Hi, you are talking about a bullnose edge. You can buy a bullnose bit to cut it in one or two passes, or you can use the very inexpensive quarter round bits that are half the depth of the thickness of the wood. For 3/4 ply, which is really 18/24 ths or 18mm (aprox), you can use a 3/8ths quarter round bit and then run the sheet over the bit on one side, flip it over and repeat on the other side. That is usually the easiest way to do it. I suggest you do it in two passes, expecially if the bit has only a 1/4 inch shaft. Cut both sides with a shallow cut, then finish with another cut the full depth to get the final effect.
Since you are using BB sheet goods, you shouldn't have any voids. I personally like that multi layer look, but make sure you seal it well because the top veneer in particular is very thin and easily nicked.
The radius you choose may depend on your intended purpose. If you are just trying to soften a sharp edge so you don't scratch your hands, then use a radius smaller than half the thickness. My local woodworking club annually makes about 500 doll beds out of 1/2" Baltic Birch plywood and we use either 1/8" or 3/16" radius round over. This gives you a soft edge so that scratches are minimized.
I would suggest cutting and gluing a 1/2" piece of hardwood along the edge first. Reason --> most plywood has voids and so you will be using wood filler a lot. Also with the solid wood edge you will lower your frustration level due to feathering and splits on the top 1mm ply.
What kind of plywood will you be doing this on? Void Free? Or something else. If voids, expect to need to fill them, let the filling dry, and then trim the edges again - don't change the bit setting until all of the second pass is complete. You will hate yourself it you change the bit and fence settings before completing the finishing pass.
I usually use Bondo for filling if the work will be painted, Water Putty, if I will be staining, but even then a touch up of the stain with a darker version of the same color may be needed to improve the match of the filler to the work.
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