marcrunner

I am starting a cabinet door project. I am working with a table mounted bosch router and a cove and bead bit w/ bearing. Everytime I try to carefully start a 4"x20" board against the bit, it violently grabs and trys to discard the board. I was under the impression that if a bit had a bearing that i did not have to have a fence? Am I wrong here? It is very easy for me to line up a fence, so that the board was being held in place. Am I supposed to be raising the bit a litlle at a time so that it doesn't have so much to take off at a time? The router has plenty of power, and the bit is new. Any ideas? thanx,Marc