I designed this Router Corner Radius Tools in Fusion 360. They are based on existing ideas in woodworking but I wanted to design something that would be easier to 3D print and making these one sided makes it easier to 3D print. Check out my picture of how I setup my supports since the back is not needed as a reference surface. I designed these in both Metric and Imperials sizes. 1/4", 3/8", 1/2", 5/8", 3/4 and 6mm, 9mm, 12mm, 16mm, 19mm.

I hope you enjoy and please post pictures of your printings.