Along with squares and rectangles, triangles are an essential component of quilt block design. Half-square triangle units, or HSTs, are squares made up of two right-angled triangles and they feature in many classic quilt blocks. There many different ways of creating HSTs and we will concentrate on a straightforward and failsafe method to make the Broken Dishes and Pinwheel blocks and you will find links to other HST techniques at the end of this post.
Quarter square triangles are the next step on from half square triangles and we will use these in the third block, Hour Glass. You can see the difference between HSTs and QSTs in the diagram below. For all the blocks you will need a quilt ruler with a 45-degree line.
Broken Dishes Quilt Block
Finished block size 12” square. This block is made up of four HST units, each constructed in the same way. Finished size does not include the seam allowance so the unfinished size is 12½” square. Seam allowance is ¼” throughout.
You will need
- One dark coloured fat quarter.
- Two differently coloured fat quarters to contrast with the light fabric – I am using a light grey and a mustard.
This method is based on cutting squares to make the HSTs. Each square needs to be 7/8” bigger than the finished HST unit required – the formula is:
Side of finished square + 7/8”
However, it is easier to round up to 1” and cut a little bigger. This gives us some wiggle room to trim each unit to an accurate size and a new formula!
Side of finished square + 1”
Background fabric: Cut two 7” squares. I am using a darker fabric for this.
Fat Quarters in two colours: Cut one 7” square from each of the fat quarters.
On the wrong side of each background square, draw a line along the diagonal, corner to corner using a soft pencil or fabric marker.
Pair each background square with a coloured square, right sides together and with the background square on top so the diagonal line is visible.
Sew a ¼” seam to one side of the diagonal line. It is more efficient to chain piece and sew this seam on each pair of squares continuously. Repeat on each pair of squares sewing a seam on the other side of the diagonal line. On each pair or squares there should now be a seam on both sides. Press flat.
Tip: If you don’t have a ¼” foot on your machine draw the seam lines in pencil either side of the original diagonal line.
Cut the unit in half along the drawn diagonal line using a quilt ruler and rotary cutter.
Each unit needs to be trimmed to 6½” square. There are two ways to do this.
Method one: Prepare the unit by pressing the seam either open, or to the side so it lies towards the darker fabric and open it up to make a square. With the HST unit right side up, place a quilt ruler on top so the 45-degree line on the ruler is aligned with the diagonal seam. Trim off the excess fabric to make a 6½” square. This also removes the extra ‘dog ears’ or excess seam ends.
Method two: With the unit unopened and in a triangle shape, you will need either a 6½” square ruler with a 45-degree diagonal line, or use a 6½” or larger square or rectangular ruler and mark a 45-degree diagonal line with masking tape or washi tape at the 6½” marks on each side edge. Align the diagonal line on the ruler with the seam stitching. Trim off the excess around the two ruler edges. The dog ears can be removed with scissors. Open out and press to make a 6½” square.
Arrange the units into two rows of two to make the block. Sew the top pair of squares together and then the second pair, pressing the seams to the darker fabric. Join the rows taking care to match the centre block points and press the final seam open. Your Broken Dishes block is complete!
Tip: Whether you press the seams open or to the sides on HST units is up to personal preference. There are advantages and disadvantages to both. Pressing seams open reduces bulk when units are joined and when the block is quilted but it is fiddly and time consuming and if your stitches are large it can strain the seam a little. Pressing seams to the sides, usually to the darker fabric, is quicker and makes seam point matching easier as the seams naturally nest together. It can also be bulky and lumpy and produce seam points that are hard to quilt.
Pinwheel Quilt Block
Finished block size 12” square. This block uses the same HST method as Broken Dishes.
You will need
Two fat quarters in contrasting colours.
Cut two 7” squares from each of the contrasting fabrics.
Pair the contrasting squares and follow steps above from the Broken Dishes instructions to make four HST units each measuring 6½” square.
Arrange the units into two rows of two to make the block. Join together using the same method as for Broken Dishes.
Your block is complete!
Hour Glass Block
Finished block size 12” square. This block is made of quarter square triangles. These are usually made in pairs like half square triangle units and the technique is very similar. The formula for cutting is:
Side of finished square + 1¼”
As before, it helps to add a little wiggle room so we will add 1½” giving us a formula of:
Side of finished square + 1½”
You will need
Two fat quarters in contrasting colours.
Cut two 7½” squares from each of the contrasting fabrics.
Follow steps 1-4 of Broken Dishes to make four HST units. Do not trim the units.
Press the seams to the side. On the wrong side of two units, draw a diagonal line running perpendicular to the diagonal seam so they cross at right angles at the centre. Place each of these units right sides together against the remaining two squares so that the seams are nesting; the light fabric will be against the dark fabric, the pencil line will be on top (see photo) and pin in place.
Sew two seams ¼” either side of the pencil line. Press and cut down the line with a rotary cutter and quilt ruler as you did with HSTs. You can now trim each quarter square unit to 6½” square as you did for Broken Dishes but this time keeping both diagonal seams aligned.
Arrange the quarter square triangle units into two rows of two rotating the unit each time. Join the block together as with the Broken Dishes block. Your block is complete!
Half Square Triangle Methods
- Easy HSTs using corner squares – this is a very simple and accurate method but it does use a lot of fabric and can be a little wasteful. Lori Holt demonstrates this here.
- Cutting squares in half and joining along the bias – this method is quick and efficient but a bias seam can easily stretch out of shape when sewn along and your squares can lose their shape and accuracy. This is the first method shown in this Connecting Threads tutorial.
- Camille Roskelley has a great tip using masking tape so you no longer need to pencil in a diagonal lines when sewing HSTs.
- It is possible to make four and even eight HST units using one step. You can see how at the Ludlow Quilt and Sew website.
Some quilter’s prefer to use a paper foundation to sew HSTs. This method uses a paper pattern that you lay over the fabric, stitch through and produces very accurate results. You can find free HST patterns to download and print in a variety of sizes here plus you can buy foundation paper here.
There are commercial versions of these patterns available too. Examples include ‘Half Square Triangles on a Roll’, ‘Quarter Square Triangles on a Roll’ ‘Thangles’ and Primitive Gatherings Triangle Paper.
Die Cutters like Sizzix and Accuquilt will cut half and quarter square triangles to a range of sizes – no trimming needed and ready to sew. They are a sizeable investment and do take up a bit of space!
Helpful tools to square up your triangle blocks and cut them to an exact size include the Bloc loc ruler which is size specific. It is hard to get hold of in the UK. There is also the Quilt in a Day Square up ruler which includes HSTs from 1” to 6½” on one ruler.
None of these are essential; they just make life easier, especially if you have a lot of triangle units to sew.
Next time we will move on to Flying Geese blocks and we’ll explore different construction methods as well as creating more basic blocks including a block that combines a range of square and triangle shapes. You can find me along with my sewing adventures, tips, quilt-alongs and tutorials at verykerryberry.blogspot.co.uk