The purpose of this study was to improve the grindability of titanium by alloying with zirconium. The grindability of dental cast Ti-Zr binary alloys (10, 20, 30, 40 and 50 mass%Zr) was evaluated using a carborundum wheel. The Ti-Zr alloys up to 30 mass%Zr formed an α structure, and the 40 mass%Zr and 50 mass%Zr alloys formed an α′ structure. The Ti-40 mass%Zr alloy at up to 1000 m•min−1 and the Ti-50 mass%Zr alloy at up to 1250 m•min−1 exhibited significantly higher grindability than titanium. More than twice the volume of metal was removed from the alloys than from titanium per minute. The improved grindability could be attributed to the α′ structure in addition to the decrease in elongation. The Ti-Zr alloys, which formed an α′ phase structure, are candidates for use as machinable biomaterial in dental applications.