The hardened alpha-case (α-case) layer inevitably forms on the surface of titanium castings when prepared by investment casting. Because the hardness of the α-case is incomparable to that of the interior structure, the perception exists that the α-case is difficult to remove during cutting, grinding and polishing. Grindability (ease of grinding) of cast cpTi and cast Ti-6Al-4V was evaluated by grinding cast specimens incrementally using a SiC abrasive wheel. The present study revealed that the presence of the brittle α-case with lower fracture toughness is beneficial in grinding titanium. The α-case on the ductile cpTi can be ground much easier than its bulk interior structure. In less ductile Ti-6Al-4V, the grinding rate is much higher than that of cpTi, and the α-case and its interior structure are at similar levels since the fracture toughness of its α-case and the bulk material is not large enough.