Tutorial - How I Make HSTs (Half Square Triangles)

I know when I am working on a technique I love to go out into blog world and see what others do.  I tend to either find a technique that appeals to me, or use a combination.  With that in mind I thought others may find this helpful.

HSTs are a bit of a mainstay in quilting.  They are a very strong geometric design element with a limitless possibility for patterns large and small.  You find them in hundreds of traditional quilt blocks and border treatments.  They are also a fabulous addition to any free form design as they tend to draw the eye.  Many quilt designs use HSTs to draw the eye across the quilt.

Since HSTs are so prevalent there are many patterns that call for hundreds and sometimes a thousand or more.  Make that many HSTs can be very tedious and problematic.  Working with the diagonal weave opens up a lot of stretch while sewing and possibility for measuring mistakes and frustrated quilters.  It's also really frustrating to make them one at a time when you may need 20, or 100, or 1000.  I am always looking at ways to make things easier and a bit faster while maintaining or increasing accuracy.  This method is the one that works best for me.

Tools -
Rotary cutter and mat
Sewing machine
2 or more fabrics
Ball point pen
Clear rulers for marking fabric
Optional - 2.5" quare clear ruler with 45 degree mark through the center

To start I usually decide how many HSTs I want to make.  I tend to make extra just incase I made a mistake at any step - design to cutting to sewing.  That way I have substitutes if needed.  For a guild challenge the design I made calls for 244 HSTs, so I elected to make 250+.

Next step is to decide on the size of your HSTs.  I recommend for the square up step you have a square ruler the same size as your HST, but it is not needed - just really nice.  For this project I am making 2.5" HSTs for a finished 2" size.  The mathematical rule for HSTs is to use a square 7/8" larger than your finished size for precise HSTs.  However, I prefer to square mine after sewing them, so I go up to the next inch.  In this case I am using a 3" square base.

I am using a selection of orange and yellow fabrics for my light fabric with a black fabric for the 2nd fabric.  I will draw my line guides on the wrong side of the light colored fabrics.  To start I cut 9" square blocks and equal number of front and back.  The 9" size was arbitrary - I wanted a size that is easily handled under the needle but did not wish to cut a lot of squares with a smaller size.

Next I use my pen on the wrong size of the yellow fabrics and draw out a 3 X 3 grid, basically outlining my squares for the HSTs.  These will be cutting lines so I am not worried about the ink running or showing on the front of the quilt - all of the ink will be cut away or under the seams.

After the straight lines I then draw out my diagonal.  These are going to be both guides for sewing and cutting lines.  I am only drawing a diagonal once through each square.  I also chose a pattern that will make a continuous sewing line in a square shape twice, than a second line on the long diagonal back and forth.

Once I have all the lines drawn I pin my 2 fabrics for the HSTs right side together, and then using my 1/4" sewing foot on my sewing machine I sew a scant quarter inch from all the diagonal lines.  Here I have shown the finished lines on both the front and back of the blocks so you can see.

Next, I start cutting.  If you are very careful and precise you can cut these in stacks with a rotary cutter.  You can also use scissors if you prefer.  I cut the straight lines first, then the diagonals.

Here is where I differ from some people.  I square up my HST before I iron it open.  Using my little square ruler I set it so the 45 degree line is a thread above my sewn line.  I then cut off both the excess edges and the tags along the sides.

 This leaves me with a very precise HST ready to iron open and use in my project!

The cool thing about this method is its great for mass production and can be modified to fit the fabric sizes you have.  I had one piece that would not make the full 9" square so I made it 6" x 9".  Just remember your cutting lines and your sewing lines - you only diagonally sew thru each block once.

Once I got my HSTs made I could start putting together my guild challenge. Here is the start!


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