I have a small knob that I would like to radius an inside 90 union or junction. When I try to use radius/chamfer tool it wants to perform the function on the flat not portion creating the opposite of what I am trying to accomplish.
From what I can tell, the problem is that your knob consists of more than one body. The cylinder wall is a separate body from the bottom. Do a Union first, then the fillet radius should work (unless you prefer to have a chamfer).