Here is the tutorial.
There is a part with variable radius.
Go to the surface tools and select offset surface.
select the variable radius and offset value is 0.
The surface that you just created you will mirror on the other side of the part.
Than go to insert, cut, cut with surface
Select the mirrored surface as a cutting tool. make sure that the direction of the cut is correct.
Than you have the variable radius on other side as well.
Than you can hide the surfaces or use the command delete body and delete both surfaces.