Pinwheel is just, well, a fun block. It looks like childhood, playgrounds, summer days....It's easy to do, using our old friend the Half Square Triangle.
I'm not sure that a 12" block is the best size for this particular block, but that's our standard size in this series, so I'll give that to you--as well as a 6" finished. (It's very easy to figure whichever size you want.)
For a 12" finished Pinwheel, you'll need:
(4) 6-1/2" HSTs (Half Square Triangles), light and dark (So, you'll start with 6-7/8" squares)
That's it, just 4 HSTs.
For a 6" finished Pinwheel, you'll need:
(4) 3-1/2" HSTs, light and dark (Start with 3-7/8" squares
Arrange the 4 HSTs so they "spin" in the middle. (To get the points to meet in the center, it's especially important that you do an accurate 1/4"--or, rather, scant 1/4" seam.) Also note that you can have them spin in two different directions, depending on how you "tip" the HSTs, so if you're making multiple Pinwheels, make sure you spin them all the same direction--unless you want them to spin in different directions.
Rows of Pinwheels make wonderful, playful borders, both inside and outside. They're perfectly splendid on baby and children's quilts. You can make quilts that are all Pinwheels, or alternate with plain blocks, or with other 4-patch blocks.
Can you find the 4-patches in this one? They just "fade into" the design!