Space Cadet Block 1: Half Square Triangle Tutorial

Welcome to the Space Cadet project! If you like to know what it is all about have a look here.

Let’s start with a classic, the Friendship Star block. It is a great beginner block. Consisting only of squares and half square triangle units it is easy to piece yet versatile.

You can use it as an all-over design, as part of a larger, more complex block, and it works wonderfully as a very special border design.

The following instructions are for a 6″ finished block, i.e. the block will measure 6.5″ with the seam allowances.

Instructions:

1. Cutting:

From your background fabric cut: 1 strip 10″ x 2.5″ and 1 strip 3″ x 6″.

From your star fabric cut: 1 strip 3″ x 6″ and one square 2.5″ x 2.5″.

Cut the 3″ x 6″ strips of both fabrics in half to get 3″ x 3″ squares.

Cut the 10″ strip of background fabric into 4 2.5″ x 2.5″ squares.

2. Sew half square triangle units:

Note: there are many ways to sew half square triangle units. This is the one I prefer. I always cut the squares that will become half square triangles a little larger than necessary and trim to the correct size later. It is always easier to trim down than to deal with units that are too small.

Draw a line on the backside of your 3″ lighter fabric squares. Put each marked square on top of a darker square with right sides facing.

Sew 1/4″ to the right of this line and then 1/4″ to the left of the marked line.

If you have this nifty [amazon-product text="Omnigrid Marking Ruler Trio" type="text"]B001CE38W0[/amazon-product], you can just mark your sewing lines in stead of the center diagonal. It’s a lot easier to sew on the line than to sew an exact 1/4″ to the right and left of the center line.

You should have 4 units like the one below. It is the dark side so you can see the seams better.

Press the square to set the seams. Make sure you don’t move the iron around on your squares to prevent distortions. Just set the iron down and let its weight do the work for you.

Cut the squares in half diagonally, on the line you marked earlier.

Now press the seams open with the seam allowance falling towards the darker fabric. This way the darker seam allowance won’t create shadows behind the light fabric and be visible from the front. Again, press without moving the iron around.

Trim the dog ears, i.e. the little triangles sticking out from your squares. On the picture below I have already trimmed 3 of the 4 half square triangle (hst) units.

Trim your HST units to 2.5″ x 2.5″ size. Make sure the diagonal line of your rules lines up with diagonal seam.

Lay out your HST units and 2.5″ solid squares.

Sew the units to make 3 rows. Press each row so that the seam allowances lie in opposite directions from one row to the next. This will make it much easier to match up your seams when joining the rows into the block.

I hope you can see how the little humps the seam allowances create butt against each other. This keeps them in just the right place.

Join the rows to finish your block.