This will take a little bit of mechanical work to complete. All parts printed without supports. Parts and tools I used.
First getting the rod end diameter down to size. I used a hand drill and a 1" tabletop belt sander. I chucked the rod up and started the drill slowly and eased the rod to the belt to turn the end diameter down to about .275 to .300 by ¼ back (7 to 7.5mm x 6mm). I used the other hand to support the rod. Hard part: Once done center punch the end of the rod as close to center diameter as possible. Drill 7/64 down center of rod about ½ inch or more. Stressful part: Tap 6-32 far enough for screw with washer to up on end. Could get by with a ¼ inch long screw. If you are fortunate to have a metal lathe this task will be a lot easier.
Assembly: Super glue threaded rod tightly into knob. Add pivot block onto thread. Use 5/16 washer on turned down diameter. Add clamp plate. Use small washer and screw and tighten.
2/8/2023 Added new piece that could help. Threaded drill guide. Screw this onto the end of the 3/8-16 threaded rod for a 7/64 tap drill for the 6-32 screw or ream it out first a little larger for a tap drill size for a 4mm screw.
3/9/2023 Modified pivot block to be stationary. I noticed the original seemed to be a little troublesome when using it. I made the diameter a little larger for a better fit. Added a bar in front to make it stationary. Rounded over the top. Listed as V2.
The author marked this model as their own original creation.