Half square triangles 8 at a time is the way to go if you need a lot of
them. It's easier than you think!
This tutorial will walk you through making eight half square triangles at once in two different ways.
If you are a precision cutter and sew your seams straight as an arrow use the first method. Some call this the Magic 8 Method.
However, if you are a beginner, use the second method which allows for a margin of error in cutting and stitching. This is the method that I use.
I like to make block units bigger than they need to be and then trim them to size. If things go wrong, then I have extra fabric which I can cut to size. Otherwise, if I don't have enough fabric to start with, I have to make the unit over again. Not fun. :-)
Using this formula allows for no waste - you only have to cut the dog ears off the (half square triangles) HSTs. In other words, no trimming to size.
But, your initial squares have to be exactly square and your seams need to be very straight. Otherwise, once cut your HSTs they won't be exactly the size you need. They will end up being a little smaller than you expected.
To get half square triangles 8 at a time with no waste, multiply the finished size of your HST by 2, then add 1 3/4 inches. Cut two squares to this measurement.
8 HSTs at a time = (finished HSTs size X 2) + 1 3/4 inches
Example: (finished 3 inch HSTs X 2 = 6) + 1 3/4 = 7 3/4 inches
If finished HST size is 2 inch, cut two 5 3/4 inch squares
If finished HST size is 3 inch, cut two 7 3/4 inch squares
If finished HST size is 4 inch, cut two 9 3/4 inch squares
If finished HST size is 5 inch, cut two 11 3/4 inch squares
If finished HST size is 6 inch, cut two 13 3/4 inch squares
If finished HST size is 7 inch, cut two 15 3/4 inch squares
If finished HST size is 8 inch, cut two 17 3/4 inch squares
Note: Use a rotating rotary cutting mat to make trimming easier.
Step 1 Cut one square from two contrasting fabrics.
(See photo below.) Place the two squares, right sides together, on top of one another. Using a pen or pencil, draw two diagonal lines, one from each corner to corner.
Step 2 (See photo above.) Pin the two squares together as shown (to prevent the fabrics from shifting as you sew the squares together). Stitch a 1/4 inch seam away from the lines on both sides of each drawn line.
Step 3 Cut the two stitched together squares into four smaller squares.
First, place a quilting ruler through the vertical center of the squares. Using a rotary cutter, make one vertical cut through the center of the squares.
Step 4 Keeping the pieces aligned and together, place a quilting ruler through the horizontal center of the squares. Make a second cut horizontally through the center of the units.
Step 5 Now cut the four squares into half square triangles along both diagonal lines.
Place a ruler diagonally from one corner to its opposite corner on the drawn line. Make a cut with the rotary cutter.
Step 6 Place the ruler diagonally from the other corners on the drawn line. Make a cut with the rotary cutter.
See your half square triangles 8 at a time... Cool huh?! :-)
Step 7 Open the half square triangles and press the seams towards the darker fabric.
Step 8 Trim the dog ears off the HSTs.
These 3 inch finished half square triangles 8 at a time are 3 1/2 inches unfinished. You can see that they came out to be that size, needing only the dog ears to be trimmed off.
Now for method 2.
Instead of adding 1 3/4 inches, add 2 or 2 1/4 inches. Then, once your HSTs have been cut trim them to size. Perfect compromise!
8 HSTs at a time = (finished HST size X 2) + 2 1/4 inches
Example: (finished 2 inch HST X 2 = 4) + 2 1/4 = 6 1/4 inches
If finished HST size is 2 inch, cut two 6 1/4 inch squares
Use one of these methods of making Half Square Triangles 8 At A Time for these quilt block tutorials on scrapish.com that use HSTs...