A cutting bit and bit assembly for mounting at a cutting machine. The bit includes an axially tapered bit body having a recess extending axially within the body. The recess has an innermost region and a mouth region that is generally convex and/or tapered radially outward to abut a corresponding concave or tapered surface of a projection to secure the cutting bit at a holder body. An annular step is positioned within the recess at the mouth region to prevent dust and contaminant fluid or particles from passing axially into the recess.