This 3D pinwheel looks really complicated, but it’s actually easier and faster to make than a traditional flat pinwheel.  I made this pinwheel for a fabric manipulation element of a fidget quilt block.

All you need is four squares of your background fabric and four squares of your pinwheel fabric.

What size should my squares be?

For a 10″ block (10.5″ unfinished), your starting squares should be 5.5″.
For an 8″ block (8.5″ unfinished), your starting squares should be 4.5″.

For different size blocks, you’ll need a different size of starting squares.  If you have Excel or another spreadsheet program, you can use download this calculator tool I made to help you quickly get the proper size squares for your block.

3D Pinwheel Block Size Calculator

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3D Pinwheel Block Size Calculator

Instructions

1. Place your four background fabrics face up on a flat surface.
2. Take your four pinwheel squares and fold them in half diagonally, right sides out.
3. Place your triangles on top of your background fabric, then take  one of the points and fold it into the corner of the triangle as pictured below.  Pin in place:
   
4. Sew the folded triangles into place approximately 1/8″ from the edge of the fabric.
5. Repeat for all four, taking care that you are sewing each folded triangle the same direction as each other.  You’ll end up with four identical folded units that can be arranged like so:
   
6. Take two of your units and sew them together using a 1/4″ seam allowance.  Your previous stitches will be caught within the seam so it won’t show.  Be careful when sewing because at the folded areas, you will have a lot of bulk.
   
7. Repeat for your other row.  You’ll end up with two pairs like this:
   
8. You’ll want to carefully iron your seams, either opening them up to make them flat, or pressing to one side.  I prefer to press to the side, so I pressed my top row in one direction and the other row the opposite. This allows you to nest the seam to help flatten it.  As you can see in the top photo below, the seams are facing opposite directions.  Butt the seams as close together as possible then pin in place.  Sew!
   
9. After sewing, press one more time and enjoy your new 3D pinwheel block!