Over the past decade, successive double-scratch tests have been extensively performed to study the grinding mechanism of brittle materials. However, the grits sometimes interact with the surface simultaneously. In this study, double tips with a tip separation of 0.6–1.8 μm are fabricated by focused ion beam. Subsequently, double-scratch tests on BK7 optical glass are conducted using the double-tip scratch tool with a scratch depth of 200–600 nm. The typical crack system and its evolution mechanism for double-tip scratch are discovered, before being explained using an analytical stress model. The ductile–brittle transition and the material-removal mechanism are discussed. An influential radius for the interference between cracks and the stress field in the double scratch is obtained, which can serve as a reference for the design of textured grinding wheels. Subsequently, the advantages and disadvantages of double-tip scratches are discussed considering different applications, such as microstructure fabrication and grinding.