Centre Drill
From DT Online
When drilling metal, it is advisable first to mark the hole centre with a Centre Punch to stop Twist Drills wandering about the surface.
When drilling down the centre of a bar held in a Lathe chuck however, a Centre Drill is used. These are short and rigid enough to mark the bar centre. In addtion, they not only drill a pilot hole, but can be used to create the countersink required to locate a lathe centre for turning between centres.