I'm just posting this because I didn't find anything by using Google search. Using a router to cut shadow lines in ceiling tile. I'm no pro at using a utility knife to cut the recessed lines in the tiles like the pros. I even tried Toolpro shadowline cutter TP05110 with no luck. I have the thicker tiles for sound transfer. So the set guide depth on the tool was not right for my tiles. So I will be returning the Toolpro with extra blades.
So I decided to use my table saw to cut all the partial ceilings tiles around walls. Using a router table to cut the shadow lines works great for nice clean cuts. Yes it is going to create a lot of dust so you will want to do it outside. Safety glasses and dust mask will be a must. I learned to install the cut edges against the wall so I don't have to paint to match the tile. This is for my basement ceiling. I also have a walk out basement. So I don't need to go up/down stairs to make cuts.