Sunday, November 28, 2010

Half Square Triangle Tutorial

This little tutorial is for other ladies not using the EZ Angle ruler for making half Square Triangles in Step 2 of Bonnie's Roll Roll Cotton Boll Mystery.

Bonnie wants the units to finish at 3" - this means they'll measure 3" in the finished block so they will need to be 3.5" raw edge to raw edge.

Bonnie made hers in sets of 4 so I speed pieced mine in 4s using the standard formula for making HSTs.  This meant cutting rectangles measuring 3 7/8" x 7 3/4" and a very scant seam allowance.

BUT I feel the seam allowance is a little too scant so I suggest you cut your rectangles 4" x 8"

Next mark your rectangles on the wrong side of your fabric as I've done below - at the 4" mark and then lines extending to the top diagonals.  These will be your CUTTING lines.

Next, pair your pink and brown (or whatever colours you're using) rectangles, right sides together and sew a scant 1/4" seam along either side of the diagonal lines as shown below.

Cut along the ruled lines and you get 4 HSTs

The HSTs should measure 3.5" raw edge to raw edge.  If they're a little large, trim them down slightly.  They should not be too small.  If they are then your seam allowance is too big.

Please email me through my profile or leave a comment if you have any problems.


  1. I love making my 1/2 square triangles this way. Thanks for posting.

  2. Yup, made mine this way too, although I did cut my rectangles into squares before sewing - made chain piecing a total breeze.

  3. I have the EZ angle but still used this method for mine too.

  4. How to make sure that you're sewing 1/4" on either side of the cutting line? My 1/4" foot has a "lip" or "edge" that's designed to run along the edge of the fabric that I'm piecing together ... when I keep that lip or edge against the fabric, I know I'm getting a 1/4" seam. That won't help me make my HST's using your method. I've made a goodly number of quilts, but I've never made a quilt using blocks that require triangles because I've been too afraid of triangles (getting them to the right size, fear of lopping off points, etc.) ... I like your method because it allows me to trim if necessary (you can always cut away but you can't add ha!). Any advice? ;-)

  5. I hope you don't mind but I'm going to post to the group that sentence in here about finished size of the said it clearer than I've ever seen it.

  6. I don't mind at all - thanks for doing that Cheri!

  7. nice tute!!! looks like everything is coming along nicely!