homebrew main shaft

there are various designs for the 10 ft homebrew turbines ,mostly very similar. All have a 1 inch or bigger mainshaft riding on bearings.
I was reading about the turbine from Wisconson that was posted a few weeks ago by the builder. He tries to show how the keyways on the shaft hold the rotors in place. But it wasnt clear and I couldnt really get it. How do you fasten the rotor hole on to those keyways in such a way to never mover or wobble??? It doesnt seem that a set screw would hold and if so how does the screw attach to the rotor?? I am thinking of doing a 10 ft Otherpower style turbine...