Paul I agree with David about the zero flute cutters for the HDPE material. I also don't know why a 3/16" bit would not work for both the machining and making the holes in the axels. The toolpath you create to make the holes will stop the rotation to make the holes.
About the radii of 0.02 - 0.05 you would need a bit with a diameter of 0.04 - 0.10 of a radiused end mill with the correct radius desired.
I'm not sure where you are looking at the small radii so maybe we need a picture of the axel design you want to make.
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