Transfer screws are the easiest way to get the exact hole locations. Remove your sub base plate, put it and the screws in a zip lock bag then label it. Install the transfer screws an even number of turns into the router base. In photo 3 both the large Porter Cable 3 hole mounting pattern and the smaller Bosch 4 hole mounting pattern have transfer screws in them.
If you are installing a mounting plate or base that accepts Porter Cable guide bushings you can use a centering kit like the ones shown from Rousseau or Infinity. The Rousseau kit includes the centering ring, pin, transfer screws and longer mounting screws. A centering cone will work for these and other sized openings; I recommend the Bosch centering cone as it has a much larger diameter than the DeWalt centering cone which only works in the PC sized openings.
Center your router using either the centering kit or cone and lightly tap the base with a hammer. This will mark your hole locations in your material.
Since you are asking about the DeWalt 625 I thought you might be interested in seeing the Woodrat plunge bar. With this bar installed you can plunge your router with one hand. Woodrat also offers plunge bars to fit other routers.
"Living in the D" (this means Detroit!)
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Last edited by Mike; 06-03-2016 at 12:40 AM.