Before we jump into Quarter Square Triangles, a small disclosure: I was unexpectedly called out of town and of course I had planned on doing all my steps and photography on the day I had to leave. Of course!
(Personal note: my daughter gave birth to our second grandchild, and that necessitated a plane trip across the country!).
So....what to do? I worked up diagrams to accompany the information, in lieu of photographs. Full disclosure: I kinda like it. What do you think? It won't work with every post, but for some of these informational posts, I'm thinking I may use this format. Please weigh in on your thoughts about this. And just in case you were wondering what happened to those show stopping, award winning photographs (said with HEAVY sarcasm), now you know!
The Quarter Square Triangle (QST), sometimes called the Hourglass block, is made up of four (hence the “quarter”) triangle units. There are a variety of methods for making the QST unit, each with its positives and negatives. Let’s look at three different methods for making a symmetrical QST – meaning that all four quadrants or segments are equal in size and proportion.
Method One
Start with TWO different print or color fabric squares. Cut each square in half corner to corner TWICE to yield FOUR QST units from EACH square.
Combine TWO QSTs from Fabric 1 and TWO QSTs from Fabric 2. With right sides together (RST) and with a ¼” seam allowance, sew along one short side (as shown above) for each Fabric 1/Fabric 2 pair. Press.
Pressing Side Note:
General rule of thumb is to press to the darker fabric, or in the case of two fabrics of equal value, press to the same color fabric each time. In the example above you might press to the turquoise. I find that pressing seams open yields MUCH MORE accurate and flat blocks! I recommend sewing with 10 – 12 stitches per inch, and to press your seam open.
With RST, match up the center seams along the LONG edge and stitch with a ¼” seam allowance. Press. Repeat all above steps to yield a second QST block.
Stitching Side Note:
All stitched edges are exposed bias (that stretchy part of your fabric). Use care when stitching. DO NOT (I repeat – DO NOT) pull on your fabric as you are stitching as this will cause your fabric to stretch and your seams to curve, yielding a curved finished seam and a wonky block.
Pros:
- You can mix your prints and colors, or use scraps.
- It is easy to match your center seam, so chances of a perfect block are greater.
Cons:
- EVERY seam has an exposed bias edge, which can stretch and cause a wonky or wavy block.
Done? Nope – not quite yet. I’ll address the math AND the trimming at the end!
Method Two
Start with two different print or color fabric squares. With RST, match up raw edges.
On the wrong side of ONE square, draw a line corner to corner with a fabric friendly marking tool (pencil, chalk marker, water or heat soluble pen, air erasable pen).
Sew a ¼” seam on EACH side of the drawn line.
Cut on the drawn line. Press. (See Pressing Side Note above)
You now have TWO Half Square Triangles (HST). Rotate ONE HST 180 degrees.
Matching up raw edges AND the center seam, draw a line corner to corner ACROSS the pressed seam, as shown above.
Sew a ¼” seam on EACH side of the drawn line.
Cutting Side Note:
Before cutting your units apart along the drawn line, fold back the fabric and check to make sure the center points all match. We are going for a PERFECT hourglass look! If the points don’t match, take out your stitches, realign, and resew.
Cut on the drawn line. Press. You will have TWO identical QSTs.
Pros:
- The bias edges are stabilized, so you have a reduced chance of curved or stretched seams.
Cons:
- If you do NOT match up the seams COMPLETELY, from edge to edge, the resulting QST may be wonky. In other words, the seams, which should go corner to corner, may not!
- It is difficult to see if the center seam matches at the center of the block, so the center may not be a perfect match.
Method Three
Start with two different print or color fabric squares. With RST, match up raw edges. Yes, this STARTS like Method Two, but stick with me – there is a twist!
On the wrong side of ONE square, draw a line corner to corner with a fabric friendly marking tool (pencil, chalk marker, water or heat soluble pen, air erasable pen).
Sew a ¼” seam on EACH side of the drawn line.
Cut on the drawn line. Press. (See Pressing Side Note above)
You now have TWO Half Square Triangles (HST). Cut each HST in half corner to corner ACROSS the seam line. You now have FOUR QST units.
I’ve numbered the four units above (1, 2, 3, 4).
Pair a Unit 1 with a Unit 3, a Unit 2 with a Unit 4.
With RST, match up the long edge AND the center seam. Stitch with a ¼” seam allowance (careful, this is a bias edge). Press. You will have TWO identical QST blocks.
Pros:
- You can easily see the center seam, which makes it easy to match up the center seam and get a perfect block center.
Cons:
- The long edge is a bias edge. If you pull or tug while stitching, the seam may curve on you, resulting in a wonky block!
You may have thought to yourself, as you were looking at the diagrams and the unit shapes –“well, shucks, I can just use some HST units!”
Don’t do it!
Here’s why. If you DID use four HST units from two squares, cut in half corner to corner as I’ve shown above, when you place them together to make your QST, all of the outside edges are bias. This means they are easy to stretch out of shape.
Cons:
- The inside of your block may appear nice and straight but the OUTSIDE of your block may stretch out of shape and be wonky.
- It may be difficult to get an accurate seam when sewing to another block.
- If sewing two or more blocks together that have bias on the outside, it may be VERY difficult to maintain accurate block size and/or a straight seam.
The Math of QSTs
Because the quarter square triangle has TWO seams instead of one, you have to begin with a larger size square.
A good general rule of thumb is to add 7/8”. In patterns, if you see a measurement such as 4 7/8”, it is likely that is EXACTLY the size you need to use to get the unfinished size you need. Which means – no trim down room! Which means – you had better be channeling Mary Poppins while sewing. You know – practically perfect in every way!
Another approach is to use slightly larger squares to begin with that will provide you with trim down room. I can guess what you may be thinking. “But I don’t want to waste my fabric!”
I hear you! I squeeze as much as I can out of every inch as well. But let me ask you this. Is it really “wasting” fabric if you have a PERFECT block (or practically perfect) by allowing an extra 1/8” to ¼” for trimming? Uh hun – I didn’t think so!
Here is a chart of some beginning sizes, unfinished sizes, and finished sizes to get you started
For QSTs Finished Size |
Trim to Size |
Begin with (2) squares that are |
1” |
1 ½” |
2 ½” |
2” |
2 ½” |
3 ½” |
3” |
3 ½” |
4 ½’ |
4” |
4 ½” |
5 ½” |
5” |
5 ½” |
6 ½” |
6” |
6 ½” |
7 ½” |
7” |
7 ½” |
8 ½” |
8” |
8 ½” |
9 ½” |
9” |
9 ½” |
10 ½” |
10’ |
10 ½” |
11 ½” |
11” |
11 ½” |
12 ½” |
12” |
12 ½” |
13 ½’ |
Trimming QSTs
Personally, I think the best method is to make your quarter square triangle blocks slightly oversized and trim them down to the desired cut or unfinished size. For the purposes of trimming, we will use a 4” finished, 4 ½” unfinished/cut size QST.
Using a Square Rotary Ruler
Step One: Find your center point. Here is where you need to know your math – or how to use your calculator! For our 4 ½” block, the center point is 2 ¼”, or 2.25 – half of 4.5. 4.5 divided by 2 = 2.25. Easy!
Step Two: Place the diagonal line on your rotary square ruler exactly on one of the diagonal seam lines of your QST. Place the 2.25 mark exactly on the center point. Right handed folks will trim the right and top, left handed folks will trim the left and top.
Step Three: Rotate the block 180 degrees, so that the trimmed edges are now to the inside (or under the ruler) and the untrimmed edges are to the outside of the ruler. The trimmed edges should align with the unfinished size (4 ½” in our example) and the center of the block should be at the 2.25 mark. Trim the remaining two sides.
You now have a perfect QST!
Using a Tucker Trimmer
Trimming a QST or similar block is really where the Tucker Trimmer shines! No need to do the math!
The Tucker Trimmer not only has the standard 45 degree diagonal line from corner to corner, but it also has a second set of lines running from each measurement at the opposite angle, creating an “X”.
Step One: Place the Tucker Trimmer on top of the block to be trimmed, with the “X” for the correct size block lined up on the seams of the block, and the center of the “X” on the seam intersection.
Step Two: As with the square ruler, trim the right and top (right handed folks) or left and top (left handed folks).
Step Three: Rotate 180 degrees, with the trimmed edges along the desired cut size and the “X” on the seam lines and intersection. Trim the remaining two sides.
Again you have a perfect QST!
I recommend trying the different methods to find what suits YOU best. And practice! Practice WILL improve your skills!
Have fun stitching up QST blocks!
Deb Tucker, creator of the Tucker Trimmer tool (and many others) has a great video on using it. Find the video here!
These are my top three ways for creating Quarter Square Triangle units. If you found this helpful, I've created the post as a downloadable PDF tutorial. You can find it here. Kate is going to have more tips and tricks for making Quarter Square Triangle units as well, so hop on over to her blog to get more helpful suggestions!
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