I'm replacing Mortise locks with contemporary levers on solid wood doors in my apartment. The doors are pine, 1 3/4" thick. I've removed the Mortise locks, leaving behind two large holes and the Mortise cut-out in the door (first photo).
My goal is to stain the doors, so I want to patch the entire area and avoid using fillers for a nice, clean look; I believe this type of patch is called a Dutchman Patch (second photo).
I purchased a low-end plunge router to cut out the area, but I'm not exactly sure what size bit is suitable to cut 1/2" deep; the area is about 4" x 7". In the video they mention "upwards spiraling" bit, I'm assuming this means "up-cut", I'm just not sure what shank size and bit diameter is suitable for cutting this area effectively, cleanly, and without me standing there for an hour; I have to make 9 of these, correction, 18 (doors have two sides :-D )
What shank size and bit diameter is suitable for cutting out the area for the patch?