I went through the same thing a few months ago. The answer is straightforward, but not obvious. I recommend first cutting the center hole (clear through) and then adding the recessed lip for the plate to rest on. A plunge router, hand held, is best for this process. This is far simpler if you are lucky enough to have a router that takes 1-1/2" guides but since more have 1-3/16" guides, my instructions will assume that you do too. To get there, your are going to use a 1" OD guide bushing.
The first question is: How wide (not deep) of a lip do you want to leave for the plate to rest on. If you want a 1/4" lip, you are going to use a 1/2" bit (length to be determined below), since a 1/2" bit in a 1" bushing gives a 1/4" offset.
If you want a 3/8" lip, you will use a 1/4" bit, same as above except for a 3/8" offset.
Insert a 1" guide bushing into your router (no bit) then plunge the router (unplugged) until the collet almost (but not quite, very important) touches the bushing. Set your depth stop here to prevent the two from touching later.
Now we determine the minimum length of the bit, add:
* the thickness of the template (probably 3/4") and
* the thickness of the router table top (for this example, assume 1-1/2")
these add up to 2-1/4". This means that the bit must be (overall) long enough to permit your collet to get a good grip on it (assume 1" but probably about minimum for full safety, you determine). Thus the bit needs to be 3-1/4" overall.
Affix the template to your table where you are going to want the router lift installed with double-stick carpet tape. Attach a scrap of wood under the table, screwed to the table twice outside the cut (to prevent tearout at the end) and twice well inside of where the cutter will cut (to keep the cut piece from binding the bit at the end.
Make the cut in a series of steps. The first one whould be very shallow (perhaps 1/8" or so). Then repeat the cuts, each a little deeper until you get nearly through. Try to judge the last cut to be shallow to minimize tearout. Each cut depth should not exceed the diameter of the bit.
After the final cut, turn off the router and remove the scrap, leaving you with a clean through hole in your table. Remove the bit and guide. Next we cut the lip.
For this, you are going to need a cutter that is short enough that, with a bearing (same diameter as the bit) attached on top, both the bearing and the bit depth are less than or equal to the *thickness* of your template. I used a 1/4" shank, 1/2" diameter, 1/2" cutter depth hinge mortising bit (LeeValley part #16J08.08) with a 1/4" ID, 1/2" OD, 3/16" high bearing (Lee Valley #16J95.06) and a lock ring (Lee Valley 16J96.04). The plunge depth stop should be set to leave the lip a little shallow (not deep enough) so you can "sneak up on it"). Lower the bit so the bearing can run against the template, turn on the router and again make the first cut shallow, and sneak up on the depth. If you get a bit too deep, a strip of tape can be used as a shim to hold the plate flush with the table.
I've provided Lee Valley part numbers so you can look up pictures of the lip-making parts online in case my description is not clear; you can surely spend less elsewhere.
If your router takes 1-1/2" bushings, a 1/2" bit would give you a 1/2" lip with a 1-1/2" OD guide. In my case the router and lift were heavy and the plate was sized to support 1/2", so that's what I used.
I remember my nervousness in preparing to cut though my newly-constructed table top but, with the template and guide any error you make will be to cut into the waste and you can easily come back and "clean up" the slip. The same is true with the bearing, as long as you are careful to make sure it is lowered enough to press against the template as the bit aproaches.
There are undoubtedly other (and perhaps easier) ways to get there, but this worked for me.
I hope this helps!
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