Hello,
Don't make an insert plate. Just make your router table top in one piece and use the router itself to make the circular opening. Screw the router directly to the top using CS machine screws into the tapped holes in the router base that holds the thin baseplate on, there are 3 of them. It is not difficult to make some insert rings to fit the routed hole you made in the router top. Make a template and route everything from this 'master'. You will need to get some sort of guide bush so you can rout with the correct offset to make a hole and matching inserts to fit, but that is not difficult and cheaper than buying router plates in the first place. If not, a square hole is easy to make inset 'rings' for if you don't want to buy a template bit and guide bush. Though these are useful for other jobs later. I have used my Triton router in a table like this for years. No router plate means no fussy levellers and less expense. I like the top to be one single piece, it is much nicer to use passing stock with no breaks in th top.
Mike.
