Place the edge on a flat surface, holding the razor at a slight angle so the edge is touching the surface (I use a piece of wood) never, ever, ever, let the Dremel spin toward the edge, always away from the edge , spinning from spine to edge,,, Then be very, very, careful, but at least you will not wrap around the edge with the Dremel doing it this way....

I HATE DREMELS BTW !!!!! but if ya gotta use one that's the way to do it....