: Place your new router plate on the table, where you want it. Butt
: pieces of MDF against all sides and clamp down. Remove the router
: plate from the table. Get a flush trim bit and router you opening.
That'll make a hole exactly the size of the router plate, won't it?
Making it fall right through.
What you'd need instead is two bits. One with a bearing near the shaft,
where the bearing is larger than the diameter of the cutting portion by
some amount, say 1". Rout a hole through the table with that.
Then use a rabbeting bit with a cutter the same amount bigger in diameter
that its bearing; use this to rout a rabbet around the hole,
at a depth equal to the thickness of the routr plate.
Then hope the corners fit.
-- Andy Barss