Right but there are in general two kinds of circular saw, one that cut
as a row of chissels -- the one to use -- and one made to cut wood
across the grains -- the one not to use.
Ther are offcaurse combinations but the even with a wide tooth in hard
metal you maby only make a notch of 2 millimeter , then it is nicer
with the router as with that you just put a small piece in btween or
adjust so the notch get the right size.