I want to make a mini router table. The base material is a type of birch plywood with 15 layers or so, 21mm thick. Well if the dictionary serves me right, it's actually called "textured coated board" in English, (Siebdruckplatte in German), i.e. birch plywood with phenol resin coating or something like that - rough on one side, very smooth on the other.
Now, that aluminium plate has rounded corners. I first want to route out a rectangular region (with rounded corners) to only 8mm depth, to maybe a finger's width or two of the outer circumference of the alu plate towards its centre - leaving a rim for it to rest on at 8mm depth, making it flush with the upper plywood surface. And then completely cut out the inner rectangle, so the hand router can be mounted to the plate from the underside.
How do I do this to match the rounded corners of the aluminium plate perfectly? Do I need a straight router bit with exactly the same radius as the corner, or can this be done with smaller bits?
I guess it could be done with a guide bushing (correct English name for "Kopierhülse"?) and some sort of frame with rounded corners - which has to be larger than the alu plate by exactly the same amount... no idea of how to efficiently produce such a thing.
Side note for the worried: I did also buy a quality safety switch which ensures it will stay off after the end of a power outage. (and a momentarily-on foot switch, eh... to boot!)