This quilt top was made by creating half-square triangle blocks with edges along the bias, forming these squares into pinwheels, turning the pinwheels on point so that the grain of the fabric is horizontal and vertical, and filling in the edges with half pinwheels (and the corners with quarter pinwheels).
Note: these directions are for creating a scrappy looking quilt. It could easily be made with pinwheels that are each made from two fabrics. Then the pinwheels would stand out on their own and be noticeable as pinwheels.
Step 1: Fabric selection
Choose 24 dark and 24 light six inch fabric squares. I had 24 deep red, magenta, reddish brown and multicolored six inch blocks on hand. I decided to use up some of my pale orange fabric for the light squares. The more different fabrics you have, the scrappier the quilt will be.
If you are making two-colored pinwheels, two of the fabrics that are set aside should match two of the 20 fabrics that are used in the next step.
Step 2: Create the pinwheel blocks.
In this step you can optionally align the fabric so that the patterns have a consistent orientation throughout the quilt. This is not really a crucial step, but in this example, one of the patterns had an obvious orientation that I wanted to preserve. The way I do this is by lining up the six inch squares so that they have the same direction relative to the fabric on the bolt. This direction is easily determined by stretching the fabric slightly. In the direction that the fabric is wound around the bolt, the fabric doesn't stretch at all. In the direction across the fabric, from selvedge to selvedge, it stretches slightly. So I made sure each square stretched from left to right and sewed them together that way.
For this quilt it is not actually necessary to use a 1/4 inch presser foot. However the same seam allowance must be used throughout, otherwise the quilt will be skewed.
Sew the squares together all around the side edges. I found it easiest to turn the corner with the needle raised on the sewing machine. Notice that the squares have the corners trimmed. This too is optional, but it will remove the points that occur when the resulting squares are pressed open.
If you are making uniform pinwheels with two colors each, these eight squares should match two of the squares that were set aside at the beginning.
Next sew the top and bottom halves of the pinwheels together. Press the seam loosely in any direction, or not at all. During the assembly of the top, these seams will lie in alternate directions, and it's not possible to predict at this step which way they will eventually go.
Step 3: Arrange the pinwheels and fill in the edges with squares and triangles.
Arrange the pinwheels on point in alternating rows of three and two. Take care to have them all point in the same direction. In this picture the pinwheels are rotated 1/8 turn clockwise so that the left top square is pointing up and the right top square is pointing to the right side. This means the seam joining the top and bottom of each pinwheel is on the downward diagonal. We are going to sew the rows together in this direction, so that we can orient the center seam of each pinwheel in either direction as necessary.
In the picture on the left, I placed the pinwheels from left to right without worrying how they looked together. In the second picture, I have rearranged them so that the different patterns of fabric are more evenly distributed throughout the quilt. This step is much easier if the original six inch squares are all different.
If you are creating uniform pinwheels with two colors each, assign the matching triangles to the side squares of the same colors. Fill in the side gaps with a third light and dark color, and fill in the corners with the remaining light and dark color.
Step 4: Assemble the top
We are going to sew diagonal rows of pinwheel blocks and then sew the rows together. With some care we can make sure that all the matching seams interlock as we join the edges. In order to do this as painlessly as possible, we will attach one block per row starting with the right side half pinwheel blocks, the lower right corner, and the lower half pinwheel blocks. Each of these will be attached to the adjacent block, and all the seams will be pressed in the same direction (in this case, to the right). These seams will eventually be matched with the seams created in the next step, which will all be pressed in the other direction.
The seam along the center of the whole pinwheel block must be adjusted to go in the opposite direction as the matching seam on the half pinwheel block. This may cause the seam on the whole pinwheel block to not lie flat.