A lot of designs for this type of tool are on the net and I thought this one was good and easy to build.
The main rotor has a large diameter step of about .250 deep. The base has a recess for this step. I made them fit as close as I could and then did a bit of polishing for a smooth rotation. The flat head hex screw in the bottom is all that holds the rotor on the base. The recess was greased and then assembled with grease and one screw. The screw is set with blue locktite to a snug position. Feels quite smooth in rotation and very snug for good turning. If it ever develops chatter I can always tighten the screw a bit. So far I have only used it once! The part I made is the radiused knob on this tool!