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Top 5 Tips on Trimming Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles
The Half-Square Triangle (HST) is one of the most commonly used shapes in quilting designs and has continued to make its way in the quilt world. From the very first quilts in history to modern-day designs. Half-Square Triangles consist of two right-angled triangles joined on the longest sides to form a square, hence the name.
 
When creating an HST, some patterns require you to trim (or square up) the unit. This process in quilt making can be mundane, and takes time and effort. However, this additional step makes a big difference in accuracy when it comes to sewing fabric pieces together to form your quilt block or top.
 
In this blog post I will be sharing my top five tips when it comes to trimming HSTs. And if you would like to work on your HST trimming skills, I have the perfect quilt pattern for you! It’s my Triangle Multiplier quilt pattern. It explores three quick ways in creating HSTs: the 2-in-1 (or 2-at-a-time) method, the 4-in-1 (or 4-at-a-time) method and 8-in-1 (or 8-at-a-time) method; and comes in two sizes: baby (37" x 43"/94cm x 110cm) and throw (55" x 64"/140cm x 163cm). You can download the pattern, discover different colourways and play around with the digital colouring pages here.
 
The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles Baby and throw size triangle multiplier quilt
 

Now, let’s get to trimming!

What You'll Need

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles required tools

The tools listed below assumes you have assembled all your HST units and you’re about to start to trim them:

  • Quilt pattern – in this tutorial I’m using HST units from my Triangle Multiplier quilt pattern. You can download the pattern from here.
  • Sewn half-square triangle units, not pressed yet
  • Iron
  • Wool pressing mat or ironing board
  • Fabric starch or flatter spray (optional)
  • Rotary cutter
  • Spare rotary cutter blades (optional)
  • Cutting mat – ideally a rotating cutting mat. Alternatively, you could use a small cutting mat.
  • Quilting ruler(s) with a 45-degree angle guideline – Depending on the required trimmed HST size, preferably a small square ruler and a medium size square ruler, i.e. 6½in x 6½in and 12½in x 12½in. If you had to choose one between the two sizes, go for the medium size ruler so it covers any dimensions up to 12½in x 12½in.
  • Non-slip quilting ruler grips (optional)

 

Top 5 Tips on Trimming Half-Square Triangles

Tip 1: Pressing Matters

Just like you would before you cut fabrics for you quilt project, be sure to press your HST unit with a dry, hot iron before any trimming commences. This is going to allow the HST unit to lay flat as you’re trimming and it will allow you to get a more accurate trim.

Another thing to note with ‘pressing’… it’s different to ‘ironing’. Ironing is a back-and-forth motion like you would with ironing a shirt. The vigorous motion of ironing can stretch and distort the seams and fabric pieces of a quilt block or unit, especially units like HST. This is because the seams are generally sewn on the fabric’s bias. To press, use an up and down motion with an iron to flatten your seams.

With pressing, it’s done in two steps:
1. Before you press the HST unit open or to the dark side, set the seams by holding a dry, hot iron on top of the stitches for a few seconds. This is going to help the stitches to sink into the fabric, reducing seam bulk.

 
The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

2. Open the HST unit and press the piece open or to the dark side for a few seconds. For a crisper and flatter seam, you could spray fabric starch or flatter spray. These sprays are totally optional.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Tip 2: Stay Sharp

A sharp rotary cutter blade is key for any cutting or trimming. This is going to allow you to get accurate, quick and clean cuts. You don’t want a dull blade to slow you down or create inaccurate piecing down the road. 

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Tip 3: Get a Grip

Things can slip and slide, especially when you don’t apply enough pressure on the ruler and pay attention while you’re cutting. And coming from experience, I have done that before and cut my finger by accident. If you are concerned about your ruler slipping and sliding as you’re trimming your HST units, you could get adhesive non-slip ruler grips. They’re these transparent sticky dots and they go on the back of the quilting ruler for additional traction.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Tip 4: Measure Twice, Cut Once

Take the time to familiarise and read over the instructions outlined in the quilt pattern or project. Make sure you have read Cutting the wrong size or number of pieces can stop a project in its tracks.  

Also check that you have the right quilting ruler size with a 45-degree angle guide to trim the HST unit. The 45-degree angle guide is going to allow you to match and ensure the diagonal seam that runs down the middle of the HST is centralised.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

And having the right size ruler for the require trimmed size is going to allow you to get more accurate and quick cuts. For example, you do not want to be using a 6½in square ruler to trim a 9½in square. The ruler is not long enough to make one clean cut.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

In this instance, you’d want to switch to a larger ruler, as shown below.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Tip 5: Do it in Batches

Throughout the quilting process you may find some steps quite repetitive, for example trimming (or squaring up) quilt units or blocks. To speed up things up, I like to do the same tasks in batches.

When it comes to batching tasks for trimming HST units, I like to:
1. Lay out a bunch of units in the same orientation on my rotating cutting mat. If you don’t have a rotating cutting mat, you could do the same thing on a small cutting mat.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

2. Place ruler on top of one HST unit. Match the 45-degree angle with the diagonal seam and check that the HST unit is within the required trim size as outlined in the quilt pattern.

3. Apply pressure on the ruler with non-dominant hand. With rotary cutter in your dominant hand, remove the top and right edges of the HST unit (top and left edges if you are left-handed).

Repeat with all HST units on the cutting mat.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

4. Without tampering with the HST units, carefully rotate the rotary cutting 180-degrees and repeat steps 2 and 3 until all HST units are trimmed.

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Laying out the units and cutting two edges of the HST units at a time in batches works to save time and effort from having to pick up, lay and cut one HST unit at a time. And this means, we can get to the fun sewing part faster!

The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles

Look at all this HST trimming confetti! Although trimming HST units take some time and effort, all that hard work pays off in the end because all your points, corners and blocks will match up nicely. And if you'd like to work on your HST trimming skills, I'd recommend that you try out my Triangle Multiplier quilt pattern.

 The Weekend Quilter x Fiskars Top 5 Tips on Trimming (squaring up) Half-Square Triangles Triangle Multiplier Quilt Pattern

This blog post is written by a Fiskars brand ambassador and sponsored by Fiskars. This post contains affiliate links, meaning, at no additional cost to you, if you use these links to buy something, I may receive a commission.