Getting a Perfect Pinwheel

How to make perfectly flat pinwheel blocksLast week I showed you how to make Half Square Triangles (HST) fast, using the Magic 8 Method. Today, we’ll add to that with a full tutorial on how to get pinwheel blocks that are nice and flat. It’s important to get your pinwheel seams as flat as possible so that when quilting you don’t run into bulky seams that could distort the quilting, break the thread, or even damage the needle. Longarmers are probably jumping for joy upon reading this post! So, go ahead, impress your longarmer with your fancy pinwheel seams…

Let’s get started!

Getting Matching Points on Pinwheel Blocks

Alright, so you’ve got your Half Square Triangles sewn, pressed, and trimmed—no problem! Now it’s time to create your pinwheel blocks.

First, lay out four Half Square Triangles (HST) to form pinwheels, as shown below. Make sure that your triangles are pointing in the correct direction.

how to make a flat pinwheel

Sew together two top and two bottom HSTs. If you followed my Magic 8 tutorial, you’ll already have your seams pressed away from the background fabric. This will allow you to butt the two diagonal seams right up against each other. Then you’ll have perfectly matched blocks.

how to match seams on half square triangles

Reducing Bulk in Pinwheel Seams

To make sure that your pinwheel seams aren’t too bulky, try this trick! When sewing your two 3″ blocks together (as shown above), leave the top 1/4″ of the set unsewn. In other words, start sewing after the 1/4″ seam as shown at the top right of the image below. You’ll see why in the next step! Press seams towards the background fabric, just like you did before.

how to sew fast half square trianglesReducing bulk in pinwheel seams

Now, join both halves together along the long edge, butting those seams right up against each other, as before.

 how to reduce bulky seams in pinwheel blocks

Pressing for a Flat Pinwheel Block

Here’s the important part: Gently press the center of your pinwheel seam to open the seam up. This will push one side up and one side down.

the flattet way to press a pinwheel

Once you’ve got it how you want it, press. Press it really well! You’ll know you’re doing it right when you see a mini-pinwheel in the seam allowance, just like the image below.

How to press a pinwheel block flat. How to reduce bulk in pinwheel seams.

Isn’t that super cool?! I’m sort of a geek about how the back of my quilt looks, and this really gets me going! Look at that teeny tiny pinwheel AND the seams are all going the same direction (#love). Not only is it cool and organized, but this is the best way to get a flat quilt top when sewing pinwheels. And it really does make a big difference in the end result—there’s nothing quite like a nice, flat quilt top.

What a Pinwheel block should look like on the back

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Make sure to Pin this post for your next pinwheel quilt!

An awesome guide on how to sew and press pinwheel quilt blocks so that they lay flat. Reducing bulk in pinwheel seams is totally worth the effort!




  1. Wow! That’s impressive! I’m going to try it the next time I’m sewing a pinwheel!

  2. This is so cool!! I love making pinwheel!! Any pinwheel!! I never noticed the mini pinwheel on the back!! Thanks so much!! I have passed this on to my quilting friends!!

  3. Well, blow me down! Pity goodness, as Aunt Peggy would say; why didn’t I think of that!!!! What a clever idea! Thanks!

  4. Have done half squares before without giving much thought to details. Thank you for directing me to more careful ways! You set great standards. Thank you again.

  5. Excellent. I really appreciate the close up photos of the demonstration. I am going to sign up for your blog. Thank you.

  6. Thank you Rachel for this very timely post! I was joining flying geese into a square and that last seam always causes a dilemma. Which way should I press it, or should I press it open? What about that huge bump in the centre? With this method, the center is flat and all the seams go the way they should! Excellent! I’ll be sharing a link to this post to all my quilting friends.

  7. Thanks for sharing that tip. I made a kaleidoscope quilt which had 8 pieces of fabric coming together in the centre. Maaan…I tried everything to get those suckers flat! Its the lumpiest quilt I’ve done yet…I wonder if your trick might have helped?
    Next time I will try it.

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