From circle to octagon

Or how to turn dresden fan blocks into octagons.

I wanted octagons because it is easy to turn them into squares.
My dresden fan blocks have 24 wedges. I use a 15 degre fan ruler to make them.

An octagon has 8 sides so all I have to do is to turn 3 sides of the dresden block  into 1.
The first step is simple.

Step2  Rotate the block counter clockwise and cut the next 3 sides.

Step 3 (picture below).  Rotate again. This time keep the first side you created aligned with a vertical line of the cutting mat and be sure the new side you are cutting is aligned (parallel) with an horizontal line of the cutting mat. It is easier to place the block with the corners/points that have to be cut on the horizontal line of the cutting mat.
This step is important and you have to keep it in mind while you cut the other sides. It assures 90 degree angles to the final square blocks.

You can see below the vertical and horizontal sides aligned with the lines of the cutting mat.

Repeat until you cut all the sides.
Below is the finished octagon.  Love, love, how it looks and I did not waste too much from the original block.
The sides should be all equal in size. Not all of mine are but the differences are minor, I don't think I will have problems when joining the blocks. 
Now I have to add triangles in the four corners and I will have  a square.

What to do if the dresden block doesn't have a number of sides divisible with 8 (the number of sides of an octagon).
Example: 20 wedges dresden plate block.
Here is what you can do:

Fold the dresden block in half.  Mark the 2 half points onto the edges.
Fold in half again. Mark the 2 points onto the edges (you have now 4 points).
Fol one more time, you will have now 8 points marked onto your block.  Using the ruler, cut between 2 adiacent points.

Or , you can make a template. Use the same technique described above. Start with a circle and make the octagon. Place it on top of the dresden block in the position you want and cut around it.

I just found  here a calculator for different regular shapes, in case you need it.

I am busy now piecing 16 more dresden blocks for my quilt.
Happy Sewing!
Geta

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See also:
From octagon to square
Finished quilt