I need to make a 1 3/8" wide dado for a mirror frame I am making. I know I can use my dado stack but would like to get a really flat true bottom. I have a dado clean out bit, aka pattern bit, I can use it in the router table to clean out the bottom of the dado. It only has 1/2" cutting diameter. Would it work and be safe to use it in the router table without the fence and make multiple passes to get the dado bottom flat. Hope I explained myself clearly.

Anyone ever do this?