I agree with Helomatic I do not think that is the "facing" tool. also what Dave and Chombi said are correct too if you are dealing with a Mavic cart BB (I think VO just came out with one)

now to answer your question about the too. the 'facing' cutter should not chamfer the BB shell but it is designed to remove paint and "square" the sides of the BB to ensure they are parrallel. this aids in getting the fixed cup tightly into place as well and making the lockring lock tighter. 'facing' and 'chasing' was standard practice on all frame (build up in shops anyway) and I normally did it ( atleast facing) on overhauls. there is also a tool for 'facing' the headtube as well.