I made this recently for the same thing. Make sure to use a heavy washer to make it easier to unscrew, but you thread the big hole saw on first stack a couple washers to make sure the smaller on has some backing and won’t bottom out on the thread then thread the existing hole size of hole saw onto the front of the arbor and use the existing size hole as your arbor. I’ll try to see if I can figure out how to resize the image.
