The line at the tip of the ruler should line up with the other long cut edge.  For my example, I’m making a 2 inch finished half square triangle.   With the Omnigrid ruler I line up the line labeled 2 and with the Easy Angle I would line up the 2-1/2.  Cut along the angled edge of the ruler.


Flip the ruler over and line up the angled edge with the last angled cut, again lining up the appropriately numbered line and tip. Cut along the straight edge.


Continue cutting until you have the necessary number of triangle units or have finished the strip.  With right sides together, line up the long angled edge (the only bias edge) with the edge of a quarter-inch presser foot and stitch.  Chain multiple triangle units together.

Press the triangle units flat to set the stitches.

Press the seam toward the darker fabric.

And ta-dah — a finished half square triangle!

This is my favorite method for making half square triangles.  Probably because there is no fussing with marking, or cutting after stitching.  It’s just cut, sew, press DONE!  That doesn’t mean it is the best method for every application.  It works great when making blocks that have squares as well as half square triangles — i.e. a nine patch — because one size strip makes both the squares and the half square triangles.




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