Casting is a near-net shape process, and the casting design engineer almost always has the option of producing a feature on the component with a feature in the mold. 

One of the key features in the drive wheel is the center bore in the hub for the drive shaft. This hole has precise dimensional tolerances on the ID along with a keyway. 

The casting designer had two choices in producing this  center bore.

• Option A -- Two step machining process. After casting, using a rough drill and a finish machining operation to produce the center bore. 
  

• Option B -- A center core in the mold.  A center core in the mold produces the near-net-shape hole and a finish machine step brings the hole to final specifications.